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Purpose: Deleterious germline variants in certain DNA repair genes are risk factors for developing aggressive prostate cancer. The objective was to quantify their prognostic impact after prostate cancer diagnosis., Methods: Men with prostate cancer, predominantly of European ancestry, were included from four cohorts with long-term follow-up. Pathogenic or likely pathogenic germline variants in 26 DNA repair genes were assessed in relation to metastasis-free survival in high-risk, localized prostate cancer and to overall survival in metastatic castration-sensitive prostate cancer (mCSPC) and metastatic castration-resistant prostate cancer (mCRPC)., Results: Among 3,525 patients initially diagnosed with non-metastatic prostate cancer, 2,594 had high-risk localized prostate cancer, 429 mCSPC, and 502 mCRPC at inclusion. BRCA2 variant carriers did not have worse metastasis-free survival in high-risk localized prostate cancer (hazard ratio [HR] 1.01, 95% confidence interval [CI] 0.69, 1.46) or overall survival in mCSPC (HR 0.46, 95% CI 0.14, 1.45) or mCRPC (HR 0.60, 95% CI 0.31, 1.17) compared to non-carriers of DNA repair variants. Among 868 additional patients with de novo metastatic (M1) prostate cancer, BRCA2 variant carriers tended to have worse overall survival (HR 1.59, 95% CI 1.01, 2.51). BRCA2 prognostic associations were not explained by radiation, PARP inhibitor, or platinum therapy. Results for other genes were limited in precision because variants were less common., Conclusions: Among patients with high-risk or metastatic prostate cancer who were initially diagnosed with and treated for non-metastatic tumors, germline DNA repair variants in BRCA2 do not confer a substantially worse prognosis.

Background/objectives: Unfortunately, not all metastatic castration resistant prostate cancer (mCRPC) patients receive available life-prolonging systemic therapies, emphasizing the need to optimize mCRPC treatment selections. Better guidelines are necessary to determine genetic testing in prostate cancer., Subjects/methods: In this two-part expert opinion-based guide, we provide an expert consensus opinion on the utilization of germline and somatic testing to detect HRR alterations in patients with mCRPC. This guide was developed by a multidisciplinary expert panel that convened in 2023-2024, including representatives from medical oncology, urology, radiation oncology, pathology, medical genomics, and basic science., Results/conclusion: We argue for the widespread adoption of germline testing in all patients with prostate cancer and for somatic mutations testing in patients at the time of recurrent/metastatic disease. In this first part, we review how genomic testing is performed. We also review how to overcome certain barriers to integrate genetic and biomarker testing into clinical practice., (© 2024. The Author(s).)

Background/objectives: Unfortunately, not all metastatic castration-resistant prostate cancer (mCRPC) patients receive available life-prolonging systemic therapies, emphasizing the need to optimize mCRPC treatment selections. Better guidelines are necessary to determine genetic testing for prostate cancer., Subjects/methods: In this two-part expert opinion-based guide, we provide an expert consensus opinion on the utilization of germline and somatic testing to detect HRR alterations in patients with mCRPC. This guide was developed by a multidisciplinary expert panel that convened in 2023-2024, including representatives from medical oncology, urology, radiation oncology, pathology, medical genomics, and basic science., Results/conclusions: In this second part, we highlight how genetic testing can lead to improved, life-prolonging mCRPC therapeutic strategies based on a review of the recent phase III trials and subsequent regulatory approvals for PARP inhibitors in mCRPC., (© 2024. The Author(s).)

Purpose: CDK12 is a cyclin-dependent kinase (CDK) that is mutated or amplified in multiple cancers. We previously described a subtype of prostate cancer (PC) characterized predominantly by frameshift, loss-of-function mutations in CDK12. This subtype exhibits aggressive clinical features., Experimental Design: Using isogenic PC models generated by CRISPR/Cas9-mediated inactivation of CDK12, we conducted a chemical library screen of ~1800 FDA-approved drugs. We inhibited cyclin K and CDK13 and evaluated the effects on poly ADP-ribose polymerase inhibitor (PARPi) sensitivity. CDK12 truncation and kinase domain mutations were expressed in cell lines to determine effects on PARPi sensitivity. Mice bearing control and CDK12 mutant prostate tumors were treated with rucaparib. Finally, we evaluated prostate specific antigen (PSA) responses in patients with CDK12 mutations treated with rucaparib on the TRITON2 trial., Results: Cancer cells lacking CDK12 are more sensitive to PARPi than isogenic wild-type cells, and sensitivity depends on the degree of CDK12 inhibition. Inhibiting cyclin K, but not CDK13, also led to PARPi sensitivity and suppressed homologous recombination. CDK12 truncation mutants remained sensitive to PARPi, whereas kinase domain mutants exhibited intermediate sensitivity. The PARPi rucaparib suppressed tumor growth in mice bearing CDK12-mutated tumors. Finally, 6 of 11 (55%) PC patients with biallelic CDK12 mutations had reductions in serum PSA levels when treated with rucaparib on the TRITON2 clinical trial., Conclusions: In PC, sensitivity to PARPi is dependent on the specific type and zygosity of the CDK12 mutation. PARPi monotherapy may have some activity in PC patients with biallelic inactivating CDK12 alterations.

Purpose: Patients with microsatellite instability-high/mismatch repair-deficient (MSI-H/dMMR) and high tumor mutational burden (TMB-H) prostate cancers are candidates for pembrolizumab. We define the genomic features, clinical course, and response to immune checkpoint blockade (ICB) in patients with MSI-H/dMMR and TMB-H prostate cancers without MSI [TMB-H/microsatellite stable (MSS)]., Experimental Design: We sequenced 3,244 tumors from 2,257 patients with prostate cancer. MSI-H/dMMR prostate cancer was defined as an MSIsensor score ≥10 or MSIsensor score ≥3 and <10 with a deleterious MMR alteration. TMB-H was defined as ≥10 mutations/megabase. PSA50 and RECIST responses were assigned. Overall survival and radiographic progression-free survival (rPFS) were compared using log-rank test., Results: Sixty-three (2.8%) men had MSI-H/dMMR, and 33 (1.5%) had TMB-H/MSS prostate cancers. Patients with MSI-H/dMMR and TMB-H/MSS tumors more commonly presented with grade group 5 and metastatic disease at diagnosis. MSI-H/dMMR tumors had higher TMB, indel, and neoantigen burden compared with TMB-H/MSS. Twenty-seven patients with MSI-H/dMMR and 8 patients with TMB-H/MSS tumors received ICB, none of whom harbored polymerase epsilon (polE) catalytic subunit mutations. About 45% of patients with MSI-H/dMMR had a RECIST response, and 65% had a PSA50 response. No patient with TMB-H/MSS had a RECIST response, and 50% had a PSA50 response. rPFS tended to be longer in patients with MSI-H/dMMR than in patients with TMB-H/MSS who received immunotherapy. Pronounced differences in genomics, TMB, or MSIsensor score were not detected between MSI-H/dMMR responders and nonresponders., Conclusions: MSI-H/dMMR prostate cancers have greater TMB, indel, and neoantigen burden than TMB-H/MSS prostate cancers, and these differences may contribute to profound and durable responses to ICB., (©2024 American Association for Cancer Research.)

Higher levels of aneuploidy, characterized by imbalanced chromosome numbers, are associated with lethal progression in prostate cancer. However, how aneuploidy contributes to prostate cancer aggressiveness remains poorly understood. In this study, we assessed in patients which genes on chromosome 8q, one of the most frequently gained chromosome arms in prostate tumors, were most strongly associated with long-term risk of cancer progression to metastases and death from prostate cancer (lethal disease) in 403 patients and found the strongest candidate was cohesin subunit gene, RAD21 , with an odds ratio of 3.7 (95% CI 1.8, 7.6) comparing the highest vs. lowest tertiles of mRNA expression and adjusting for overall aneuploidy burden and Gleason score, both strong prognostic factors in primary prostate cancer. Studying prostate cancer driven by the TMPRSS2-ERG oncogenic fusion, found in about half of all prostate tumors, we found that increased RAD21 alleviated toxic oncogenic stress and DNA damage caused by oncogene expression. Data from both organoids and patients indicate that increased RAD21 thereby enables aggressive tumors to sustain tumor proliferation, and more broadly suggests one path through which tumors benefit from aneuploidy., Competing Interests: Competing interests statement:M.G.V.H. discloses that he is a scientific advisor for Agios Pharmaceuticals, Auron Therapeutics, iTeos Therapeutics, Droia Ventures, Lime Therapeutics, Pretzel Therapeutics, and Sage Therapeutics. L.A.M. reports research funding from Janssen and Astra Zeneca; serves on the scientific advisory board and holds equity interest in Convergent Therapeutics; and was a consultant to Bayer Pharmaceuticals. W.A. discloses honoraria from Roche, Medscape, Aptitude Health, Clinical Education Alliance, OncLive/MJH Life Sciences, touchIME, Pfizer, theMedNet; serves as a consulting or advisory role in Clovis Oncology, Janssen, Overcoming Resistance In Cancer (ORIC) Pharmaceuticals, Daiichi Sankyo, AstraZeneca/MedImmune, Pfizer, Laekna Therapeutics, MOMA Therapeutics, Endeavor BioMedicines.

Purpose: CDK12 inactivation in metastatic castration-resistant prostate cancer (mCRPC) may predict immunotherapy responses. This phase 2 trial evaluated the efficacy of immune checkpoint inhibitor (ICI) therapy in patients with CDK12-altered mCRPC., Patients and Methods: Eligible patients had mCRPC with deleterious CDK12 alterations and any prior therapies except ICI. Cohort A received ipilimumab (1 mg/kg) with nivolumab (3 mg/kg) every 3 weeks for up to four cycles, followed by nivolumab 480 mg every 4 weeks. Cohort C received nivolumab alone 480 mg every 4 weeks. Patients with CDK12-altered nonprostate tumors were enrolled in cohort B and not reported. The primary endpoint was a 50% reduction in PSA (PSA50). Key secondary endpoints included PSA progression-free survival, overall survival, objective response rate, and safety., Results: PSA was evaluable in 23 patients in cohort A and 14 in cohort C. Median lines of prior therapy were two in cohorts A and C, including any prior novel hormonal agent (74% and 79%) and chemotherapy (57% and 36%). The PSA50 rate was 9% [95% confidence interval (CI), 1%-28%] in cohort A with two responders; neither had microsatellite instability or a tumor mutational burden >10 mutations/megabase. No PSA50 responses occurred in cohort C. Median PSA progression-free survival was 7.0 months (95% CI, 3.6-11.4) in cohort A and 4.5 months (95% CI, 3.4-13.8) in cohort C. Median overall survival was 9.0 months (95% CI, 6.2-12.3) in cohort A and 13.8 months (95% CI, 3.6-not reached) in cohort C., Conclusions: There was minimal activity with ICI therapy in patients with CDK12-altered mCRPC., (©2024 American Association for Cancer Research.)

Purpose: Increased glucocorticoid receptor (GR) signaling is a proposed compensatory mechanism of resistance to androgen receptor (AR) inhibition in metastatic castration-resistant prostate cancer (mCRPC). ORIC-101 is a potent and selective orally-bioavailable GR antagonist., Patients and Methods: Safety, pharmacokinetic/pharmacodynamic, and antitumor activity of ORIC-101 in combination with enzalutamide were studied in patients with mCRPC progressing on enzalutamide. ORIC-101 doses ranging from 80 to 240 mg once daily were tested in combination with enzalutamide 160 mg once daily. Pharmacokinetics/pharmacodynamics was assessed after a single dose and at steady state. Disease control rate (DCR) at 12 weeks was evaluated at the recommended phase 2 dose (RP2D)., Results: A total of 41 patients were enrolled. There were no dose-limiting toxicities and the RP2D was selected as 240 mg of ORIC-101 and 160 mg of enzalutamide daily. At the RP2D, the most common treatment-related adverse events were fatigue (38.7%), nausea (29.0%), decreased appetite (19.4%), and constipation (12.9%). Pharmacokinetic/pharmacodynamic data confirmed ORIC-101 achieved exposures necessary for GR target engagement. Overall, for 31 patients treated at the RP2D, there was insufficient clinical benefit based on DCR (25.8%; 80% confidence interval: 15.65-38.52) which did not meet the prespecified target rate, leading to termination of the study. Exploratory subgroup analyses based on baseline GR expression, presence of AR resistance variants, and molecular features of aggressive variant prostate cancer suggested possible benefit in patients with high GR expression and no other resistance markers, although this would require confirmation., Conclusions: Although the combination of ORIC-101 and enzalutamide demonstrated an acceptable tolerability profile, GR target inhibition with ORIC-101 did not produce clinical benefit in men with metastatic prostate cancer resistant to enzalutamide., (©2024 American Association for Cancer Research.)

Reversion mutations that restore wild-type function of the BRCA gene have been described as a key mechanism of resistance to Poly(ADP-ribose) polymerase (PARP) inhibitor therapy in BRCA-associated cancers. Here, we report a case of a patient with metastatic castration-resistant prostate cancer (mCRPC) with a germline BRCA2 mutation who developed acquired resistance to PARP inhibition. Extensive genomic interrogation of cell-free DNA (cfDNA) and tissue at baseline, post-progression, and postmortem revealed ten unique BRCA2 reversion mutations across ten sites. While several of the reversion mutations were private to a specific site, nine out of ten tumors contained at least one mutation, suggesting a powerful clonal selection for reversion mutations in the presence of therapeutic pressure by PARP inhibition. Variable cfDNA shed was seen across tumor sites, emphasizing a potential shortcoming of cfDNA monitoring for PARPi resistance. This report provides a genomic portrait of the temporal and spatial heterogeneity of prostate cancer under the selective pressure of a PARP inhibition and exposes limitations in the current strategies for detection of reversion mutations., (© 2024. The Author(s).)

Background: CC-115, a dual mTORC1/2 and DNA-PK inhibitor, has promising antitumour activity when combined with androgen receptor (AR) inhibition in pre-clinical models., Methods: Phase 1b multicentre trial evaluating enzalutamide with escalating doses of CC-115 in AR inhibitor-naive mCRPC patients (n = 41). Primary endpoints were safety and RP2D. Secondary endpoints included PSA response, time-to-PSA progression, and radiographic progression., Results: Common adverse effects included rash (31.7% Grades 1-2 (Gr); 31.7% Gr 3), pruritis (43.9% Gr 1-2), diarrhoea (37% Gr 1-2), and hypertension (17% Gr 1-2; 9.8% Gr 3). CC-115 RP2D was 5 mg twice a day. In 40 evaluable patients, 80% achieved ≥50% reduction in PSA (PSA50), and 58% achieved ≥90% reduction in PSA (PSA90) by 12 weeks. Median time-to-PSA progression was 14.7 months and median rPFS was 22.1 months. Stratification by PI3K alterations demonstrated a non-statistically significant trend towards improved PSA50 response (PSA50 of 94% vs. 67%, p = 0.08). Exploratory pre-clinical analysis suggested CC-115 inhibited mTOR pathway strongly, but may be insufficient to inhibit DNA-PK at RP2D., Conclusions: The combination of enzalutamide and CC-115 was well tolerated. A non-statistically significant trend towards improved PSA response was observed in patients harbouring PI3K pathway alterations, suggesting potential predictive biomarkers of response to a PI3K/AKT/mTOR pathway inhibitor., Clinical Trial Registration: ClinicalTrials.gov identifier: NCT02833883., (© 2023. The Author(s), under exclusive licence to Springer Nature Limited.)

Introduction:  Use of the Patient-Reported Outcomes version of the Common Terminology Criteria for Adverse Events (PRO-CTCAE) during chemotherapy is associated with decreased hospitalization rates, improved quality of life, and longer survival. Limited data exist on the benefit of this symptom assessment tool for monitoring immune-related adverse events (irAEs)., Methods:  We incorporated irAE-related items from the National Cancer Institute's (NCI) PRO-CTCAE in a trial evaluating ipilimumab in combination with androgen deprivation therapy in 16 patients with hormone-sensitive prostate cancer. For comparison, NCI's CTCAE version 4.0 was used by clinicians., Results:  IrAE-related PRO-CTCAE surveys and matched CTCAEs (184 pairs) reporting abdominal pain, diarrhea, fatigue, anorexia, nausea, vomiting, rash, and pruritus were collected at each treatment administration and during follow-up. Fatigue, diarrhea, rash, and pruritus were the symptoms most frequently reported by both patients and clinicians. Agreement was lowest for pruritus (κ = 0.10) and highest for rash (κ = 0.64). IrAEs were more commonly reported and of higher grade with PRO-CTCAE scores compared with CTCAE grades., Conclusion:  PRO-CTCAEs focused on irAEs capture the patient's immunotherapy experience while complementing the clinician's toxicity assessment measures. Further study is needed to assess PRO-CTCAE's utility in identifying and managing irAEs., Competing Interests: Conflict of Interest: Daniel Vargas P. de Almeida reports speaker compensation from Astellas, AstraZeneca, Bayer, Eli Lilly, Janssen-Cilag, and Sanofi-Aventis. Daniel C. Danila reports research support from US Department of Defense, American Society of Clinical Oncology, Prostate Cancer Foundation, Stand Up to Cancer, Janssen Research & Development, Agensys, Genentech, CreaTV; consultant for Angle LLT, Axiom LLT, Janssen Research & Development, AstraZeneca, BioView LTD, Clovis, Astellas, Medivation, Pfizer, and Agensys. Michael J. Morris reports travel support from Endocyte, Fujifilm; research funding (to institution) from Novartis, Bayer, Celgene, Corcept, Roche/Genentech, Janssen; is an uncompensated consultant to Bayer, Novartis, Johnson and Johnson; is a compensated consultant to Oric, Lantheus, Curium, AstraZeneca, Amgen, Daiichi, Convergent Therapeutics, Pfizer, and ITM Isotope Technologies. Wassim Abida reports speaking honoraria from Roche, Medscape, Aptitude Health, Clinical Education Alliance, MJH Life Sciences and touchIME, consulting fees from Clovis Oncology, Janssen, ORIC Pharmaceuticals, Daiichi Sankyo and AstraZeneca UK, and research funding (to institution) from AstraZeneca, Zenith Epigenetics, Clovis Oncology, Glaxo-Smith Kline, and ORIC Pharmaceuticals. Howard I. Scher reports compensated consultant/advisor to Ambry Genetics Corp, Konica Minolta Inc, Bayer, Pfizer Inc, Sun Pharmaceuticals, WCG Oncology; uncompensated consultant/advisory to Amgen, Janssen Research & Development, LLC, Janssen Biotech, Inc,; honoraria from Arsenal Capital; has received research funding (to institution) from AIQ Solutions, Epic Sciences, Illumina, Inc, Janssen, Menarini Silicon Biosystems, Prostate Cancer Foundation and ThermoFisher; supported in part by NIH/NCI grant P50 CA092629 (MSK SPORE in Prostate Cancer); intellectual property rights BioNTech, Elucida Oncology, MaBVAX, Y-mAbs Therapeutics, Inc.; non-financial support from Amgen, Bayer, Epic Sciences, Promontory Therapeutics (formerly Phosplatin), Pfizer Inc, Prostate Cancer Foundation, and WCG Oncology. Karen A. Autio reports research funding (to institution) from Pfizer, Amgen, Trishula, CytomX, Astra-Zeneca, Eli Lilly, Glaxo-Smith Kline, and Parker Institute for Cancer Immunotherapy. The remaining authors have no disclosures, (© This work is published under a CC-BY-NC-ND 4.0 International License.)

Background: Initial TRITON2 (NCT02952534) results demonstrated the efficacy of rucaparib 600 mg BID in patients with metastatic castration-resistant prostate cancer (mCRPC) associated with a BRCA1 or BRCA2 (BRCA) or other DNA damage repair (DDR) gene alteration., Objective: To present the final data from TRITON2., Design, Setting, and Participants: TRITON2 enrolled patients with mCRPC who had progressed on one or two lines of next-generation androgen receptor-directed therapy and one taxane-based chemotherapy., Outcome Measurements and Statistical Analysis: The primary endpoint was objective response rate (ORR; as per the modified Response Evaluation Criteria in Solid Tumor Version 1.1/Prostate Cancer Clinical Trials Working Group 3 criteria in patients with measurable disease by independent radiology review [IRR]); prostate-specific antigen (PSA) response rate (≥50% decrease from baseline [PSA50]) was a key secondary endpoint., Results and Limitations: As of July 27, 2021 (study closure), TRITON2 had enrolled 277 patients, grouped by mutated gene: BRCA (n = 172), ATM (n = 59), CDK12 (n = 15), CHEK2 (n = 7), PALB2 (n = 11), or other DDR gene (Other; n = 13). ORR by IRR was 46% (37/81) in the BRCA subgroup (95% confidence interval [CI], 35-57%), 100% (4/4) in the PALB2 subgroup (95% CI, 40-100%), and 25% (3/12) in the Other subgroup (95% CI, 5.5-57%). No patients within the ATM, CDK12, or CHEK2 subgroups had an objective response by IRR. PSA50 response rates (95% CI) in the BRCA, PALB2, ATM, CDK12, CHEK2, and Other subgroups were 53% (46-61%), 55% (23-83%), 3.4% (0.4-12), 6.7% (0.2-32%), 14% (0.4-58%), and 23% (5.0-54%), respectively., Conclusions: The final TRITON2 results confirm the clinical benefit and manageable safety profile of rucaparib in patients with mCRPC, including those with an alteration in BRCA or select non-BRCA DDR gene., Patient Summary: Almost half of TRITON2 patients with BRCA-mutated metastatic castration-resistant prostate cancer had a complete or partial tumor size reduction with rucaparib; clinical benefits were also observed with other DNA damage repair gene alterations., (Crown Copyright © 2023. Published by Elsevier B.V. All rights reserved.)

Competing Interests: WA received speaking honoraria from Roche, Medscape, Aptitude Health, Clinical Education Alliance, OncLive/MJH Life Sciences, and touchIME; consulting fees from Clovis Oncology, Janssen, ORIC Pharmaceuticals, Daiichi Sankyo, and AstraZeneca; and royalties from UptoDate and research funding to his institution from AstraZeneca, Zenith Epigenetics, Clovis Oncology, ORIC Pharmaceuticals, and Epizyme. Some of the consulting activities, speaking honoraria, and research funding are related to PARP inhibitor use in prostate cancer. WA receives research funding from the National Cancer Institute (NCI) Cancer Center Support grant number P30-CA008748, NCI Prostate Specialized Program of Research Excellence (SPORE) grant number P50-CA092629-16, and the Prostate Cancer Foundation. GA is on the steering committees of the MAGNITUDE and AMPLITUDE trials sponsored by Janssen and is a Principal Investigator of clinical trials sponsored by Janssen, Pfizer (PROSPER, NCT02003924), and Novartis. GA has received consulting fees from Janssen, Pfizer, AstraZeneca, and Clovis and speaker fees from AstraZeneca and Janssen to speak on prostate cancer, including regarding PARP inhibitors. GA has participated in advisory boards for Janssen, Pfizer, Astra Zeneca, and Clovis on topics related to prostate cancer, including PARP inhibition. GA has received research grants to their institution from Janssen, Astellas, and Novartis for subjects related to prostate cancer. GA has also received consulting fees from Novartis, Bayer, Blue Earth Therapeutics, Boehringer, and Roche, which are companies with drugs in development for prostate cancer; and receives a share of the royalty income from The Institute of Cancer Research Rewards to Discoverers Scheme for abiraterone as personal royalties. GA holds a patent on plasma methylation signatures as biomarkers for prostate cancer (GB1915469.9). This patent is held by funders (Cancer Research UK). GA is listed as an inventor and could receive a share of commercial revenue via their institution University College London. This patent is not related to this study or PARP inhibitors but is a blood test that is being developed for the diagnosis or risk stratification of prostate cancer.

Purpose: Genetic testing may alter clinical management for individuals with metastatic prostate cancer by identifying additional therapies. Traditional counseling models are unlikely to enable time-sensitive therapeutic decision-making. This study aimed to determine the feasibility and clinical impact of an alternative hereditary genetic testing model., Materials and Methods: As part of a multicenter, single-arm prospective trial, individuals with advanced prostate cancer were referred by their oncologist for testing of 14 genes associated with hereditary prostate cancer. Pretest education (brochure and video) was provided in the oncology clinic. Questionnaires assessing participant satisfaction with both pretest education and decision to undergo genetic testing were collected. A genetic counselor contacted participants by phone to obtain family history and discuss results. Medical records were queried to determine whether a change in clinical management was discussed., Results: Of 501 participants consented to germline analysis, 51 (10.2%) had at least 1 pathogenic/likely pathogenic variant. Change in treatment was discussed with 22/48 (45.8%) of eligible participants who tested positive. Feasibility of this model was assessed by participant satisfaction and turnaround time. Average±SD satisfaction with the pretest education (15.5±2.2, 4-20 scale) and with the decision to undergo genetic testing (17.1±2.9, 4-20 scale) were both high. Results were returned 20 days (median) after sample collection., Conclusions: Oncologist-initiated germline genetic testing in collaboration with a genetic counselor is a feasible approach to testing advanced prostate cancer patients with impactful clinical actionability. The testing model and educational material serve as resources to clinicians treating prostate cancer patients.

Background: Poly(adenosine diphosphate-ribose) polymerase (PARP) inhibitors are approved in the USA for the treatment of patients with BRCA1 or BRCA2 (BRCA) mutated (BRCA+) metastatic castration-resistant prostate cancer (mCRPC). BRCA reversion mutations are a known mechanism of acquired resistance to PARP inhibitors in multiple cancer types, although their impact and prevalence in mCRPC remain unknown., Objective: To examine the prevalence of BRCA reversion mutations in the plasma of patients with BRCA+ mCRPC after progression on rucaparib., Design, Setting, and Participants: Men with BRCA+ mCRPC enrolled in Trial of Rucaparib in Prostate Indications 2 (TRITON2) were treated with rucaparib after progressing on one to two lines of androgen receptor-directed and one taxane-based therapy. Cell-free DNA from the plasma of 100 patients, collected at the end of treatment after confirmed progression before May 5, 2020, was queried for BRCA reversion mutations using next-generation sequencing (NGS)., Outcome Measurements and Statistical Analysis: The association of clinical efficacy and postprogression genomics was measured in 100 patients with BRCA+ mCRPC treated with rucaparib., Results and Limitations: No baseline BRCA reversion mutations were observed in 100 BRCA+ patients. NGS identified somatic BRCA reversion mutations in 39% (39/100) of patients after progression. Reversion rates were similar for BRCA2 and BRCA1, irrespective of germline or somatic status, but higher in samples with a high tumor DNA fraction. Most patients with reversions (74%, 29/39) had two or more reversion mutations occurring subclonally at lower allele frequencies than the original BRCA mutations. The incidence of BRCA reversion mutations increased with the duration of rucaparib treatment. The frequency of reversion mutations was higher in patients with an objective (58%) or a prostate-specific antigen (69%) response compared with those without either (39% and 29%, respectively)., Conclusions: These findings suggest that BRCA reversion mutations are a significant mechanism of acquired resistance to rucaparib in patients with BRCA+ mCRPC, with evidence of subclonal convergence promoting systemic resistance., Patient Summary: Men with BRCA mutated metastatic castration-resistant prostate cancer enrolled in TRITON2 were treated with rucaparib after progressing on one to two lines of androgen receptor-directed and one taxane-based therapy. Cell-free DNA from the plasma of 100 patients, collected after radiographic or prostate-specific antigen progression before May 5, 2020, was analyzed by next-generation sequencing and queried for BRCA reversion mutations., (Copyright © 2022 European Association of Urology. Published by Elsevier B.V. All rights reserved.)

Background: In a phase 2 study, rucaparib, an inhibitor of poly(ADP-ribose) polymerase (PARP), showed a high level of activity in patients who had metastatic, castration-resistant prostate cancer associated with a deleterious BRCA alteration. Data are needed to confirm and expand on the findings of the phase 2 study., Methods: In this randomized, controlled, phase 3 trial, we enrolled patients who had metastatic, castration-resistant prostate cancer with a BRCA1 , BRCA2 , or ATM alteration and who had disease progression after treatment with a second-generation androgen-receptor pathway inhibitor (ARPI). We randomly assigned the patients in a 2:1 ratio to receive oral rucaparib (600 mg twice daily) or a physician's choice control (docetaxel or a second-generation ARPI [abiraterone acetate or enzalutamide]). The primary outcome was the median duration of imaging-based progression-free survival according to independent review., Results: Of the 4855 patients who had undergone prescreening or screening, 270 were assigned to receive rucaparib and 135 to receive a control medication (intention-to-treat population); in the two groups, 201 patients and 101 patients, respectively, had a BRCA alteration. At 62 months, the duration of imaging-based progression-free survival was significantly longer in the rucaparib group than in the control group, both in the BRCA subgroup (median, 11.2 months and 6.4 months, respectively; hazard ratio, 0.50; 95% confidence interval [CI], 0.36 to 0.69) and in the intention-to-treat group (median, 10.2 months and 6.4 months, respectively; hazard ratio, 0.61; 95% CI, 0.47 to 0.80; P<0.001 for both comparisons). In an exploratory analysis in the ATM subgroup, the median duration of imaging-based progression-free survival was 8.1 months in the rucaparib group and 6.8 months in the control group (hazard ratio, 0.95; 95% CI, 0.59 to 1.52). The most frequent adverse events with rucaparib were fatigue and nausea., Conclusions: The duration of imaging-based progression-free survival was significantly longer with rucaparib than with a control medication among patients who had metastatic, castration-resistant prostate cancer with a BRCA alteration. (Funded by Clovis Oncology; TRITON3 ClinicalTrials.gov number, NCT02975934.)., (Copyright © 2023 Massachusetts Medical Society.)

Background: BRCA2 alterations predict for a response to poly-ADP-ribose polymerase inhibition in metastatic castration-resistant prostate cancer (mCRPC). However, detection is hindered by insufficient tumor tissue and low sensitivity of cell-free DNA for detecting copy number loss., Objective: To evaluate the BRCA2 loss detection using single-cell, shallow whole-genome sequencing (sWGS) of circulating tumor cells (CTCs) in patients with mCRPC., Design, Setting, and Participants: We analyzed CTC samples collected concurrently with tumor biopsies intended for clinical sequencing in patients with progressing mCRPC., Outcome Measurements and Statistical Analysis: Differences in proportions were evaluated using the chi-square test. Correlations between assays were analyzed in linear regression models. Associations between alterations and genomic instability were assessed on the single-cell level using mixed-effect negative binomial models., Results and Limitations: We identified 138 patients with concurrent CTC and biopsy samples. CTC sWGS generated copy number profiles in a similar proportion of patients to biopsy samples (83% vs 78%, p = 0.23), but was more effective than bone biopsies (79% vs 50%; p = 0.009). CTC sWGS detected BRCA2 loss in more patients than tissue at the ≥1 (42% vs 16%; p < 0.001) and ≥2 (27% vs 16%; p = 0.028) CTC thresholds. The overall prevalence of BRCA2 loss was not increased in CTCs using sample-level composite z scores (p = 0.4), but was significantly increased compared with a lower-than-expected prevalence in bone samples (21% vs 3%, p = 0.014). Positive/negative predictive values for CTC BRCA2 loss were 89%/96% using the ≥1 CTC threshold and 67%/92% using the composite z score. CTC BRCA2 loss was associated with higher genomic instability in univariate (1.4-fold large-scale transition difference, 95% confidence interval [CI]: 1.2-1.6; p < 0.001) and multivariable analysis (1.4-fold difference, 95% CI: 1.2-1.6; p < 0.001)., Conclusions: Copy number profiles can reliably be generated using CTC sWGS, which detected a majority of tissue-confirmed BRCA2 loss and "CTC-only" losses. BRCA2 losses were supported by increases in genomic instability., Patient Summary: Current testing strategies have limitations in their ability to detect BRCA2 loss, a relatively common alteration in prostate cancer that is used to identify patients who may benefit from targeted therapy. In this paper, we evaluated whether we could detect BRCA2 loss in individual tumor cells isolated from patient blood samples and found this method to be suitable for further analysis., (Copyright © 2022. Published by Elsevier B.V.)

Background: Tumor-only genomic profiling is an important tool in therapeutic management of men with prostate cancer. Since clinically actionable germline variants may be reflected in tumor profiling, it is critical to identify which variants have a higher risk of being germline in origin to better counsel patients and prioritize genetic testing., Objective: To determine when variants found on tumor-only sequencing of prostate cancers should prompt confirmatory germline testing., Design, Setting, and Participants: Men with prostate cancer who underwent both tumor and germline sequencing at Memorial Sloan Kettering Cancer Center from January 1, 2015 to January 31, 2020 were evaluated., Outcome Measurements and Statistical Analysis: Tumor and germline profiles were analyzed for pathogenic and likely pathogenic ("pathogenic") variants in 60 moderate- or high-penetrance genes associated with cancer predisposition. The germline probability (germline/germline + somatic) of a variant was calculated for each gene. Clinical and pathologic factors were analyzed as potential modifiers of germline probability., Results and Limitations: Of the 1883 patients identified, 1084 (58%) had a somatic or germline pathogenic variant in one of 60 cancer susceptibility genes, and of them, 240 (22%) had at least one germline variant. Overall, the most frequent variants were in TP53, PTEN, APC, BRCA2, RB1, ATM, and CHEK2. Variants in TP53, PTEN, or RB1 were identified in 746 (40%) patients and were exclusively somatic. Variants with the highest germline probabilities were in PALB2 (69%), MITF (62%), HOXB13 (60%), CHEK2 (55%), BRCA1 (55%), and BRCA2 (47%), and the overall germline probability of a variant in any DNA damage repair gene was 40%. Limitations were that most of the men included in the cohort had metastatic disease, and different thresholds for pathogenicity exist for somatic and germline variants., Conclusions: Of patients with pathogenic variants found on prostate tumor sequencing, 22% had clinically actionable germline variants, for which the germline probabilities varied widely by gene. Our results provide an evidenced-based clinical framework to prioritize referral to genetic counseling following tumor-only sequencing., Patient Summary: Patients with advanced prostate cancer are recommended to have germline genetic testing. Genetic sequencing of a patient's prostate tumor may also identify certain gene variants that are inherited. We found that patients who had variants in certain genes, such as ones that function in DNA damage repair, identified in their prostate tumor sequencing, had a high risk for having an inherited cancer syndrome., (Copyright © 2022 European Association of Urology. Published by Elsevier B.V. All rights reserved.)

Purpose: Oncogenic alterations of the PI3K/AKT pathway occur in >40% of patients with metastatic castration-resistant prostate cancer, predominantly via PTEN loss. The significance of other PI3K pathway components in prostate cancer is largely unknown., Experimental Design: Patients in this study underwent tumor sequencing using the MSK-IMPACT clinical assay to capture single-nucleotide variants, insertions, and deletions; copy-number alterations; and structural rearrangements, or were profiled through The Cancer Genome Atlas. The association between PIK3R1 alteration/expression and survival was evaluated using univariable and multivariable Cox proportional-hazards regression models. We used the siRNA-based knockdown of PIK3R1 for functional studies. FDG-PET/CT examinations were performed with a hybrid positron emission tomography (PET)/CT scanner for some prostate cancer patients in the MSK-IMPACT cohort., Results: Analyzing 1,417 human prostate cancers, we found a significant enrichment of PIK3R1 alterations in metastatic cancers compared with primary cancers. PIK3R1 alterations or reduced mRNA expression tended to be associated with worse clinical outcomes in prostate cancer, particularly in primary disease, as well as in breast, gastric, and several other cancers. In prostate cancer cell lines, PIK3R1 knockdown resulted in increased cell proliferation and AKT activity, including insulin-stimulated AKT activity. In cell lines and organoids, PIK3R1 loss/mutation was associated with increased sensitivity to AKT inhibitors. PIK3R1-altered patient prostate tumors had increased uptake of the glucose analogue 18F-fluorodeoxyglucose in PET imaging, suggesting increased glycolysis., Conclusions: Our findings describe a novel genomic feature in metastatic prostate cancer and suggest that PIK3R1 alteration may be a key event for insulin-PI3K-glycolytic pathway regulation in prostate cancer., (©2022 American Association for Cancer Research.)

Background: Routine clinical data from clinical charts are indispensable for retrospective and prospective observational studies and clinical trials. Their reproducibility is often not assessed. We developed a prostate cancer-specific database for clinical annotations and evaluated data reproducibility., Methods: For men with prostate cancer who had clinical-grade paired tumor-normal sequencing at a comprehensive cancer center, we performed team-based retrospective data collection from the electronic medical record using a defined source hierarchy. We developed an open-source R package for data processing. With blinded repeat annotation by a reference medical oncologist, we assessed data completeness, reproducibility of team-based annotations, and impact of measurement error on bias in survival analyses., Results: Data elements on demographics, diagnosis and staging, disease state at the time of procuring a genomically characterized sample, and clinical outcomes were piloted and then abstracted for 2261 patients (with 2631 samples). Completeness of data elements was generally high. Comparing to the repeat annotation by a medical oncologist blinded to the database (100 patients/samples), reproducibility of annotations was high; T stage, metastasis date, and presence and date of castration resistance had lower reproducibility. Impact of measurement error on estimates for strong prognostic factors was modest., Conclusions: With a prostate cancer-specific data dictionary and quality control measures, manual clinical annotations by a multidisciplinary team can be scalable and reproducible. The data dictionary and the R package for reproducible data processing are freely available to increase data quality and efficiency in clinical prostate cancer research., (© 2022 Wiley Periodicals LLC.)

Context: Several studies have investigated selection and sequencing of systemic agents to manage recurrent prostate cancer following local definitive treatment., Objective: To define the incidence of recurrent prostate cancer in different countries, and systematically review management options and efficacy of first-line systemic therapies for patients with prostate cancer previously treated with definitive radical prostatectomy or radiation therapy., Evidence Acquisition: We performed a systematic review of studies published from January 2010 to December 2021 in MEDLINE, EMBASE, or ClinicalTrials.gov according to Preferred Reporting Items for Systematic Reviews and Meta-analyses guidelines. Quality was assessed using the Grades of Recommendation, Assessment, Development and Evaluation methodology. The potential regional burdens of recurrent prostate cancer were estimated by analyzing various regional registry data., Evidence Synthesis: A total of 40 studies met the inclusion criteria and an additional landmark study published after the query was included in this review. Patients with metastatic recurrent disease derive benefit from the addition of androgen receptor signaling inhibitors to androgen deprivation therapy, while docetaxel should be reserved for patients with a high-volume metastatic burden by conventional imaging. Patients with biochemical-only recurrent disease benefit from continuous or intermittent androgen deprivation therapy if they possess high-risk features such as short prostate-specific antigen doubling time or high serum prostate-specific antigen. Current limitations to the published literature include no consideration of contemporary positron emission tomography imaging for evaluating metastatic recurrence or burden and few quality of life assessments., Conclusions: This systematic review summarizes the findings and recommendations for first-line systemic therapy for patients with recurrent prostate cancer following local therapy., Patient Summary: We performed a systematic evaluation and summary of all studies published within the past decade on the topic of medications used to treat prostate cancer after it has recurred following radiation therapy or surgery. This review can be used to inform guidelines for prostate cancer management., (Copyright © 2022 European Association of Urology. Published by Elsevier B.V. All rights reserved.)

There are more than 70 distinct sarcomas, and this diversity complicates the development of precision-based therapeutics for these cancers. Prospective comprehensive genomic profiling could overcome this challenge by providing insight into sarcomas' molecular drivers. Through targeted panel sequencing of 7494 sarcomas representing 44 histologies, we identify highly recurrent and type-specific alterations that aid in diagnosis and treatment decisions. Sequencing could lead to refinement or reassignment of 10.5% of diagnoses. Nearly one-third of patients (31.7%) harbor potentially actionable alterations, including a significant proportion (2.6%) with kinase gene rearrangements; 3.9% have a tumor mutational burden ≥10 mut/Mb. We describe low frequencies of microsatellite instability (<0.3%) and a high degree of genome-wide loss of heterozygosity (15%) across sarcomas, which are not readily explained by homologous recombination deficiency (observed in 2.5% of cases). In a clinically annotated subset of 118 patients, we validate actionable genetic events as therapeutic targets. Collectively, our findings reveal the genetic landscape of human sarcomas, which may inform future development of therapeutics and improve clinical outcomes for patients with these rare cancers., (© 2022. The Author(s).)

In castration-resistant prostate cancer (CRPC), the loss of androgen receptor (AR) dependence leads to clinically aggressive tumors with few therapeutic options. We used ATAC-seq (assay for transposase-accessible chromatin sequencing), RNA-seq, and DNA sequencing to investigate 22 organoids, six patient-derived xenografts, and 12 cell lines. We identified the well-characterized AR-dependent and neuroendocrine subtypes, as well as two AR-negative/low groups: a Wnt-dependent subtype, and a stem cell-like (SCL) subtype driven by activator protein-1 (AP-1) transcription factors. We used transcriptomic signatures to classify 366 patients, which showed that SCL is the second most common subtype of CRPC after AR-dependent. Our data suggest that AP-1 interacts with the YAP/TAZ and TEAD proteins to maintain subtype-specific chromatin accessibility and transcriptomic landscapes in this group. Together, this molecular classification reveals drug targets and can potentially guide therapeutic decisions.

AKT- a key molecular regulator of PI-3K signaling pathway, is somatically mutated in diverse solid cancer types, and aberrant AKT activation promotes altered cancer cell growth, survival, and metabolism 1-8 . The most common of AKT mutations (AKT1 E17K) sensitizes affected solid tumors to AKT inhibitor therapy 7,8 . However, the pathway dependence and inhibitor sensitivity of the long tail of potentially activating mutations in AKT is poorly understood, limiting our ability to act clinically in prospectively characterized cancer patients. Here we show, through population-scale driver mutation discovery combined with functional, biological, and therapeutic studies that some but not all missense mutations activate downstream AKT effector pathways in a growth factor-independent manner and sensitize tumor cells to diverse AKT inhibitors. A distinct class of small in-frame duplications paralogous across AKT isoforms induce structural changes different than those of activating missense mutations, leading to a greater degree of membrane affinity, AKT activation, and cell proliferation as well as pathway dependence and hyper-sensitivity to ATP-competitive, but not allosteric AKT inhibitors. Assessing these mutations clinically, we conducted a phase II clinical trial testing the AKT inhibitor capivasertib (AZD5363) in patients with solid tumors harboring AKT alterations (NCT03310541). Twelve patients were enrolled, out of which six harbored AKT1-3 non-E17K mutations. The median progression free survival (PFS) of capivasertib therapy was 84 days (95% CI 50-not reached) with an objective response rate of 25% (n = 3 of 12) and clinical benefit rate of 42% (n = 5 of 12). Collectively, our data indicate that the degree and mechanism of activation of oncogenic AKT mutants vary, thereby dictating allele-specific pharmacological sensitivities to AKT inhibition., (© 2022. The Author(s).)

Background: Inherited germline TP53 pathogenic and likely pathogenic variants (gTP53) cause autosomal dominant multicancer predisposition including Li-Fraumeni syndrome (LFS). However, there is no known association of prostate cancer with gTP53., Objective: To determine whether gTP53 predisposes to prostate cancer., Design, Setting, and Participants: This multi-institutional retrospective study characterizes prostate cancer incidence in a cohort of LFS males and gTP53 prevalence in a prostate cancer cohort., Outcome Measurements and Statistical Analysis: We evaluated the spectrum of gTP53 variants and clinical features associated with prostate cancer., Results and Limitations: We identified 31 prostate cancer cases among 163 adult LFS males, including 26 of 54 aged ≥50 yr. Among 117 LFS males without prostate cancer at the time of genetic testing, six were diagnosed with prostate cancer over a median (interquartile range [IQR]) of 3.0 (1.3-7.2) yr of follow-up, a 25-fold increased risk (95% confidence interval [CI] 9.2-55; p < 0.0001). We identified gTP53 in 38 of 6850 males (0.6%) in the prostate cancer cohort, a relative risk 9.1-fold higher than that of population controls (95% CI 6.2-14; p < 0.0001; gnomAD). We observed hotspots at the sites of attenuated variants not associated with classic LFS. Two-thirds of available gTP53 prostate tumors had somatic inactivation of the second TP53 allele. Among gTP53 prostate cancer cases in this study, the median age at diagnosis was 56 (IQR: 51-62) yr, 44% had Gleason ≥8 tumors, and 29% had advanced disease at diagnosis., Conclusions: Complementary analyses of prostate cancer incidence in LFS males and gTP53 prevalence in prostate cancer cohorts suggest that gTP53 predisposes to aggressive prostate cancer. Prostate cancer should be considered as part of LFS screening protocols and TP53 considered in germline prostate cancer susceptibility testing., Patient Summary: Inherited pathogenic variants in the TP53 gene are likely to predispose men to aggressive prostate cancer., (Copyright © 2021 The Author(s). Published by Elsevier B.V. All rights reserved.)

Purpose: The US Food and Drug Administration has recently granted accelerated approval of the poly(ADP-ribose) polymerase (PARP) inhibitor rucaparib as treatment for men with metastatic castration-resistant prostate cancer (mCRPC) associated with a deleterious germline or somatic BRCA1 or BRCA2 (BRCA) alteration. As the safety profile of this new addition to the mCRPC treatment landscape may be unfamiliar to clinicians and patients, we summarize the data from the literature and provide practical guidelines for the management of treatment-emergent adverse events (TEAEs) that may occur during rucaparib treatment., Materials and Methods: Safety data were identified from PubMed and congress publications of trials involving men with mCRPC treated with oral rucaparib monotherapy (600 mg twice daily). Management guidelines for TEAEs were developed based on trial protocols, prescribing information, oncology association guidance, and the authors' clinical experience., Results: In clinical trials of men with mCRPC who received rucaparib (n = 193), TEAEs observed were consistent with that of other PARP inhibitors. The most frequent any-grade TEAEs included gastrointestinal events, asthenia/fatigue, anemia, increased alanine/aspartate aminotransferase, rash, and thrombocytopenia; the most frequent grade ≥3 TEAE was anemia. The majority of TEAEs were self-limiting and did not require treatment modification or interruption. Here, we provide recommendations on management of the most common TEAEs reported with rucaparib as well as other TEAEs of interest., Conclusion: Rucaparib's recent approval for treatment of BRCA-mutant mCRPC is practice changing. Proper management of TEAEs will allow maximum treatment benefit for patients receiving rucaparib., Competing Interests: BW Labadie has nothing to disclose. DS Morris has served in a consulting/advisory role for and received research funding from Clovis Oncology, AstraZeneca, Astellas, Bayer, Dendreon, Merck, Janssen, and Pfizer. AH Bryce has received honoraria from Astellas and Bayer; personal fees from Merck and Castle Biosciences, outside the submitted work. R Given has served in a consulting or advisory role and/or on speakers bureaus for Janssen, Bayer, and Myovant and has received research funding from Clovis, Janssen, Bayer, and Merck. J Zhang has served in a consulting or advisory role and/or on speakers bureaus for Clovis Oncology, AstraZeneca, Bayer, Dendreon, Merck, Sanofi, and Seattle Genetics and received research funding from Astellas Pharma, AstraZeneca, and Bayer. W Abida has served in a consulting or advisory role for Clovis Oncology, Daiichi Sankyo, Janssen Pharmaceuticals, MORE Health, and ORIC Pharmaceuticals; has received financial support for travel and/or accommodation from Clovis Oncology and ORIC Pharmaceuticals; has received personal fees from Roche, Medscape, and Onclive, outside the submitted work; and his institution has received research funding from Clovis Oncology, AstraZeneca, and Zenith Epigenetics. He is funded by National Cancer Institute (NCI) Cancer Center Support Grant P30 CA 008748, NCI Prostate Specialized Program of Research Excellence (SPORE) grant P50 CA092629-16, Department of Defense Prostate Cancer Research Program grant W81XWH-17-1-0124, and a Prostate Cancer Foundation Young Investigator Award. S Chowdhury has served in a consulting or advisory role and/or on speakers bureaus for Clovis Oncology, Astellas, Bayer, BeiGene, Janssen, and Pfizer; received honoraria from GlaxoSmithKline; received financial support for travel and accommodation from Clovis Oncology and BeiGene: and holds stock in Curve.life; grants from Sanofi; personal fees from Huma, Remedy, Telix, Novartis, and Astra Zeneca, during the conduct of the study. A Patnaik has served in a consulting or advisory role for Exelixis, Janssen, and Jounce Therapeutics; has received honoraria from Clovis Oncology, Merck, Prime Inc., and Roche; and has received research funding from Clovis Oncology, Progenics, Bristol Myers Squibb, and GlaxoSmithKline; and has received clinical trial support from Laekna and AstraZeneca outside the submitted work., (© 2022 Labadie et al.)

Metastatic progression is the main cause of death in cancer patients, whereas the underlying genomic mechanisms driving metastasis remain largely unknown. Here, we assembled MSK-MET, a pan-cancer cohort of over 25,000 patients with metastatic diseases. By analyzing genomic and clinical data from this cohort, we identified associations between genomic alterations and patterns of metastatic dissemination across 50 tumor types. We found that chromosomal instability is strongly correlated with metastatic burden in some tumor types, including prostate adenocarcinoma, lung adenocarcinoma, and HR+/HER2+ breast ductal carcinoma, but not in others, including colorectal cancer and high-grade serous ovarian cancer, where copy-number alteration patterns may be established early in tumor development. We also identified somatic alterations associated with metastatic burden and specific target organs. Our data offer a valuable resource for the investigation of the biological basis for metastatic spread and highlight the complex role of chromosomal instability in cancer progression., Competing Interests: Declaration of interests S.C. receives consulting fees from Novartis, Lilly, and Sanofi and research funding from Daiichi-Sankyo and Paige.ai. J.J.H. receives consulting fees from Bristol Myers Squibb, Merck, Exelexis, Eisai, QED, Cytomx, Zymeworks, Adaptiimmune, and ImVax and research funding from Bristol Myers Squibb. C.A.I.-D. receives research funding from Bristol Myers Squibb. P. Razavi received consultation/Ad board/Honoraria from Novartis, Foundation Medicine, AstraZeneca, Epic Sciences, Inivata, Natera, and Tempus and institutional grant/funding from Grail, Illumina, Novartis, Epic Sciences, and ArcherDx. C.M.R. has consulted regarding oncology drug development with AbbVie, Amgen, Astra Zeneca, Epizyme, Genentech/Roche, Ipsen, Jazz, Lilly, and Syros and serves on the scientific advisory boards of Bridge Medicines, Earli, and Harpoon Therapeutics. D.Z. receives research funding from Astra Zeneca, Plexxikon, and Genentech and consulting fees from Merck, Synlogic Therapeutics, GSK, Bristol Myers Squibb, Genentech, Xencor, Memgen, Immunos, Agenus, Hookipa, Calidi, and Synthekine. B.W. has an ad hoc membership advisory board Repare Therapeutics. W.A. receives speaking honoraria from Roche, Medscape, Aptitude Health, and Clinical Education Alliance; consulting fees from Clovis Oncology, Janssen, ORIC pharmaceuticals, Daiichi Sankyo; and research funding from AstraZeneca, Zenith Epigenetics, Clovis Oncology, ORIC pharmaceuticals, and Epizyme. G.K.A.-A. receives research funding from Arcus, Agios, Astra Zeneca, Bayer, BioNtech, BMS, Celgene, Flatiron, Genentech/Roche, Genoscience, Incyte, Polaris, Puma, QED, Sillajen, and Yiviva and consulting fees from Adicet, Agios, Astra Zeneca, Alnylam, Autem, Bayer, Beigene, Berry Genomics, Cend, Celgene, CytomX, Eisai, Eli Lilly, Exelixis, Flatiron, Genentech/Roche, Genoscience, Helio, Incyte, Ipsen, Legend Biotech, Loxo, Merck, MINA, Nerviano, QED, Redhill, Rafael, Silenseed, Sillajen, Sobi, Surface Oncology, Therabionics, Twoxar, Vector, and Yiviva. E.M.O. receives research funding from Genentech/Roche, Celgene/BMS, BioNTech, BioAtla, AstraZeneca, Arcus, Elicio, Parker Institute, and AstraZeneca and consulting fees from Cytomx Therapeutics (DSMB), Rafael Therapeutics (DSMB), Sobi, Silenseed, Tyme, Seagen, Molecular Templates, Boehringer Ingelheim, BioNTech, Ipsen, Polaris, Merck, IDEAYA, Cend, AstraZeneca, Noxxon, BioSapien, Bayer (spouse), Genentech-Roche (spouse), Celgene-BMS (spouse), and Eisai (spouse). M.A.P. receive consulting fees from BMS, Merck, Array BioPharma, Novartis, Incyte, NewLink Genetics, Aduro, Eisai, and Pfizer; honoraria from BMS and Merck; research support from RGenix, Infinity, BMS, Merck, Array BioPharma, Novartis, and AstraZeneca. G.J.R. has institutional research funding from Mirait, Takeda, Merck, Roche, Novartis, and Pfizer. S.F.B. holds a patent related to some of the work described targeting CIN in advanced cancer. He owns equity in, receives compensation from, and serves as a consultant and the scientific advisory board and board of directors of Volastra Therapeutics Inc. A.N.S. has advisory board/personal fees from Bristol-Myers Squibb, Immunocore, and Castle Biosciences; research support from Bristol-Myers Squibb, Immunocore, Xcovery, Polaris, Novartis, Pfizer, and Checkmate Pharmaceuticals; and research funding from OBI-Pharma, GSK, Silenseed, BMS, and Lilly. R.Y. receives consulting fees from Array BioPharma/Pfizer, Mirati Therapeutics, and Natera and research funding from Pfizer and Boehringer Ingelheim. D.R.J. is member of the advisory council for Astra Zeneca and member of the Clinical Trial Steering Committee for Merck. D.M. reports disclosures from AstraZeneca, Johnson & Johnson, Boston Scientific, Bristol-Myers Squibb, and Merck. S.P.S. is shareholder and consultant for Canexia Health Inc. M.F.B receives consulting fees from Roche, Eli Lilly, and PetDx and research funding from Grail. D.B.S. has received consulted for and received honoraria from Pfizer, Lilly/Loxo Oncology, Vividion Therapeutics, Scorpion Therapetuics, and BridgeBio. B.N. is an employee of Loxo Oncology at Lilly., (Copyright © 2022 Elsevier Inc. All rights reserved.)

Purpose: Black men die from prostate cancer twice as often as White men, a disparity likely due to inherited genetics, modifiable cancer risk factors, and healthcare access. It is incompletely understood how and why tumor genomes differ by self-reported race and genetic ancestry., Experimental Design: Among 2,069 men with prostate cancer (1,841 self-reported White, 63 Asian, 165 Black) with access to clinical-grade sequencing at the same cancer center, prevalence of tumor and germline alterations was assessed in cancer driver genes reported to have different alteration prevalence by race., Results: Clinical characteristics such as prostate-specific antigen and age at diagnosis as well as cancer stage at sample procurement differed by self-reported race. However, most genomic differences persisted when adjusting for clinical characteristics. Tumors from Black men harbored fewer PTEN mutations and more AR alterations than those from White men. Tumors from Asian men had more FOXA1 mutations and more ZFHX3 alterations than White men. Despite fewer TP53 mutations, tumors from Black men had more aneuploidy, particularly chromosome arm 8q gains, an adverse prognostic factor. Genetic ancestry was associated with similar tumor alterations as self-reported race, but also with modifiable cancer risk factors. Community-level average income was associated with chr8q gains after adjusting for race and ancestry., Conclusions: Tumor genomics differed by race even after accounting for clinical characteristics. Equalizing access to care may not fully eliminate such differences. Therapies for alterations more common in racial minorities are needed. Tumor genomic differences should not be assumed to be entirely due to germline genetics., (©2021 American Association for Cancer Research.)

Purpose: The PARP inhibitor rucaparib is approved in the United States for patients with metastatic castration-resistant prostate cancer (mCRPC) and a deleterious germline and/or somatic BRCA1 or BRCA2 (BRCA) alteration. While sequencing of tumor tissue is considered the standard for identifying patients with BRCA alterations (BRCA + ), plasma profiling may provide a minimally invasive option to select patients for rucaparib treatment. Here, we report clinical efficacy in patients with BRCA + mCRPC identified through central plasma, central tissue, or local genomic testing and enrolled in TRITON2., Patients and Methods: Patients had progressed after next-generation androgen receptor-directed and taxane-based therapies for mCRPC and had BRCA alterations identified by central sequencing of plasma and/or tissue samples or local genomic testing. Concordance of plasma/tissue BRCA status and objective response rate and prostate-specific antigen (PSA) response rates were summarized., Results: TRITON2 enrolled 115 patients with BRCA + identified by central plasma ( n = 34), central tissue ( n = 37), or local ( n = 44) testing. Plasma/tissue concordance was determined in 38 patients with paired samples and was 47% in 19 patients with a somatic BRCA alteration. No statistically significant differences were observed between objective and PSA response rates to rucaparib across the 3 assay groups. Patients unable to provide tissue samples and tested solely by plasma assay responded at rates no different from patients identified as BRCA + by tissue testing., Conclusions: Plasma, tissue, and local testing of mCRPC patients can be used to identify men with BRCA + mCRPC who can benefit from treatment with the PARP inhibitor rucaparib., (©2021 American Association for Cancer Research.)

Purpose: Lineage plasticity in prostate cancer-most commonly exemplified by loss of androgen receptor (AR) signaling and a switch from a luminal to alternate differentiation program-is now recognized as a treatment resistance mechanism. Lineage plasticity is a spectrum, but neuroendocrine prostate cancer (NEPC) is the most virulent example. Currently, there are limited treatments for NEPC. Moreover, the incidence of treatment-emergent NEPC (t-NEPC) is increasing in the era of novel AR inhibitors. In contradistinction to de novo NEPC, t-NEPC tumors often express the AR, but AR's functional role in t-NEPC is unknown. Furthermore, targetable factors that promote t-NEPC lineage plasticity are also unclear., Experimental Design: Using an integrative systems biology approach, we investigated enzalutamide-resistant t-NEPC cell lines and their parental, enzalutamide-sensitive adenocarcinoma cell lines. The AR is still expressed in these t-NEPC cells, enabling us to determine the role of the AR and other key factors in regulating t-NEPC lineage plasticity., Results: AR inhibition accentuates lineage plasticity in t-NEPC cells-an effect not observed in parental, enzalutamide-sensitive adenocarcinoma cells. Induction of an AR-repressed, lineage plasticity program is dependent on activation of the transcription factor E2F1 in concert with the BET bromodomain chromatin reader BRD4. BET inhibition (BETi) blocks this E2F1/BRD4-regulated program and decreases growth of t-NEPC tumor models and a subset of t-NEPC patient tumors with high activity of this program in a BETi clinical trial., Conclusions: E2F1 and BRD4 are critical for activating an AR-repressed, t-NEPC lineage plasticity program. BETi is a promising approach to block this program., (©2021 The Authors; Published by the American Association for Cancer Research.)

Purpose: Tumor mutational profiling is increasingly performed in patients with advanced cancer. We determined the extent to which germline mutation profiling guides therapy selection in patients with advanced cancer., Methods: Patients with cancer undergoing tumor genomic profiling were prospectively consented for germline cancer predisposition gene analysis (2015-2019). In patients harboring germline likely pathogenic or pathogenic (LP/P) alterations, therapeutic actionability was classified using a precision oncology knowledge base. Patients with metastatic or recurrent cancer receiving germline genotype-directed therapy were determined., Results: Among 11,947 patients across > 50 malignancies, 17% (n = 2,037) harbored a germline LP/P variant. By oncology knowledge base classification, 9% (n = 1042) had an LP/P variant in a gene with therapeutic implications (4% level 1; 4% level 3B; < 1% level 4). BRCA1/2 variants accounted for 42% of therapeutically actionable findings, followed by CHEK2 (13%), ATM (12%), mismatch repair genes (11%), and PALB2 (5%). When limited to the 9,079 patients with metastatic or recurrent cancer, 8% (n = 710) harbored level 1 or 3B genetic findings and 3.2% (n = 289) received germline genotype-directed therapy. Germline genotype-directed therapy was received by 61% and 18% of metastatic cancer patients with level 1 and level 3B findings, respectively, and by 54% of BRCA1/2 , 75% of mismatch repair, 43% of PALB2 , 35% of RAD51C/D , 24% of BRIP1 , and 19% of ATM carriers. Of BRCA1/2 patients receiving a poly(ADP-ribose) polymerase inhibitor, 45% (84 of 188) had tumors other than breast or ovarian cancer, wherein the drug, at time of delivery, was delivered in an investigational setting., Conclusion: In a pan-cancer analysis, 8% of patients with advanced cancer harbored a germline variant with therapeutic actionability with 40% of these patients receiving germline genotype-directed treatment. Germline sequence analysis is additive to tumor sequence analysis for therapy selection and should be considered for all patients with advanced cancer., Competing Interests: Zsofia K. StadlerConsulting or Advisory Role: Allergan (I), Genentech/Roche (I), Regeneron (I), Optos (I), Adverum (I), Novartis (I), Regenxbio (I), Gyroscope (I), Neurogene (I) Debyani ChakravartyConsulting or Advisory Role: Medendi Medical Travel Christopher J. FongStock and Other Ownership Interests: Various biotech ETFsPatents, Royalties, Other Intellectual Property: Ultra-Wideband Radar System for Animals Patent September 11, 2018, Patent issuer and number US20150181840A1, Monitoring Treatment of Peripheral Artery Disease (PAD) using Diffuse Optical Imaging, Imaging interfaces for full finger and full hand optical tomography, Systems and methods for dynamic imaging of tissue using digital optical tomography. Karen CadooHonoraria: OncLiveConsulting or Advisory Role: GlaxoSmithKline/Tesaro, AstraZeneca, MSD, GlaxoSmithKline, MJH Life SciencesResearch Funding: AstraZeneca, Syndax, MSD Ying LiuResearch Funding: AstraZeneca, Tesaro/GSK Maria I. CarloConsulting or Advisory Role: PfizerOther Relationship: Prostate Cancer Foundation, Robert Wood Johnson Foundation Alicia LathamOther Relationship: Conquer Cancer Foundation Ritika KundraStock and Other Ownership Interests: Pfizer Carol AghajanianConsulting or Advisory Role: Mersana, Eisai, Roche, AbbVie, AstraZeneca/Merck, Roche/Genentech, Repare TherapeuticsResearch Funding: Genentech/Roche, AbbVie, Clovis Oncology, AstraZeneca Nadeem Abu-RustumHonoraria: Prime OncologyResearch Funding: Stryker/Novadaq, GrailTravel, Accommodations, Expenses: Prime Oncology Anna VargheseConsulting or Advisory Role: RocheResearch Funding: Lilly, Verastem, BioMed Valley Discoveries, Bristol Myers Squibb, Silenseed, IlluminaTravel, Accommodations, Expenses: Roche Eileen M. O'ReillyConsulting or Advisory Role: Merck, Agios, AstraZeneca, Bayer, BeiGene, Berry Genomics, Celgene, CytomX Therapeutics, Debiopharm Group, Eisai, Exelixis/Ipsen, Flatiron Health, Incyte, Janssen, LAM Therapeutics, Lilly, Loxo, Genentech/Roche, Minapharma, QED Therapeutics, RedHill Biopharma, Sillajen, SOBI, Yiviva, Autem Medical, Gilead Sciences, Ipsen, Silenseed, TheraBionic, twoXAR, Vector HealthResearch Funding: AstraZeneca/MedImmune, Acta Biologica, Bristol Myers Squibb, Celgene, Genentech, Halozyme, MabVax, Roche, Silenseed Michael MorrisConsulting or Advisory Role: Bayer, Endocyte, Advanced Accelerator Applications, ORIC Pharmaceuticals, Johnson & Johnson, Curium Pharma, AthenexResearch Funding: Bayer, Sanofi, Endocyte, Progenics, Corcept Therapeutics, Roche/Genentech, JanssenTravel, Accommodations, Expenses: Endocyte, Fujifilm Wassim AbidaHonoraria: CARET, Roche, Medscape, Aptitude HealthConsulting or Advisory Role: Clovis Oncology, Janssen, MORE Health, ORIC Pharmaceuticals, Daiichi SankyoResearch Funding: AstraZeneca, Zenith Epigenetics, Clovis Oncology, GlaxoSmithKline, ORIC Pharmaceuticals, EpizymeTravel, Accommodations, Expenses: GlaxoSmithKline, Clovis Oncology, ORIC Pharmaceuticals Alexander DrilonHonoraria: Medscape, OncLive, PeerVoice, Physicans' Education Resource, Targeted Oncology, MORE Health, Research to Practice, Foundation Medicine, PeerviewConsulting or Advisory Role: Ignyta, Loxo, TP Therapeutics, AstraZeneca, Pfizer, Blueprint Medicines, Genentech/Roche, Helsinn Therapeutics, BeiGene, Hengrui Therapeutics, Exelixis, Bayer, Tyra Biosciences, Verastem, Takeda/Millennium, BerGenBio, MORE Health, Lilly, Verastem, AbbVie, 14ner Oncology/Elevation Oncology, Remedica, Archer, Monopteros Therapeutics, Novartis, EMD Serono/Merck, Melendi, Repare TherapeuticsResearch Funding: Foundation MedicinePatents, Royalties, Other Intellectual Property: Wolters Kluwer (Royalties for Pocket Oncology)Other Relationship: Merck, GlaxoSmithKline, Teva, Taiho Pharmaceutical, Pfizer, PharmaMar, Puma Biotechnology Ahmet ZehirStock and Other Ownership Interests: Arcus Biosciences, Mirati TherapeuticsHonoraria: Illumina Marc LadanyiConsulting or Advisory Role: Bristol Myers Squibb, BayerResearch Funding: Loxo, Helsinn Therapeutics, Merus NV, Elevation Oncology David SolitStock and Other Ownership Interests: Loxo, Scorpion Therapeutics, Vividion Therapeutics, Fore TherapeuticsConsulting or Advisory Role: Pfizer, Illumina, Lilly, QED Therapeutics, BridgeBio Pharma, Scorpion Therapeutics, Vividion Therapeutics, Syros Pharmaceuticals Michael F. BergerResearch Funding: GrailPatents, Royalties, Other Intellectual Property: Provisional patent pending for “Systems and Methods for Detecting Cancer via cfDNA Screening” Luis A. DiazLeadership: Personal Genome Diagnostics, Jounce TherapeuticsStock and Other Ownership Interests: PapGene Inc, Personal Genome Diagnostics, Jounce Therapeutics, Zydecom, Thrive Earlier Detection Corp, Neophore, Amgen, Four Paws, Seer, Kinnate BiopharmaConsulting or Advisory Role: Merck, Personal Genome Diagnostics, Zydecom, Neophore, Innovatus Capital Partners, Four Paws, Seer, Kinnate BiopharmaResearch Funding: MerckPatents, Royalties, Other Intellectual Property: US-2010041048-A1—Circulating Mutant DNA to Assess Tumor Dynamics, US-2015344970-A1—Personalized Tumor Biomarkers, WO-2010118016-A2—Digital quantification of DNA methylation, US-2005202465-A1—Thymidylate synthase gene and metastasis, US-2014227271-A1—Somatic mutations in atrx in brain cancer, WO-2012094401-A2—Genes frequently altered in pancreatic neuroendocrine tumors, US-2013323167-A1—Detecting and treating solid tumors through selective disruption of tumor vasculature, EP-2912468-B1—Papanicolaou test for ovarian and endometrial cancers, US-9976184-B2—Mutations in pancreatic neoplasms, US-2017267760-A1—Checkpoint Blockade and Microsatellite Instability, US-2018171413-A1—Head and neck squamous cell carcinoma assays, US-2018086832-A1—HLA-restricted epitopes encoded by somatically mutated genes, US-2018258490-A1—Assaying ovarian cyst fluid, US-2016208340-A1—TERT Promoter Mutations in Urothelial Neoplasia, US-2015252415-A1—Arid1b and neuroblastoma, WO-2018071796-A2—Compositions and methods for identifying functional anti-tumor T cell responses, EP-3322824-A1—Detection of tumor-derived DNA in CSF, US-2016273049-A1—Systems and methods for analyzing nucleic acid, US-2018135044-A1—Non-unique barcodes in a genotyping assay, US-2017016075-A1—Neoantigen analysisTravel, Accommodations, Expenses: Merck Mark RobsonConsulting or Advisory Role: Change HealthCareResearch Funding: AstraZeneca, Pfizer, MerckOther Relationship: Research to Practice, Clinical Care Options, Physicans' Education Resource, Invitae, PfizerUncompensated Relationships: Merck, Pfizer, Daiichi Sankyo, Epic SciencesOpen Payments Link: https://openpaymentsdata.cms.gov/physician/612669/summaryNo other potential conflicts of interest were reported.

Circulating cell-free DNA from blood plasma of cancer patients can be used to non-invasively interrogate somatic tumor alterations. Here we develop MSK-ACCESS (Memorial Sloan Kettering - Analysis of Circulating cfDNA to Examine Somatic Status), an NGS assay for detection of very low frequency somatic alterations in 129 genes. Analytical validation demonstrated 92% sensitivity in de-novo mutation calling down to 0.5% allele frequency and 99% for a priori mutation profiling. To evaluate the performance of MSK-ACCESS, we report results from 681 prospective blood samples that underwent clinical analysis to guide patient management. Somatic alterations are detected in 73% of the samples, 56% of which have clinically actionable alterations. The utilization of matched normal sequencing allows retention of somatic alterations while removing over 10,000 germline and clonal hematopoiesis variants. Our experience illustrates the importance of analyzing matched normal samples when interpreting cfDNA results and highlights the importance of cfDNA as a genomic profiling source for cancer patients.

Purpose: Comprehensive genomic profiling (CGP) is of increasing value for patients with metastatic castration-resistant prostate cancer (mCRPC). mCRPC tends to metastasize to bone, making tissue biopsies challenging to obtain. We hypothesized CGP of cell-free circulating tumor DNA (ctDNA) could offer a minimally invasive alternative to detect targetable genomic alterations (GA) that inform clinical care., Experimental Design: Using plasma from 3,334 patients with mCRPC (including 1,674 screening samples from TRITON2/3), we evaluated the landscape of GAs detected in ctDNA and assessed concordance with tissue-based CGP., Results: A total of 3,129 patients (94%) had detectable ctDNA with a median ctDNA fraction of 7.5%; BRCA1/2 was mutated in 295 (8.8%). In concordance analysis, 72 of 837 patients had BRCA1/2 mutations detected in tissue, 67 (93%) of which were also identified using ctDNA, including 100% of predicted germline variants. ctDNA harbored some BRCA1/2 alterations not identified by tissue testing, and ctDNA was enriched in therapy resistance alterations, as well as possible clonal hematopoiesis mutations (e.g., in ATM and CHEK2 ). Potential androgen receptor resistance alterations were detected in 940 of 2,213 patients (42%), including amplifications, polyclonal and compound mutations, rearrangements, and novel deletions in exon 8., Conclusions: Genomic analysis of ctDNA from patients with mCRPC recapitulates the genomic landscape detected in tissue biopsies, with a high level of agreement in detection of BRCA1/2 mutations, but more acquired resistance alterations detected in ctDNA. CGP of ctDNA is a compelling clinical complement to tissue CGP, with reflex to tissue CGP if negative for actionable variants. See related commentary by Hawkey and Armstrong, p. 2961 ., (©2021 American Association for Cancer Research.)

Background: Cell-free DNA (cfDNA) profiling is increasingly used to guide cancer care, yet mutations are not always identified. The ability to detect somatic mutations in plasma depends on both assay sensitivity and the fraction of circulating DNA in plasma that is tumor-derived (i.e., cfDNA tumor fraction). We hypothesized that cfDNA tumor fraction could inform the interpretation of negative cfDNA results and guide the choice of subsequent assays of greater genomic breadth or depth., Methods: Plasma samples collected from 118 metastatic cancer patients were analyzed with cf-IMPACT, a modified version of the FDA-authorized MSK-IMPACT tumor test that can detect genomic alterations in 410 cancer-associated genes. Shallow whole genome sequencing (sWGS) was also performed in the same samples to estimate cfDNA tumor fraction based on genome-wide copy number alterations using z-score statistics. Plasma samples with no somatic alterations detected by cf-IMPACT were triaged based on sWGS-estimated tumor fraction for analysis with either a less comprehensive but more sensitive assay (MSK-ACCESS) or broader whole exome sequencing (WES)., Results: cfDNA profiling using cf-IMPACT identified somatic mutations in 55/76 (72%) patients for whom MSK-IMPACT tumor profiling data were available. A significantly higher concordance of mutational profiles and tumor mutational burden (TMB) was observed between plasma and tumor profiling for plasma samples with a high tumor fraction (z-score≥5). In the 42 patients from whom tumor data was not available, cf-IMPACT identified mutations in 16/42 (38%). In total, cf-IMPACT analysis of plasma revealed mutations in 71/118 (60%) patients, with clinically actionable alterations identified in 30 (25%), including therapeutic targets of FDA-approved drugs. Of the 47 samples without alterations detected and low tumor fraction (z-score<5), 29 had sufficient material to be re-analyzed using a less comprehensive but more sensitive assay, MSK-ACCESS, which revealed somatic mutations in 14/29 (48%). Conversely, 5 patients without alterations detected by cf-IMPACT and with high tumor fraction (z-score≥5) were analyzed by WES, which identified mutational signatures and alterations in potential oncogenic drivers not covered by the cf-IMPACT panel. Overall, we identified mutations in 90/118 (76%) patients in the entire cohort using the three complementary plasma profiling approaches., Conclusions: cfDNA tumor fraction can inform the interpretation of negative cfDNA results and guide the selection of subsequent sequencing platforms that are most likely to identify clinically-relevant genomic alterations.

Purpose: Alterations in DNA damage repair (DDR) pathway genes occur in 20%-25% of men with metastatic castration-resistant prostate cancer (mCRPC). Although PARP inhibitors (PARPis) have been shown to benefit men with mCRPC harboring DDR defects due to mutations in BRCA1/2 and ATM, additional treatments are necessary because the effects are not durable., Experimental Design: We performed transcriptomic analysis of publicly available mCRPC cases, comparing BRCA2 null with BRCA2 wild-type. We generated BRCA2 -null prostate cancer cells using CRISPR/Cas9 and treated these cells with PARPis and SRC inhibitors. We also assessed the antiproliferative effects of combination treatment in 3D prostate cancer organoids., Results: We observed significant enrichment of the SRC signaling pathway in BRCA2 -altered mCRPC. BRCA2 -null prostate cancer cell lines had increased SRC phosphorylation and higher sensitivity to SRC inhibitors (e.g., dasatinib, bosutinib, and saracatinib) relative to wild-type cells. Combination treatment with PARPis and SRC inhibitors was antiproliferative and had a synergistic effect in BRCA2 -null prostate cancer cells, mCRPC organoids, and Trp53/Rb1-null prostate cancer cells. Inhibition of SRC signaling by dasatinib augmented DNA damage in BRCA2 -null prostate cancer cells. Moreover, SRC knockdown increased PARPi sensitivity in BRCA2 -null prostate cancer cells., Conclusions: This work suggests that SRC activation may be a potential mechanism of PARPi resistance and that treatment with SRC inhibitors may overcome this resistance. Our preclinical study demonstrates that combining PARPis and SRC inhibitors may be a promising therapeutic strategy for patients with BRCA2 -null mCRPC., (©2020 American Association for Cancer Research.)

Purpose: BRCA1 or BRCA2 ( BRCA ) alterations are common in men with metastatic castration-resistant prostate cancer (mCRPC) and may confer sensitivity to poly(ADP-ribose) polymerase inhibitors. We present results from patients with mCRPC associated with a BRCA alteration treated with rucaparib 600 mg twice daily in the phase II TRITON2 study., Methods: We enrolled patients who progressed after one to two lines of next-generation androgen receptor-directed therapy and one taxane-based chemotherapy for mCRPC. Efficacy and safety populations included patients with a deleterious BRCA alteration who received ≥ 1 dose of rucaparib. Key efficacy end points were objective response rate (ORR; per RECIST/Prostate Cancer Clinical Trials Working Group 3 in patients with measurable disease as assessed by blinded, independent radiology review and by investigators) and locally assessed prostate-specific antigen (PSA) response (≥ 50% decrease from baseline) rate., Results: Efficacy and safety populations included 115 patients with a BRCA alteration with or without measurable disease. Confirmed ORRs per independent radiology review and investigator assessment were 43.5% (95% CI, 31.0% to 56.7%; 27 of 62 patients) and 50.8% (95% CI, 38.1% to 63.4%; 33 of 65 patients), respectively. The confirmed PSA response rate was 54.8% (95% CI, 45.2% to 64.1%; 63 of 115 patients). ORRs were similar for patients with a germline or somatic BRCA alteration and for patients with a BRCA1 or BRCA2 alteration, while a higher PSA response rate was observed in patients with a BRCA2 alteration. The most frequent grade ≥ 3 treatment-emergent adverse event was anemia (25.2%; 29 of 115 patients)., Conclusion: Rucaparib has antitumor activity in patients with mCRPC and a deleterious BRCA alteration, but with a manageable safety profile consistent with that reported in other solid tumor types.

Despite advances in prostate cancer screening and treatment, available therapy options, particularly in later stages of the disease, remain limited and the treatment-resistant setting represents a serious unmet medical need. Moreover, disease heterogeneity and disparities in patient access to medical advances result in significant variability in outcomes across patients. Disease classification based on genomic sequencing is a promising approach to identify patients whose tumors exhibit actionable targets and make more informed treatment decisions. Here we discuss how we can accelerate precision oncology to inform broader genomically-driven clinical decisions for men with advanced prostate cancer, drug development and ultimately contribute to new treatment paradigms., Competing Interests: Competing Interests Statement. J.M. reports advisory board participation for Amgen, AstraZeneca, Roche, Janssen, MSD and Clovis Oncology; research funding from AstraZeneca and Pfizer Oncology; W.A. reports consulting /advisory for Clovis, Janssen, More Health, ORIC, Daiichi Sankyo; research funding from AstraZeneca, Zenith Epigenetics, Clovis, GlaxoSmithKline, ORIC, Epizyme; travel from GlaxoSmithKline, Clovis, ORIC; and honoraria from CARET. R.R.M. received research funding from Bayer, Pfizer, Tempus; serves on Advisory Board for Bayer, Bristol Myers Squib, Exelixis, Janssen, Novartis, Pfizer, Sanofi, Tempus; is a consultant for Dendreon, Vividion. R.A. reports advisory board participation and research funding from Merck, AstraZeneca, and Janssen; B.M. reports research funding from AstraZeneca, Janssen, Clovis, Astellas, Beigene; M.R. reports consulting: Amgen, Ambryx, Constellation; educational writing and consulting: Plexus; speaking: Bayer, Janssen; funding and clinical research support: Novartis, Astellas, Medivation, Merck; D.B.S. has consulted for/received honoraria from Pfizer, Loxo Oncology, Lilly Oncology, BioBridge, Vivideon Therapeutics, and Illumina; E.V. reports advisory/consulting: Tango Therapeutics, Genome Medical, Invitae, Enara Bio, Janssen, Manifold Bio, Monte Rosa; research support: Novartis, BMS; Equity: Tango Therapeutics, Genome Medical, Syapse, Enara Bio, Manifold Bio, Microsoft, Monte Rosa; travel reimbursement: Roche/Genentech; institutional patents on chromatin mutations and immunotherapy response, and methods for clinical interpretation; D.V. reports honoraria from Clovis Oncology. H.B. reports advisory/consulting from Janssen, Amgen, Astra Zeneca, Pfizer, Astellas, Sanofi Genzyme and research funding from Janssen, Abbvie Stemcentryx, Eli Lilly, Millenium, Astellas. J.V. is employed by the Prostate Cancer Clinical Trials Consortium. H.R.S., J.W.S., and A.K.M. are employed by the Prostate Cancer Foundation.

Background: CDK12 genomic alterations occur in several tumor types, but little is known about their oncogenic role and clinical significance., Objective: To describe the landscape of CDK12 alterations across solid cancers and the clinical features of CDK12-altered prostate cancer., Design, Setting, and Participants: A single-center retrospective study of 26743 patients across 25 solid tumor types who underwent tumor sequencing was performed. Clinicopathologic features and outcomes were assessed in prostate cancer., Outcome Measurements and Statistical Analysis: CDK12 alterations and their association with genomic characteristics are described. For prostate cancer patients, overall survival and time to castration resistance were assessed using univariable and multivariable Cox regression analysis., Results and Limitations: CDK12 alterations were identified in 404/26743 patients (1.5%) overall, but were most frequent in prostate (100/1875, 5.3%) and ovarian cancer (43/1034, 4.2%), in which they were associated with a high prevalence of truncating variants and biallelic inactivation. CDK12 alterations defined a genomic subtype of prostate cancer with a unique copy-number alteration profile and involvement of distinct oncogenic pathway alterations, including cell-cycle pathway genes. CDK12-altered prostate cancer was associated with somewhat more aggressive clinical features and shorter overall survival (median 64.4 vs 74.9 mo; p=0.032) independent of standard clinical factors and tumor copy-number alteration burden (adjusted hazard ratio 1.80, 95% confidence interval 1.12-2.89; p=0.024). The study is limited by its retrospective nature., Conclusions: CDK12 alteration is a rare event across solid cancers but defines a clinically distinct molecular subtype of prostate cancer associated with unique genomic alterations and slightly more aggressive clinical features., Patient Summary: CDK12 gene alterations occur rarely across tumor types, but more frequently in prostate cancer, where they are associated with genomic instability, cell-cycle pathway gene alterations, and somewhat worse clinical outcomes, warranting further investigation of therapeutic targeting of this disease subset., (Copyright © 2020 European Association of Urology. Published by Elsevier B.V. All rights reserved.)

Purpose: ZEN-3694 is a bromodomain extraterminal inhibitor (BETi) with activity in androgen-signaling inhibitor (ASI)-resistant models. The safety and efficacy of ZEN-3694 plus enzalutamide was evaluated in a phase Ib/IIa study in metastatic castration-resistant prostate cancer (mCRPC)., Patients and Methods: Patients had progressive mCRPC with prior resistance to abiraterone and/or enzalutamide. 3+3 dose escalation was followed by dose expansion in parallel cohorts (ZEN-3694 at 48 and 96 mg orally once daily, respectively)., Results: Seventy-five patients were enrolled ( N = 26 and 14 in dose expansion at low- and high-dose ZEN-3694, respectively). Thirty (40.0%) patients were resistant to abiraterone, 34 (45.3%) to enzalutamide, and 11 (14.7%) to both. ZEN-3694 dosing ranged from 36 to 144 mg daily without reaching an MTD. Fourteen patients (18.7%) experienced grade ≥3 toxicities, including three patients with grade 3 thrombocytopenia (4%). An exposure-dependent decrease in whole-blood RNA expression of BETi targets was observed (up to fourfold mean difference at 4 hours post-ZEN-3694 dose; P ≤ 0.0001). The median radiographic progression-free survival (rPFS) was 9.0 months [95% confidence interval (CI), 4.6-12.9] and composite median radiographic or clinical progression-free survival (PFS) was 5.5 months (95% CI, 4.0-7.8). Median duration of treatment was 3.5 months (range, 0-34.7+). Lower androgen receptor (AR) transcriptional activity in baseline tumor biopsies was associated with longer rPFS (median rPFS 10.4 vs. 4.3 months)., Conclusions: ZEN-3694 plus enzalutamide demonstrated acceptable tolerability and potential efficacy in patients with ASI-resistant mCRPC. Further prospective study is warranted including in mCRPC harboring low AR transcriptional activity., (©2020 American Association for Cancer Research.)

Purpose: Metastatic castration-resistant prostate cancer (mCRPC) with low androgen receptor (AR) and without neuroendocrine signaling, termed double-negative prostate cancer (DNPC), is increasingly prevalent in patients treated with AR signaling inhibitors and is in need of new biomarkers and therapeutic targets., Methods: Candidate genes enriched in DNPC were determined using differential gene expression analysis of discovery and validation cohorts of mCRPC biopsies. Laboratory studies were carried out in human mCRPC organoid cultures, prostate cancer (PCa) cell lines, and mouse xenograft models. Epigenetic studies were carried out in a rapid autopsy cohort., Results: Dickkopf-1 (DKK1) expression is increased in DNPC relative to prostate-specific antigen (PSA)-expressing mCRPC in the Stand Up to Cancer/Prostate Cancer Foundation discovery cohort (11.2 v 0.28 reads per kilobase per million mapped reads; q < 0.05; n = 117) and in the University of Washington/Fred Hutchinson Cancer Research Center cohort (9.2 v 0.99 fragments per kilobase of transcript per million mapped reads; P < .0001). DKK1 expression can be regulated by activated Wnt signaling in vitro and correlates with activating canonical Wnt signaling mutations and low PSA mRNA in mCRPC biopsies ( P < .05). DKK1 hypomethylation was associated with increased DKK1 mRNA expression (Pearson r = -0.66; P < .0001) in a rapid autopsy cohort (n = 7). DKK1-high mCRPC biopsies are infiltrated with significantly higher numbers of quiescent natural killer (NK) cells ( P < .005) and lower numbers of activated NK cells ( P < .0005). Growth inhibition of the human PCa model PC3 by the anti-DKK1 monoclonal antibody DKN-01 depends on the presence of NK cells in a severe combined immunodeficient xenograft mouse model., Conclusion: These results support DKK1 as a contributor to the immunosuppressive tumor microenvironment of DNPC. These data have provided the rationale for a clinical trial targeting DKK1 in mCRPC (ClinicalTrials.gov identifier: NCT03837353)., Competing Interests: The following represents disclosure information provided by authors of this manuscript. All relationships are considered compensated unless otherwise noted. Relationships are self-held unless noted. I = Immediate Family Member, Inst = My Institution. Relationships may not relate to the subject matter of this manuscript. For more information about ASCO's conflict of interest policy, please refer to www.asco.org/rwc or ascopubs.org/po/author-center. Open Payments is a public database containing information reported by companies about payments made to US-licensed physicians (Open Payments). David R. WiseHonoraria: OncLive Consulting or Advisory Role: Best Doctors, Leap Therapeutics, GLG, Guidepoint Global, Pfizer, Foundation Medicine, Silverlight, Alphasights Travel, Accommodations, Expenses: PfizerJeffrey A. SchneiderStock and Other Ownership Interests: Abbott Laboratories, AstraZeneca, AbbVie, CVS Health, MerckBrigit McLaughlinEmployment: Bristol Myers Squibb Stock and Other Ownership Interests: Bristol Myers SquibbRyan BrennanEmployment: Flatiron Health Stock and Other Ownership Interests: RocheKatie L. ThorenResearch Funding: Sebia (Inst), The Binding Site (Inst)Wassim AbidaHonoraria: CARET Consulting or Advisory Role: Clovis Oncology, Janssen Pharmaceuticals, MORE Health, ORIC Pharmaceuticals, Daiichi Sankyo Research Funding: AstraZeneca (Inst), Zenith Epigenetics (Inst), Clovis Oncology (Inst), GlaxoSmithKline (Inst) Travel, Accommodations, Expenses: GlaxoSmithKline, Clovis Oncology, ORIC PharmaceuticalsAngelo M. De MarzoConsulting or Advisory Role: Cepheid Research Funding: Janssen Research & DevelopmentSrinivasan YegnasubramanianStock and Other Ownership Interests: Brahm Astra Therapeutics, Digital Harmonic Consulting or Advisory Role: Cepheid Research Funding: Cepheid (Inst), Celgene (Inst), Bristol Myers Squibb (Inst), Janssen Pharmaceuticals (Inst) Patents, Royalties, Other Intellectual Property: Patent: “COMPARE-MS: A novel technique for rapid, sensitive, and accurate detection of DNA methylation”; Patent: “Agents for reversing epigenetic silencing of genes”; Patent: “DNA methylation markers for metastatic prostate cancer”; Patent pending: “Induction of synthetic lethality with epigenetic therapy”; Patent: “Bisulfite-converted duplexes for the strand-specific detection and quantification of rare mutations”Michael HaasEmployment: Leap Therapeutics Stock and Other Ownership Interests: Leap Therapeutics Research Funding: Leap TherapeuticsMichael H. KageyEmployment: Leap Therapeutics, Biogen (I) Stock and Other Ownership Interests: Syros Pharmaceuticals Consulting or Advisory Role: Medical Research Commercialisation Fund Patents, Royalties, Other Intellectual Property: Patents pending and granted for discovery-based work at Leap Therapeutics (current employer), Tensha Therapeutics (acquired by Roche), and the Whitehead Institute (licensed to Syros Pharmaceuticals)Walter NewmanEmployment: Leap Therapeutics Leadership: Leap Therapeutics Stock and Other Ownership Interests: Leap Therapeutics Patents, Royalties, Other Intellectual Property: May be a co-patentee on Leap Therapeutics intellectual propertyCynthia A. SirardEmployment: Leap Therapeutics Leadership: Leap Therapeutics Stock and Other Ownership Interests: Leap Therapeutics Patents, Royalties, Other Intellectual Property: Pending patent application No. 62/260,959 Travel, Accommodations, Expenses: Leap TherapeuticsMichael J. MorrisConsulting or Advisory Role: Astellas Pharma, Bayer AG, Endocyte, Advanced Accelerator Applications, Blue Earth Diagnostics, Tokai Pharmaceuticals, Tolmar Pharmaceuticals, ORIC Pharmaceuticals Research Funding: Bayer AG (Inst), Sanofi (Inst), Endocyte (Inst), Progenics (Inst), Corcept Therapeutics (Inst), Roche (Inst), Genentech (Inst) Travel, Accommodations, Expenses: Bayer AG, EndocyteYu ChenStock and Other Ownership Interests: ORIC Pharmaceuticals Honoraria: Merck Patents, Royalties, Other Intellectual Property: Invention related to glucocorticoid inhibitors for treatment of prostate cancer (SK2013-045)Steven M. LarsonStock and Other Ownership Interests: Ymabs Therapeutics, Elucida Consulting or Advisory Role: Prescient Therapeutics Research Funding: Wilex, Regeneron Pharmaceuticals, Ymabs Therapeutics Patents, Royalties, Other Intellectual Property: Synthesis and utilization of 17-methyl and 17-cyclo-propylmethyl-3, 14-di-hydroxy-4, 5-epoxy 6 b-fluoromorphines (foxy and cyclofoxy) as (18F)-labeled opiate ligands for positron emission transaxial tomography (Rice KC, Pert CB, Burke TR Jr, Larson SM, Eckelman WC, Channing MA; October 4, 1988; US Patent No. 4,775,759); Antigen-specific composition and in vivo methods for detecting and localizing an antigenic site and for radiotherapy (Larson SM, Finn R, Carrasquillo JA, Reynolds JC, Neumann RD, Graham MC, Pentlow KS; February 9, 1993; US Patent No. 5,185,142); Non-invasive imaging and quantification of specific antigen and uses thereof (Smith-Jones P, Larson SM; January 6, 2003; Provisional Patent Application Registration No. 28,325); Single chain Fv polynucleotide or peptide construct of anti-ganglioside GD2 antibodies, cells expressing same and related methods (Cheung NK, Larson SM, Guo HF, Rivlin K, Sadelain M; US Patent No. 6,451,995); Small-molecule HSP90 inhibitors, chiosis, gabriela (Huazhong H, Llauger-Bufi L, Joungnam K, Larson S, Smith-Jones P; November 16, 2010, US Patent No. 7,834,181); Multi-specific antibodies with affinity for human A33 antigen and DOTA metal complex and uses thereof (Cheal S, Hong X, Larson SM, Cheung NK; February 9, 2015; US Patent No. 62,113,988); Systems and methods for determining optimum patient-specific antibody dose for tumor targeting (Zanzonico P, Cheal SM, Larson SM, Osborne J, Fung Edward K; May 22, 2015, US Patent No. 62,165699)Peter S. NelsonConsulting or Advisory Role: Janssen Oncology, Astellas Pharma, Roche, Genentech, Bristol Myers Squibb Research Funding: Genomic Health (Inst), Expert Testimony: Veneble-Fitzpatrick Law Firm Travel, Accommodations, Expenses: Janssen OncologyHoward I. ScherLeadership: Asterias Biotherapeutics Stock and Other Ownership Interests: Asterias Biotherapeutics Honoraria: Research to Practice Consulting or Advisory Role: Janssen Biotech, Amgen, Janssen Research & Development, Menarini Silicon Biosystems, WIRB-Copernicus Group, ESSA, Sanofi, Ambry Genetics, Konica Minolta, Pfizer, Bayer AG Research Funding: Janssen Pharmaceuticals (Inst), Illumina (Inst), Epic Sciences (Inst), Menarini Silicon Biosystems (Inst), Thermo Fisher Scientific (Inst) Travel, Accommodations, Expenses: Asterias Biotherapeutics, Menarini Silicon Biosystems, Amgen, WIRB-Copernicus Group, Konica Minolta, ESSA, Prostate Cancer Foundation, Sanofi, Bayer AG, Phosplatin TherapeuticsCharles L. SawyersLeadership: Novartis Stock and Other Ownership Interests: Novartis, Agios, Blueprint Medicines, BeiGene, ORIC Pharmaceuticals, Foghorn, PMV Pharma, KSQ Therapeutics, Petra Pharma Consulting or Advisory Role: Novartis, Blueprint Medicines, Agios, BeiGene, ORIC Pharmaceuticals, Foghorn, PMV Pharma, KSQ Therapeutics, Petra Pharma, Arsenal, Housey Pharmaceuticals Patents, Royalties, Other Intellectual Property: Xtandi, Apalutamide No other potential conflicts of interest were reported., (© 2020 by American Society of Clinical Oncology.)

Background: Molecular and immunohistochemistry-based profiling of prostatic adenocarcinoma has revealed frequent Androgen Receptor (AR) gene and protein alterations in metastatic disease. This includes an AR-null non-neuroendocrine phenotype of metastatic castrate resistant prostate cancer which may be less sensitive to androgen receptor signaling inhibitors. This AR-null non-neuroendocrine phenotype is thought to be associated with TP53 and RB1 alterations. Herein, we have correlated molecular profiling of metastatic castrate resistant prostate cancer with AR/P53/RB immunohistochemistry and relevant clinical correlates., Design: Twenty-seven cases of metastatic castrate resistant prostate cancer were evaluated using histopathologic examination to rule out neuroendocrine differentiation. A combination of a hybridization exon-capture next-generation sequencing-based assay (n = 26), fluorescence in situ hybridization for AR copy number status (n = 16), and immunohistochemistry for AR (n = 27), P53 (n = 24) and RB (n = 25) was used to profile these cases., Results: Of 27 metastatic castrate resistant prostate cancer cases, 17 had AR amplification and showed positive nuclear expression of AR by immunohistochemistry. Nine cases lacked AR copy number alterations using next-generation sequencing/fluorescence in situ hybridization. A subset of these metastatic castrate resistant prostate cancer cases demonstrated the AR-null phenotype by immunohistochemistry (five cases and one additional case where next-generation sequencing failed). Common co-alterations in these cases involved the TP53, RB1, and PTEN genes and all these patients received prior therapy with androgen receptor signaling inhibitors (abiraterone and/or enzalutamide)., Conclusions: Our study suggests that AR immunohistochemistry may distinguish AR-null from AR-expressing cases in the metastatic setting. AR-null status informs clinical decision-making regarding continuation of therapy with androgen receptor signaling inhibitors and consideration of other treatment options. This might be a relevant and cost-effective diagnostic strategy when there is limited access and/or limited tumor material for molecular testing.

Despite the development of second-generation antiandrogens, acquired resistance to hormone therapy remains a major challenge in treating advanced prostate cancer. We find that cancer-associated fibroblasts (CAFs) can promote antiandrogen resistance in mouse models and in prostate organoid cultures. We identify neuregulin 1 (NRG1) in CAF supernatant, which promotes resistance in tumor cells through activation of HER3. Pharmacological blockade of the NRG1/HER3 axis using clinical-grade blocking antibodies re-sensitizes tumors to hormone deprivation in vitro and in vivo. Furthermore, patients with castration-resistant prostate cancer with increased tumor NRG1 activity have an inferior response to second-generation antiandrogen therapy. This work reveals a paracrine mechanism of antiandrogen resistance in prostate cancer amenable to clinical testing using available targeted therapies., Competing Interests: Declaration of Interests C.L.S. and J.W. are co-inventors of enzalutamide and apalutamide and may be entitled to royalties. C.L.S. serves on the Board of Directors of Novartis and is a co-founder of ORIC Pharmaceuticals. He is a science advisor to Agios, Beigene, Blueprint, Column Group, Foghorn, Housey Pharma, Nextech, KSQ, Petra, and PMV. W.A. reports consulting for Clovis Oncology, Janssen, MORE Health, and ORIC Pharmaceuticals, and received honoraria from CARET and travel accommodations from GlaxoSmith Kline, Clovis Oncology, and ORIC Pharmaceuticals. D.E.R. reports having consulting or advisory role (uncompensated) from Genentech/Roche, Janssen Oncology, and TRACON Pharma, and received research funding from: AstraZeneca (Inst); Celgene (Inst); Ferring (Inst); Genentech/Roche (Inst); Janssen Oncology (Inst); Medivation/Astellas/Pfizer (Inst); Millennium (Inst); Novartis (Inst); Taiho Pharmaceutical (Inst); Takeda (Inst); TRACON Pharma (Inst). W.R.K. is a coinventor on patent WO2012168930A2 filed by Koninklijke Nederlandse Akademie Van Wetenschappen that covers organoid technology., (Copyright © 2020 The Authors. Published by Elsevier Inc. All rights reserved.)

To study genetic factors influencing the progression and therapeutic responses of advanced prostate cancer, we developed a fast and flexible system that introduces genetic alterations relevant to human disease directly into the prostate glands of mice using tissue electroporation. These electroporation-based genetically engineered mouse models (EPO-GEMM) recapitulate features of traditional germline models and, by modeling genetic factors linked to late-stage human disease, can produce tumors that are metastatic and castration-resistant. A subset of tumors with Trp53 alterations acquired spontaneous WNT pathway alterations, which are also associated with metastatic prostate cancer in humans. Using the EPO-GEMM approach and an orthogonal organoid-based model, we show that WNT pathway activation drives metastatic disease that is sensitive to pharmacologic WNT pathway inhibition. Thus, by leveraging EPO-GEMMs, we reveal a functional role for WNT signaling in driving prostate cancer metastasis and validate the WNT pathway as therapeutic target in metastatic prostate cancer. SIGNIFICANCE: Our understanding of the factors driving metastatic prostate cancer is limited by the paucity of models of late-stage disease. Here, we develop EPO-GEMMs of prostate cancer and use them to identify and validate the WNT pathway as an actionable driver of aggressive metastatic disease. This article is highlighted in the In This Issue feature, p. 890 ., (©2020 American Association for Cancer Research.)

Purpose: The genomic underpinning of clinical phenotypes and outcomes in metastatic castration-sensitive prostate cancer is unclear., Experimental Design: In patients with metastatic castration-sensitive prostate cancer at a tertiary referral center, clinical-grade targeted tumor sequencing was performed to quantify tumor DNA copy number alterations and alterations in predefined oncogenic signaling pathways. Disease volume was classified as high volume (≥4 bone metastases or visceral metastases) versus low volume., Results: Among 424 patients (88% white), 213 (50%) had high-volume disease and 211 (50%) had low-volume disease, 275 (65%) had de novo metastatic disease, and 149 (35%) had metastatic recurrence of nonmetastatic disease. Rates of castration resistance [adjusted hazard ratio, 1.84; 95% confidence interval (CI), 1.40-2.41] and death (adjusted hazard ratio, 3.71; 95% CI, 2.28-6.02) were higher in high-volume disease. Tumors from high-volume disease had more copy number alterations. The NOTCH, cell cycle, and epigenetic modifier pathways were the highest-ranking pathways enriched in high-volume disease. De novo metastatic disease differed from metastatic recurrences in the prevalence of CDK12 alterations but had similar prognosis. Rates of castration resistance differed 1.5-fold to 5-fold according to alterations in AR, SPOP (inverse), and TP53 , and the cell cycle, WNT (inverse), and MYC pathways, adjusting for disease volume and other genomic pathways. Overall survival rates differed 2-fold to 4-fold according to AR, SPOP (inverse), WNT (inverse), and cell-cycle alterations. PI3K pathway alterations were not associated with prognosis once adjusted for other factors., Conclusions: This study identified genomic features associated with prognosis in metastatic castration-sensitive disease that may aid in molecular classification and treatment selection., (©2020 American Association for Cancer Research.)

Purpose: Genomic alterations in DNA damage repair (DDR) genes other than BRCA may confer synthetic lethality with PARP inhibition in metastatic castration-resistant prostate cancer (mCRPC). To test this hypothesis, the phase II TRITON2 study of rucaparib included patients with mCRPC and deleterious non- BRCA DDR gene alterations., Patients and Methods: TRITON2 enrolled patients who had progressed on one or two lines of next-generation androgen receptor-directed therapy and one taxane-based chemotherapy for mCRPC. Key endpoints were investigator-assessed radiographic response per modified RECIST/PCWG3 and PSA response (≥50% decrease from baseline)., Results: TRITON2 enrolled 78 patients with a non- BRCA DDR gene alteration [ ATM ( n = 49), CDK12 ( n = 15), CHEK2 ( n = 12), and other DDR genes ( n = 14)]. Among patients evaluable for each endpoint, radiographic and PSA responses were observed in a limited number of patients with an alteration in ATM [2/19 (10.5%) and 2/49 (4.1%), respectively], CDK12 [0/10 (0%) and 1/15 (6.7%), respectively], or CHEK2 [1/9 (11.1%) and 2/12 (16.7%), respectively], including no radiographic or PSA responses in 11 patients with confirmed biallelic ATM loss or 11 patients with ATM germline mutations. Responses were observed in patients with alterations in the DDR genes PALB2, FANCA, BRIP1 , and RAD51B ., Conclusions: In this prospective, genomics-driven study of rucaparib in mCRPC, we found limited radiographic/PSA responses to PARP inhibition in men with alterations in ATM, CDK12 , or CHEK2 . However, patients with alterations in other DDR-associated genes (e.g., PALB2 ) may benefit from PARP inhibition. See related commentary by Sokolova et al., p. 2439 ., (©2020 American Association for Cancer Research.)

Androgen deprivation is the cornerstone of prostate cancer treatment. It results in involution of the normal gland to ~90% of its original size because of the loss of luminal cells. The prostate regenerates when androgen is restored, a process postulated to involve stem cells. Using single-cell RNA sequencing, we identified a rare luminal population in the mouse prostate that expresses stemlike genes ( Sca1 + and Psca + ) and a large population of differentiated cells ( Nkx3.1 + , Pbsn + ). In organoids and in mice, both populations contribute equally to prostate regeneration, partly through androgen-driven expression of growth factors (Nrg2, Rspo3) by mesenchymal cells acting in a paracrine fashion on luminal cells. Analysis of human prostate tissue revealed similar differentiated and stemlike luminal subpopulations that likewise acquire enhanced regenerative potential after androgen ablation. We propose that prostate regeneration is driven by nearly all persisting luminal cells, not just by rare stem cells., (Copyright © 2020 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.)