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TPS751 Background: Five doublet combinations incorporating immune checkpoint inhibitor (ICI) with or without tyrosine kinase inhibitor (TKI) are now approved for the first line treatment (tx) of advanced ccRCC. In COSMIC-313, the triplet combination with cabozantinib (CABO)-ipilimumab (IPI)-nivolumab (NIVO) demonstrated promising efficacy compared to IPI-NIVO in pts with intermediate/poor risk disease, but definitive overall survival (OS) benefit has yet to be shown, and is associated with higher incidence of adverse events. Currently, the optimal first /subsequent lines of therapies remain to be defined, and predictive biomarker to guide optimal tx approach is urgently needed. Pre-clinical studies allude to the ability of TKIs, such as CABO, to promote an immune-permissive environment and thus enhance ICI response. This open-label, single-arm, investigator-initiated pilot trial will evaluate the rapid sequencing from CABO to IPI-NIVO with the hypothesis of enhanced efficacy when compared to IPI-NIVO doublet, and potentially lower toxicity when compared to the concurrent triplet combination. Correlative studies, before and after administration of each systemic therapy, will be performed with the goal of identifying potential predictive biomarkers of response and resistance. Methods: Advanced, ccRCC pts will be treated with CABO 60mg PO once daily (QD) for 12 weeks (W) followed by IPI 1mg/kg + NIVO 3mg/kg IV every (Q)3W for 4 cycles. Subsequent therapy is dependent on response, and can be NIVO 480mg IV Q4W (CR/PR/SD), lenvatinib 18mg + everolimus 5mg PO QD (PD on both prior regimens), or re-initiation of CABO 60mg PO QD (CR/PR/SD at CABO but PD on IPI-NIVO). Key inclusion criteria are histologically confirmed, metastatic or unresectable RCC with predominantly clear cell component (sarcomatoid differentiation

135 Background: mCRPC is associated with (a/w) increased mortality among prostate cancer pts and new and safe txs are needed. In recent clinical trials, ARTs improved survival outcomes within this population, however, a significant portion will go on to discontinue tx. We aim to describe reasons for ART tx discontinuation and to identify predictors a/w increased risk of tx discontinuation due to tx toxicity or death. Methods: We performed a single-institution retrospective review of mCRPC pts on ART between 2010 and 2021. We screened for demographics, medical history, ART course, and tx side-effects. Our primary aim was to identify risk factors for tx discontinuation due to toxicity or death. Our secondary aim was to describe ART discontinuation among mCRPC. Fisher’s Exact was used to identify significant predictors of tx discontinuation due to toxicity or death. Significant outcomes were included in a multivariate logistic regression to determine odds ratios. Results: 133 pts with mCRPC started and discontinued ARTs. Among this cohort, 27 pts (20.3%) discontinued tx due to death or toxicity. Reasons for tx discontinuation are described in the table below. Significant predictors of tx discontinuation due to toxicity or death on bivariate analysis included pt-reported sepsis, hypertension (htn), weakness, falls, ECOG ≥2, and hospitalization during tx. Adjusting for confounders, pt-reported falls (OR 2.35; [0.91-2.59]; p=0.009), htn (OR 2.06; [0.94-2.21]; p=0.027), and weakness (OR 1.63; [0.59-2.72]; p=0.007) were a/w an increased risk of pt tx discontinuation from toxicity or death. Conclusions: Our results illustrate that the majority of mCRPC pts discontinued tx due to progression of disease. The data also indicates that mCRPC pts reporting new onset htn, falls, or weakness were more likely to discontinue tx due to toxicity or death. Early monitoring of this population is warranted to prolong duration of tx and prevent unnecessary txs. [Table: see text]

118 Background: mCRPC pts with significant comorbidities or poor performance status (PS) are often excluded from clinical trials for ART. These cohorts may not be representative of or comparable to real-world pts. We aimed to determine whether (1) baseline characteristics or (2) survival outcomes differed in pts with mCRPC categorized as eligible or ineligible for ART clinical trials. Methods: We screened for pts with mCRPC treated with abiraterone (abi-) or enzalutamide (enza-) at our institution between 2010 and 2021. Baseline characteristics were reviewed at treatment start and ART course recorded. We applied the inclusion/exclusion criteria from clinical trials, COU-AA-301, COU-AA-302, PREVAIL, and AFFIRM, to categorize pts as ineligible or eligible. Fischer’s exact was used to evaluate pt characteristics. Cox proportional hazards model was used to compare survival outcomes. Results: We identified 150 pts with mCRPC who initiated abi- or enza-. 54.7% of pts were deemed trial ineligible. Among pts on abi-, 48 of 86 (55.8%) pts were ineligible. Among those on enza-, 34 of 64 (53.1%) were ineligible. Common reasons for ineligibility included poor PS, radiation during treatment, and trial specific comorbidities. Among ineligible pts, 11% were post-chemotherapy compared to 20.6% of eligible pts (p = .162). Notably, trial ineligible pts were more likely to be non-Hispanic black when compared to trial eligible pts (29.3% vs. 17.6%, p = 0.036). Median OS was 30.2 for ineligible pts and 37.1 for eligible pts p = 0.46). for the ineligible pts and eligible pts respectively and there was no significant difference on univariate or multivariate analyses (HR: 0.84 [0.54, 1.32;]. Conclusions: Pts classified as trial ineligible had comparable survival outcomes when compared to trial eligible pts. Consistent with prior research on systemic racism in clinical trials, ineligible pts were more likely to identify as Black compared to eligible pts. Further research is warranted to confirm safety of ART in ineligible pts and identify strategies for reducing racial disparity gaps in cancer clinical trials.

194 Background: Statins may reinforce and provide a compounded effect on ART by decreasing cholesterol levels thus decreasing de novo androgen synthesis. We aim to investigate the clinical effect of concurrent statin and ART use on outcomes of mCRPC patients. Methods: We conducted a retrospective analysis on mCRPC patients receiving ART from a single institution. Relevant demographic and clinical data was collected in addition to ART treatment course, statin treatment, and survival outcomes. Our primary outcome was PSA progression free survival (PFS) and our secondary outcomes were overall survival (OS) and associated prognostic factors for both PSA PFS and OS. Chi-squared test and Wilcoxon signed ranked test were used to compare baseline characteristics, and a Cox proportional hazards regression model was used to estimate hazard ratios (HR) with 95% confidence interval (CI) for overall survival (OS) and PSA PFS. Results: 153 patients were included in the analysis between 2010 and 2021. 67 patients (mean age 73.8 years) received concurrent statins and 86 patients (mean age 67.6 years) did not. Median PSA PFS was 37.4 months for patients that received concurrent statins and 17.4 months for patients that did not receive statins. On univariate and multivariate analyses, there was no statistically significance difference between groups for PSA PFS (HR 0.7; CI 0.44-1.1; p=0.122). Median OS was 35.6 months for patients that received concurrent statins and 24.0 months for patients who did not. There was no statistical significance between groups for OS on univariate or multivariate analyses (HR 0.67; CI 0.42-1.06; p=0.087). Conclusions: Although results were not statistically significant, our study illustrates that concurrent statin use exhibits improved time to PSA progression and OS in mCRPC patients. Larger multi-center and further prospective studies are warranted to elucidate the relationship between statin use and overall outcomes in this population.

4532 Background: Multiple regimens incorporating tyrosine kinase inhibitors (TKI) or immune checkpoint inhibitors (ICI), either alone or in combination, confer a significant OS benefit in 1L metastatic clear cell RCC. However, guidance for optimal treatment selection in elderly patients remains limited. A network meta-analysis (NMA) was performed to compare the efficacy of 1L treatments for elderly patients with aRCC. Methods: Database search was performed through Pubmed, Embase, Web of Science, and Scopus. Eligible studies were randomized controlled trials (RCTs) evaluating first-line regimens for patients with aRCC older than 65 years old. The primary outcomes were progression-free survival (PFS) and overall survival (OS). Indirect comparisons of available regimens were estimated using a random-effects NMA. Results: 14 RCTs with more than 2,100 patients and 5 RCTs with 1,529 patients were eligible for PFS and OS analyses, respectively. Compared with sunitinib (Sun), the pembrolizumab (Pem) + axitinib (Axi) (HR 0.68, 95% CI 0.48-0.97) and Pem + lenvatinib (Len) (HR 0.61, 95% CI 0.4-0.94) regimens were associated with significantly improved OS. In comparing the TKI-ICI combinations with dual ICI nivolumab (Niv) + ipilimumab (Ipi), no significant OS differences were observed (Pem + Len: HR 0.71, 95% CI 0.40-1.27; Pem + Axi: HR 0.79, 95% CI 0.47-1.34; Avelumab (Ave) + Axi: HR 1.03, 95% CI 0.58-1.85; Niv + cabozantinib [Cab]: HR 1.03, 95% CI 0.57-1.93, using Niv + Ipi as a reference). Pem + Len, Niv + Cab, Pem + Axi, and Cab alone each showed improved PFS over Sun (Table). Among these, Pem + Len showed a PFS advantage compared to Pem + Axi (HR 0.58, 95% CI 0.37-0.91), but no PFS difference compared with the other regimens (vs Niv + Cab: HR 0.63, 95% CI 0.39-1.03; vs Cab alone: HR 0.84, 95% CI 0.40-1.77). Conclusions: Pem + Len and Pem + Axi provided the largest OS benefit in elderly patients for 1L aRCC. Pem + Len showed improved PFS compared with Pem + Axi, but no difference compared with Niv + Cab or Cab alone. Further validation using real-world data is needed to confirm the efficacy and safety of first-line regimens for the geriatric population with aRCC.[Table: see text]

Background Cell entry of SARS-CoV-2 depends on binding of the viral spike (S) proteins to ACE2 and on S protein priming by TMPRSS2. Inhibition of TMPRSS2 may work to block or decrease the severity of SARS-CoV-2 infections. Intriguingly, TMPRSS2 is an androgen-regulated gene that is upregulated in prostate cancer where it supports tumor progression and is involved in a frequent genetic translocation with the ERG gene. First- or second-generation androgen-deprivation therapies (ADTs) decrease the levels of TMPRSS2. Here we put forward the hypothesis that ADTs may protect patients affected by prostate cancer from SARS-CoV-2 infections. Materials and methods We extracted data regarding 9280 patients (4532 males) with laboratory-confirmed SARS-CoV-2 infection from 68 hospitals in Veneto, one of the Italian regions that was most affected by the COVID-19 pandemic. The parameters used for each COVID-19 positive patient were gender, hospitalization, admission to intensive care unit (ICU), death, tumor diagnosis, prostate cancer diagnosis, and androgen-deprivation therapy (ADT). Results There were 9280 SARS-CoV-2 positive patients in the Veneto on April 1, 2020. Overall, males developed more severe complications, were more frequently hospitalized, and had a worse clinical outcome than females. Considering only the Veneto male population (2.4 Million men), 0.2% and 0.3% of non-cancer and cancer patients, respectively, tested positive for SARS-CoV-2. Comparing the total number of SARS-CoV-2 positive cases, prostate cancer patients receiving ADT had a significantly lower risk of SARS-CoV-2 infection compared to patients who did not receive ADT (OR 4.05; 95% CI 1.55-10.59). A greater difference was found comparing prostate cancer patients receiving ADT to patients with any other type of cancer (OR 5.17; 95% CI 2.02-13.40). Conclusion Our data suggest that cancer patients have an increased risk of SARS-CoV-2 infections than non-cancer patients. However, prostate cancer patients receiving ADT appear to be partially protected from SARS-CoV-2 infections., HIGHLIGHTS • SARS-CoV-2 infected men have a worse clinical outcome than women • Cancer patients have an increased risk of SARS-CoV-2 infection • Prostate cancer patients receiving androgen-deprivation therapies appear to be partially protected from the infection

112 Background: Next-generation sequencing (NGS) is increasingly common in clinical practice, but its clinical utility may depend on the availability of sequencing-directed therapies (SDT). There were no FDA-approved SDTs in prostate cancer (PCa) until 2020, when PARP inhibitors olaparib and rucaparib were approved for tumors bearing alterations in certain homologous recombination repair (HRR) genes. We assessed the clinical utility of NGS in PCa before and after the approval of these agents in a single academic medical center. Methods: This was a retrospective single-center study including all PCa patients seen at Mount Sinai Hospital (New York, NY) between 2018–2021 who received NGS via the 161-gene Sema4 Signal Solid Tumor Panel. Clinical data were extracted from the Mount Sinai electronic medical record using a proprietary automated pipeline with limited manual curation (Sema4 PRODB). The primary outcome was clinical utility in metastatic PCa, defined as the proportion of metastatic PCa patients who received SDT. Secondary outcomes included time-to-next-treatment (TTNT, defined as time from SDT start to the start of next systemic therapy) and the proportion of patients with clinically actionable (as of 9/2021) alterations, defined as either Tier 1 (associated with FDA-approved treatments in prostate cancer) or Tier 2 (associated with either off-label or investigational agents). Results: The cohort consisted of 332 PCa patients; 51% (N = 170) were sequenced in 2020 or later. The median age at diagnosis was 65 (IQR 12). The most advanced stage documented was localized for 39% (N = 129) and metastatic for 61% (N = 203). Overall, 167 actionable alterations were identified in 125 patients (38% of cohort). Of the actionable alterations, 31% (N = 51) were Tier 1 and 69% (N = 116) were Tier 2. Of the 44 patients with Tier 1 alterations, 8 (18%) received SDT (all received olaparib). The proportion of metastatic patients receiving olaparib increased from 1% (2/145) before 2020 to 10% (6/58) during or after 2020 (p = 0.008). Of the 36 patients not receiving olaparib: 20 were sequenced before FDA approval and were treated with an alternative systemic therapy; 8 had localized disease and were not eligible; 8 had limited follow-up or unknown treatment status. For those who received olaparib, median TTNT was 5 months. Conclusions: In this single-center retrospective cohort, clinical utility of NGS was linked to treatment landscape. Increases in NGS test volume and olaparib use coincided with the approval of PARP inhibitors for patients with HRR-mutated prostate cancers. Notably, NGS was used to match patients to off-label/ investigational olaparib before its FDA approval.[Table: see text]

e17047 Background: The addition of docetaxel or a novel hormonal agent (NHA), such as abiraterone acetate or enzalutamide, has become standard of care for mHSPC, but prospective data for comparative efficacy remains limited. Clinical variables abstracted through natural language processing of free text from patient charts can provide real-world data to answer important clinical questions. Methods: Using an innovative data abstraction process, we retrospectively identified men with de novo mHSPC within deidentified charts from the Mount Sinai Health System treated with either docetaxel or a NHA between January 1, 2014 and April 30, 2019. Dates were chosen to reflect the timeline for which these therapeutic agents received regulatory approval for mHSPC, but also to allow sufficient clinical follow up after treatment initiation. Primary outcome of failure-free survival (FFS), defined as the time to next treatment, was assessed using the Kaplan-Meier method and multivariable Cox proportional hazards models. We additionally performed multivariable analysis to evaluate the prognostic significance of post-treatment PSA nadir on FFS. Results: A total of 94 de novo mHSPC patients that received either docetaxel or an NHA were identified using proprietary Sema4 data abstraction process: 52 received docetaxel, 42 received an NHA. Use of an upfront NHA in mHSPC was associated with a significantly longer FFS compared to docetaxel (20.7 vs. 10.1 months, p = 0.023). While NHAs were associated with a significantly longer FFS than docetaxel in patients with high metastatic burden of disease (25.12 vs. 9.63 months, p = 0.014), this was not observed in low-volume disease (20.71 vs. 26.5 months, p = 0.9). In multivariable model analysis adjusting for age, baseline PSA, and metastasis burden, docetaxel remains independently associated with worse FFS compared to NHA (HR 1.96, 95% CI 1.12−3.45, p = 0.019). Irrespective of docetaxel or NHA use, lower post-treatment PSA nadir levels were associated with improved FFS (58.95 vs. 11.57 vs. 9.4 months for PSA ≤0.2, 0.2-0.4, > 0.4ng/ml, respectively; p < 0.001). Conclusions: Clinical variables abstracted from deidentified clinical documentation can efficiently provide relevant and reliable data upon which clinical research can be based. Comparative analysis of real-world data demonstrates superior FFS in de novo mHSPC treated with a NHA as compared to docetaxel. The depth of PSA response holds prognostic value for mHSPC outcomes, regardless of treatment used.

41 Background: TMPRSS2, a cell surface protease which is commonly upregulated in prostate cancer (PC) and regulated by androgens, is a necessary component for SARS-CoV2 cellular entry into respiratory epithelial cells. PC patients receiving ADT were reported to have a lower risk of SARS-CoV-2 infection. However, whether ADT may have an impact on the severity of COVID-19 illness in this population is poorly understood. Methods: In this study performed across 7 US medical centers, we retrospectively evaluated patients with active PC and SARS-COV-2 viral detection by PCR between 03/01/20 and 05/31/20. We collected information on demographics; medical comorbidities; medications; PC Gleason score at initial diagnosis; presence of active disease, metastases, and castration resistance; ADT use as defined by GnRH analog or antagonist within 3 months or castration levels of testosterone < 50 ng/dL within 6 months of COVID-19 diagnosis, or history of bilateral orchiectomy; active non-ADT systemic therapies including, but not limited to, androgen-receptor-targeted therapies and chemotherapy; and COVID-19-related outcomes including hospitalization, supplemental oxygen use, mechanical ventilation requirement, WHO COVID-19 ordinal scale for clinical improvement, follow-up duration, and vital status. Multivariable mixed-effect logistic regression was performed to evaluate any difference in COVID-19 clinical outcomes between patients on and not on ADT. Survival analysis was done using adjusted Cox proportion-hazards regression model. All tests were two-sided at 0.05 significance level. Results: We identified 465 evaluable patients with median age of 71 (61-81) years. Median duration of follow-up was 60 (12-114.2) days. In this follow up period, there were 195 (41.9%) hospitalizations and 111 (23.9%) deaths. When adjusted for age, BMI, and PC clinical disease state, overall survival (HR 1.28 [95%CI 0.79-2.08], P = 0.32), hospitalization status (HR 1.07 [0.61-1.87], P = 0.82), supplemental oxygen use (HR 1.29 [0.77-2.17], P = 0.34), and use of mechanical ventilation (HR 1.07 [0.51-2.23], P = 0.87) were not statistically different between ADT and non-ADT cohorts. Similarly, in subgroup analysis, no statistical difference in overall survival was found between ADT and non-ADT cohorts for hospitalized patients (HR 1.42 [0.82-2.47], P = 0.21) and those receiving supplemental oxygen (HR 1.10 [0.65-1.85], P = 0.73). Conclusions: In this retrospective cohort of PC patients, use of ADT prior to COVID-19 diagnosis does not protect against severe COVID-19 illness as defined by hospitalization, supplemental oxygen use, or death. Further preclinical work in understanding TMPRSS2 expression and androgen regulation in respiratory epithelial cells is needed. As well, longer clinical follow-up and additional clinical studies inclusive of prospective data are warranted to fully address this question.

The increasing potency of therapies that target the androgen receptor (AR) signalling axis has correlated with a rise in the proportion of patients with prostate cancer harbouring an adaptive phenotype, termed treatment-induced lineage crisis. This phenotype is characterized by features that include soft-tissue metastasis and/or resistance to standard anticancer therapies. Potent anticancer treatments might force cancer cells to evolve and develop alternative cell lineages that are resistant to primary therapies, a mechanism similar to the generation of multidrug- resistant microorganisms after continued antibiotic use. Herein, we assess the hypothesis that treatment-adapted phenotypes harbour reduced AR expression and/or activity, and acquire compensatory strategies for cell survival. We highlight the striking similarities between castration-resistant prostate cancer and triple-negative breast cancer, another poorly differentiated endocrine malignancy. Alternative treatment paradigms are needed to avoid therapy-induced resistance. Herein, we present a new clinical trial strategy designed to evaluate the potential of rapid drug cycling as an approach to delay the onset of resistance and treatment-induced lineage crisis in patients with metastatic castration-resistant prostate cancer.

e17575 Background: Optimal sequencing of therapeutic agents in mCRPC remains debated, but the standard approach is to treat with one agent until resistance is met before switching. PRINT explores the efficacy of treating mCRPC with a rapidly-cycling, non-cross reactive regimen as a way to more effectively treat intrinsic heterogeneity, delay or prevent drug resistance, and minimize treatment toxicity. Methods: Patients received treatment with 3 consecutive treatment modules, each lasting 12 weeks: 1. abiraterone acetate 1000 mg PO daily + prednisone 5 mg PO BID; 2. cabazitaxel 20 mg/m2 IV + carboplatin AUC 4 IV q3 weeks; 3. enzalutamide 160 mg PO daily + radium-223 50 kBq/kg IV q4 weeks (in those with bone metastases). Upon completion of the 9-month regimen, patients are followed on ADT alone. Primary endpoint for the study is PSA or radiographic time to progression (TTP). Results: From 3/2017 to 1/2020, 38 of 40 planned men with mCRPC were enrolled, 28 patients have completed the 9-month study regimen and evaluable for TTP analysis. With median follow up of 54+ weeks, median time to PSA progression after therapy completion is 14.7+ weeks (95%CI; 5.5-23.9+ weeks). PSA response rates showed successive improvements with each sequential treatment module (Table). Eight patients (21.1%) continue on post-study surveillance with ADT alone, two of which have remained off any mCRPC agents for over a year (82+ weeks, 79+ weeks). In patients needing to restart therapy, experience with efficacy and tolerability of each agent while on the study, has helped inform subsequent mCRPC drug selection. The study regimen is well-tolerated, with few grade 3/4 AE’s: hyperglycemia (15.8%), diarrhea (5.3%), anemia (2.6%), fatigue (2.6%), neutropenia (2.6%), and thrombocytopenia (2.6%). Conclusions: Treatment of mCRPC with a rapidly-cycling non-cross reactive regimen demonstrates significant antitumor benefits, with potential for long-term suppression of disease. Further longitudinal follow up will determine if PRINT delays progression compared with standard approaches. Clinical trial information: NCT02903160 . [Table: see text]

89 Background: Optimal sequencing of therapeutic agents in mCRPC remains debated, but the standard approach is to treat with one agent until resistance is met before switching. PRINT explores the efficacy of treating mCRPC with a rapidly-cycling, non-cross reactive regimen as a way to more effectively treat intrinsic heterogeneity, delay/prevent drug resistance, and minimize toxicity. Methods: Enrolled patients all received 3 consecutive treatment modules, each 12 weeks: 1. abiraterone acetate 1000 mg PO daily + prednisone 5 mg PO BID; 2. cabazitaxel 20 mg/m2 IV + carboplatin AUC 4 IV q3 weeks; 3. enzalutamide 160 mg PO daily + radium-223 55 kBq/kg IV q4 weeks (in those with bone metastases). Upon completion of the 9-month regimen, patients are followed on ADT alone. Primary endpoint for the study is PSA or radiographic time to progression (TTP). Results: From 3/2017 to 10/2019, 35 of 40 planned men with mCRPC were enrolled, 25 patients have completed the 9-month study regimen and evaluable for TTP analysis. With median follow up of 52 weeks, median time to PSA progression after therapy completion is 15.5 weeks (95%CI; 5-26.1+ weeks). PSA response rates show successive improvements with each sequential treatment module (Table). Six (24%) patients continue on post-study surveillance with ADT alone, two of which have remained off any mCRPC agents for over a year (64+ weeks, 54+ weeks). In patients needing to restart therapy, experience with efficacy and tolerability of each agent while on the study, has helped inform subsequent mCRPC drug selection. The study regimen is well-tolerated, with few grade 3/4 AE’s: hyperglycemia (14.3%), diarrhea (5.7%), anemia (2.9%), fatigue (2.9%), neutropenia (2.9%), and thrombocytopenia (2.9%). Conclusions: Treatment of mCRPC with a rapidly-cycling non-cross reactive regimen demonstrates significant antitumor benefits, with potential for long-term suppression of disease. Further longitudinal follow up will determine if PRINT delays progression compared with standard approaches. Clinical trial information: NCT02903160. [Table: see text]

Advances in therapies have led to the approval of six therapeutic agents since 2004, each demonstrating overall survival benefit in randomized studies, and these have significantly improved the outlook for men facing metastatic castration-resistant prostate cancer (CRPC). More recently, efforts have been directed at trying to effect change at earlier phases of the disease. Apalutamide (ARN-509), a second-generation androgen receptor antagonist, recently received approval in the nonmetastatic (M0) CRPC space. Similar to enzalutamide, apalutamide inhibits the binding of androgen to androgen receptor (AR), nuclear translocation of the androgen-AR complex, and binding of AR transcription complex to DNA-binding sites and transcription elements. Phase I and II trial experience demonstrates the safety and tolerability of apalutamide, as well as its efficacy in effecting prostate-specific antigen response and radiographic-free survival in CRPC. US Food and Drug Administration approval in M0 CRPC was granted following positive results from the phase III SPARTAN study, where apalutamide demonstrated significant improvements in metastasis-free survival and time to symptomatic progression as compared to placebo.

Non-clear cell renal cell carcinoma (RCC) encompasses a diverse group of diseases, with research yielding different histologic findings and genetic profiles with each distinct subgroup. Simply mirroring the management techniques of clear cell RCC and borrowing from its growing armamentarium of therapeutic agents, while somewhat productive at first, but will ultimately be limiting. Further investigation into the molecular pathogenesis of disease, similarities and differences between specific subtypes, and mechanisms of resistance to therapeutics will help identify new targets, stimulate development of novel agents, and improve clinical trial offerings for non-clear cell RCC (nccRCC). As nccRCC has been largely excluded from past trials, there will be a need for future trials to be designed either to evaluate nccRCC specifically, or to include nccRCC as a prespecified subgroup. Multi-center collaborative trials should be supported, as many of the nccRCC subtypes are rare and remain underrepresented even within the construct of trials that only enroll nccRCC. Given the absence of clear molecular targets at present, patients with metastatic nccRCC should be offered and encouraged enrollment on clinical studies whenever possible.

184 Background: Prostate Specific Antigen (PSA) is a valuable prognostic and predictive biomarker in prostate cancer (PC). Currently, the significance of PSA at death is undefined. In this single institution retrospective study, we aim to characterize the significance of PSA at death in patients with metastatic castration-resistant prostate cancer (mCRPC). Methods: Using the Mount Sinai Genitourinary (GU) Cancer Biorepository, an IRB approved database containing all consented GU cancer patients seen between 2010-2018, we stratified patients into the following cohorts based on their PSA at death: < 10, 10-100, 100-1000, and > 1000 ng/ml. We excluded data of patients who had less than 3 visits to the Mount Sinai Hospital. A descriptive analysis was performed to assess clinical characteristics of disease, treatment response, and outcomes. Results: We identified 1097 PC patients, and 101 were found to be deceased following a diagnosis of mCRPC. Cohorts of higher PSA level at death were associated with: a lower Gleason score at diagnosis, a longer time to castration resistance, higher burden of metastatic disease at death (non-visceral and visceral), and longer OS in patients with mCRPC (see table). Conclusions: In this study, PSA at death is associated with several important clinical characteristics and outcome, including overall survival. These differences may be attributed to their underlying biologic behavior. These results are hypothesis generating, and larger studies will be needed to further assess the significance of these findings. [Table: see text]

563 Background: Advances in diagnostic and treatment modalities have resulted in better outcomes in metastatic renal cell carcinoma (mRCC) patients. With new therapies extending survival, we hypothesize that pattern of metastatic disease has evolved over time. We assessed the pattern of metastases as reported in baseline characteristics of prospective clinical trial patients between 1990 and 2018. Methods: This study identified all phase I-III mRCC therapeutic clinical trials published between January 1990 and July 2018 in PubMed and ClinicalTrials.gov. Studies that included patients with other cancers or did not report metastases were excluded. Data was stratified to examine differences in three listed treatment eras for first-line therapy. Linear regression models were used to evaluate temporal trends and subcategorized as either First Line Only treatments (FLO) or Second-Line and Beyond (SLB). Results: 127 clinical trials encompassing 16534 subjects were identified. Between 1990 and 2018, rates of lymph node metastases in the FLO population increased significantly at 1.03% per year ( P < 0.05). The rate of lung and liver metastases in FLO showed a trend of increase at 0.48% and 0.04% per year, respectively, but decreased -0.73% and -0.15% per year in the SLB population. Moreover, rate of bone metastasis showed a trend of increase in both populations, particularly between the VEGF/TKI and Immunotherapy/TKI eras in the SLB population (18.89% to 29.19%). Conclusions: Notable changes were found in the pattern of metastasis in patients with mRCC. Increasing rate of bone metastasis may warrant dedicated bone imaging for routine staging in patients with mRCC. These evolving patterns may have important implications in treatment selection and prognosis in this patient population. [Table: see text]

310 Background: Optimal sequencing of approved therapeutic agents in mCRPC is not known. The standard approach, is to treat until resistance then switch. The PRINT trial explores the efficacy of treating mCRPC with a rapidly-cycling, non-cross reactive regimen as a way to more effectively treat an intrinsically heterogeneous disease, to delay or prevent drug resistance, and minimize treatment toxicity. Methods: Patients were treated with 3 consecutive treatment modules, each of 12 weeks' duration: 1. abiraterone acetate 1000 mg PO daily and prednisone 5 mg PO BID; 2. cabazitaxel 20 mg/m2 IV and carboplatin AUC 4 IV q3 weeks; 3. enzalutamide 160 mg PO daily and radium-223 50 kBq/kg IV q4 weeks (in those with bone metastases). After completion of this 9 month regimen, patients are followed on ADT alone. Primary endpoint is PSA or radiographic time to disease progression. Results: From 3/2017 to 10/2018, 28 of 40 planned men with mCRPC were enrolled, 19 (67.9%) with bone metastases. PSA response rates ( > 90%/ > 50%), compared to baseline, following each treatment module: 1. 50%/78.6%; 2. 50%/92.7%; 3. 64.39%/92.7%. Currently, 14 patients have completed the study regimen with median follow up of 3.6 months, 8 of whom continue without any additional therapy. Of the patients evaluable for primary endpoint, median time to PSA progression is 96+ days (95% CI 82-110+ days). The regiment was well tolerated, grade 3/4 adverse effects include: hyperglycemia (17.9%), diarrhea (7.1%), anemia (3.6%), fatigue (3.6%), neutropenia (3.6%), thrombocytopenia (3.6%). Measurable response and molecular correlate data will be presented. Conclusions: Treatment of mCRPC with a rapidly-cycling non-cross reactive regimen is feasible, demonstrates significant antitumor benefits, and is well tolerated. Further follow up will determine if PRINT delays progression compared with standard approaches. Clinical trial information: NCT02903160.

309 Background: High prostate specific antigen (PSA) at diagnosis is associated with worse outcomes in patients (pt) with prostate cancer. However, treatment selection and clinical outcome in those diagnosed with an extremely high PSA (> 500 ng/ml) are not well characterized, and we aim to better study this unique pt population. Methods: Using the Mount Sinai Genitourinary (GU) Cancer Biorepository, an IRB approved database containing all consented GU cancer pts seen between 2010-2018, we identified 23 pts with a PSA >500 at prostate cancer diagnosis. Descriptive analysis was performed to capture clinical characteristics, treatment selection and response, and outcomes in this cohort. Results: The median age and PSA at diagnosis were 64 (54-85) and 1057 ng/ml (528-11,418). At presentation, 1 pt had localized versus 22 pts had metastatic disease, 3 were asymptomatic, and sites of metastasis included lymph nodes (LN) only (n=3), bone only (n=8), or LNs and bone (n=11). Pts were initiated on either first line androgen deprivation (ADT) or ADT plus docetaxel if seen after 2015 (1 refused). All pts had >90% PSA response to first line therapy, with median PSA nadir 4.38 ng/ml (0.06-153), duration of response 6 months (1-33), and time to castration-resistant prostate cancer (CRPC) 14.5 months (5-99). There are differences in treatment selection and outcomes for pts treated with ADT vs. ADT plus docetaxel first line (see table). Conclusions: In pts with PSA >500 at prostate cancer diagnosis, we have observed significant heterogeneity in clinical presentation and response to treatment. In pts treated with first line ADT plus docetaxel, we observed 2 of 7 pts with extended treatment response (> 42 months). Differences in disease biology may account for this observation, and molecular characterization will be needed to better understand this subset. [Table: see text]

467 Background: Stress-induced adrenergic signaling suppresses the immune system. A pre-clinical mouse model has shown that pharmacologic beta-blockade can stimulate CD8+ T-cell activity, and as a result improve efficacy of checkpoint inhibitors (CPI) to inhibit growth in solid tumors. Herein, we investigate the effect of BB on outcomes of patients receiving immunotherapy in mUC and mRCC. Methods: Using the Mount Sinai Genitourinary (GU) Cancer Biorepository, an IRB approved database containing all consented GU cancer patients seen between 2010-2018, we identified patients with either UC or RCC that have received CTLA-4 and/or PD-1/PD-L1 blockade. Patients who received only 1 dose of CPI were excluded from this analysis. A descriptive analysis was performed to assess clinical characteristics and treatment response. Overall Survival (OS) was calculated with Kaplan-Meier curves and cox proportional hazard models. Results: We identified 34 evaluable patients with mUC and 14 with mRCC that received CPI (Table). The median age at initiation was 69 years (39–91 years) and 81.2% (39/48) received prior chemotherapy and/or molecular targeted therapies. The mean duration of therapy was longer in the BB group compared to non-BB group (10.6 vs. 4.0 mo). For patients with mUC, the overall response rate (ORR) was 62.5% vs. 12.5% in favor of the BB group. For the patients with mRCC, the ORR was 40.0% vs. 10.0% in favor of the BB group. There were more outstanding responders (>1 year) in the BB group when compared with the non-BB group (41.2% vs. 6.5%). Patients with BB use had significantly improved median OS (NR vs. 11.6 mo, p = 0.004) when compared to those who did not receive BB. Conclusions: In this single-center cohort, the concurrent use of BB receiving CPI therapy is associated with an improved ORR, duration of therapy, and OS. Although this is hypothesis generating, the addition of BB is a promising strategy to improve response of immunotherapy, and prospective validation of this approach will be needed. [Table: see text]

In the recent MAINSAIL trial, addition of lenalidomide to docetaxel for metastatic castration-resistant prostate cancer (mCRPC) was associated with inferior overall survival and more toxicity; thus, lenalidomide joins a long line of agents that failed to improve the efficacy of docetaxel. The process by which new therapies are advanced to phase III studies, particularly in combination with docetaxel, should be re-examined.

Treatment of advanced prostate cancer has changed considerably in recent years, but the vast majority of advances have been made in patients with metastatic castration-resistant disease. There have been relatively fewer advances in the earlier, hormonally responsive stage of metastatic disease. Since the empiric establishment of androgen deprivation therapy as first-line therapy for metastatic prostate cancer decades ago, there have been multiple studies looking at variations of suppressing testosterone, but the overall paradigm has not been strongly challenged until more recently. In particular, the dramatic results reported by the CHAARTED trial not only bring chemotherapy to an arena historically dominated solely by hormonal therapy but also stimulate renewed efforts into improving upon our management of metastatic hormone-sensitive prostate cancer.

Purpose: Tremelimumab (ticilimumab, Pfizer), is a monoclonal antibody (mAb) targeting cytotoxic T lymphocyte–associated antigen-4 (CTLA-4). Ipilimumab (Yervoy, BMS), another anti-CTLA-4 antibody, is approved by the U.S. Federal Drug Administration (FDA). Biomarkers are needed to identify the subset of patients who will achieve tumor control with CTLA-4 blockade. Experimental Design: Pretreatment peripheral blood samples from 218 patients with melanoma who were refractory to prior therapy and receiving tremelimumab in a multicenter phase II study were measured for 169 mRNA transcripts using reverse transcription polymerase chain reaction (RT-PCR). A two-class latent model yielded a risk score based on four genes that were highly predictive of survival (P < 0.001). This signature was validated in an independent population of 260 treatment-naïve patients with melanoma enrolled in a multicenter phase III study of tremelimumab. Results: Median follow-up was 297 days for the training population and 386 days for the test population. Expression levels of the 169 genes were closely correlated across the two populations (r = 0.9939). A four-gene model, including cathepsin D (CTSD), phopholipase A2 group VII (PLA2G7), thioredoxin reductase 1 (TXNRD1), and interleukin 1 receptor–associated kinase 3 (IRAK3), predicted survival in the test population (P = 0.001 by log-rank test). This four-gene model added to the predictive value of clinical predictors (P < 0.0001). Conclusions: Expression levels of CTSD, PLA2G7, TXNRD1, and IRAK3 in peripheral blood are predictive of survival in patients with melanoma treated with tremelimumab. Blood mRNA signatures should be further explored to define patient subsets likely to benefit from immunotherapy. Clin Cancer Res; 20(12); 3310–8. ©2014 AACR.

Despite increasing early detection and treatment of prostate cancer, a subset of patients presents with or develops metastatic disease. Androgen deprivation therapy is effective but resistance eventually develops, resulting in a lethal phenotype known as castration-resistant prostate cancer (CRPC). Recently, several novel treatments, each with distinct mechanisms of actions, have been approved for the treatment of CRPC. Understanding of the metabolic and toxicological considerations of each treatment is crucial to the successful management of patients with this lethal disease.The present review focuses on the metabolism and toxicology characteristics of recently approved therapies in the treatment of metastatic CRPC. Specifically, the authors review the mechanism of action of these therapies in addition to their, efficacy and usage recommendations for hepatic and renal impairment. The authors, furthermore, also consider their adverse effect profile.Despite the expanding armamentarium of effective treatments for CRPC, the exact choice, timing and sequence of various therapies remains an inexact science and requires further investigation. Variations in patient comorbidities, disease burden, organ functions and adverse events are all critical determinants in selection of treatment. Identification and validation of molecular pathways and specific targets that drives disease progression will be critical in the continued development of effective treatments in advanced prostate cancer.

Lessons Learned The safety and activity findings of abiraterone acetate plus prednisone treatment in black men with mCRPC were similar to results from previously conducted studies with largely white populations. Poor trial accrual continues to be a challenge in black men with mCRPC and further efforts are needed to address such underrepresentation. Background. Self-identified black men have higher incidence and mortality from prostate cancer in the United States compared with white men but are dramatically underrepresented in clinical trials exploring novel therapies for metastatic castration-resistant prostate cancer (mCRPC). Methods. Black men with mCRPC were treated with abiraterone acetate (AA), 1,000 mg daily, and prednisone (P), 5 mg twice daily. The primary objective was to determine antitumor activity (defined by a ≥30% decline in prostate-specific antigen [PSA] level) and to correlate germline polymorphisms in androgen metabolism genes with antitumor activity. Secondary objectives included determining safety, post-treatment changes in measurable disease, and time to disease progression. Results. From April 2013 to March 2016, a total of 11 black men were enrolled and received AA plus P (AA+P); 7 of 10 evaluable patients were docetaxel naive. Post-treatment declines in PSA level of ≥30% were achieved in 90% of patients. The side effect profile was consistent with prior clinical trials exploring AA+P in mCRPC. Due to poor accrual, the study was closed prematurely with insufficient sample size for the planned pharmacogenetic analyses. Conclusion. In this small prospective study terminated for poor accrual, the safety and activity of AA+P in black men with mCRPC was similar to that reported in prior studies exploring AA in largely white populations. Further efforts are needed to address underrepresentation of black men in mCRPC trials.

166 Background: Prostate cancer is a heterogeneous disease with differences in tumor stromal interactions contributing to variability in treatment response and outcome. Gene expression of peripheral blood cells is altered by interactions with neoplastic tissue. We previously developed a peripheral whole blood six-gene signature prognostic for survival in mCRPC. Here we evaluate how different clinical disease states and treatment with different therapeutic agents impact this signature. Methods: Whole blood was collected in PAXgene Blood RNA tubes in two cohorts of prostate cancer patients, one at Mount Sinai (n=135), the other in Munich (n=59), in the context of prospective clinical studies. Whole blood RNA was extracted and the six target genes were amplified using qPCR. Scores were derived using normalized cycle threshold (ΔCT) values of the six genes, according to the model: 2 x ABL2 + SEMA4D + ITGAL – C1QA – TIMP1 – CDKN1A. Patients were categorized by disease state in the Mount Sinai cohort, and by treatment received in the Munich cohort, for data analysis. Results: CRPC is the only disease state with a mean six-gene score (18.06) above the high-risk cutoff (17.9), and is significantly higher than localized or hormone sensitive advanced disease (16.07, 16.52, respectively; p=0.0002). Among patients with localized disease, there was no significant difference in the mean six-gene scores for patients with low-, intermediate-, and high-risk disease (16.07, 15.33, 16.66, respectively; p=0.27). In CRPC patients treated with docetaxel, there are significant changes to the six-gene score over the course of treatment (p=0.002), with a notable percentage decrease (-6.2%) at the 2-8 week timepoint that is not observed in patients treated with abiraterone or enzalutamide. Conclusions: Gene expression profiling of whole blood is influenced by the clinical state of prostate cancer as seen by differences to the six-gene score from localized to castrate resistant disease. Cytotoxic chemotherapy appears to modulate the six-gene score, something not seen with AR-directed therapies. Further investigation will be needed to understand the significance of these changes.

170 Background: While satraplatin, a fourth generation oral platinum analogue, failed to improve overall survival (OS) in an unselected metastatic castrate-resistant prostate cancer (mCRPC) population (Sternberg, JCO 2009), anti-tumor activity was demonstrated, suggesting a “platinum-sensitive” subset of patients. Predictive biomarkers may not only select patients most likely to benefit from novel “targeted” therapies but also from standard (even discarded) cytotoxic agents. Development of predictive biomarkers in mCRPC is hampered by the fact that PC is associated with a long natural history and evolving genetic changes, highlighting the need for immediate pre-treatment metastatic tissue samples for biomarker development. In this trial, we sought to determine the feasibility of obtaining metastatic biopsies in patients with mCRPC treated with satraplatin. Methods: Docetaxel-refractory mCRPC patients underwent image-guided biopsy of metastatic lesions prior to treatment with satraplatin 80 mg/m2 PO on days 1 to 5 of a 35-day cycle and prednisone 5 mg PO twice daily. Biopsy samples are analyzed by whole exome and RNA sequencing, and peripheral blood samples are undergoing transcriptional profiling, to facilitate biomarker development. Results: Thirteen patients were enrolled with a median age of 71 (range: 55 to 80), prostate-specific antigen (PSA) of 82 ng/ml (0.04-3057), and Gleason score 8 (7 to 9). All patients received prior docetaxel, four (31%) had more than or eqaul to two prior chemotherapies, and two (15%) received abiraterone. Drug-related grade 3/4 toxicities included leukopenia (23%), neutropenia (8%), thrombocytopenia (8%), fatigue (8%), renal failure (8%), dysphagia (17%), and diarrhea (8%). A median of four cycles of satraplatin were completed, with declines of serum PSA of greater than or equal to 30% achieved in 4 of 13 patients (31%; 95% CI, 57.3 to 85.4%). Median time to PSA progression was 12.4 weeks (95% CI, 7.2 to 29.7+ weeks). Metastatic pre-treatment biopsies were collected in all study patients; genomic analysis is ongoing. Conclusions: This study confirms that satraplatin has anti-cancer activity in a subset of patients with mCRPC. Trials that require pre-treatment metastatic tumor biopsies are feasible. Analysis of the correlation between molecular signatures and treatment response will be presented at the meeting. Clinical trial information: NCT01289067.

9080 Background: Tremelimumab (Ticilimumumab, Pfizer), a monoclonal antibody targeting CTLA-4, a T cell inhibitory molecule, has shown activity in metastatic melanoma. Ipilimumab (Yervoy, BMS), another antibody targettingCTLA-4, improves survival relative to a peptide vaccine and is now FDA approved. A minority of patients will achieve durable tumor control with CTLA-4 blockade and biomarkers are urgently needed to identify those patients. Methods: 170 inflammatory, melanoma-specific and CTLA4-pathway related mRNA transcripts were measured using RT-PCR in pre-treatment peripheral blood samples from 218 patients with refractory melanoma receiving tremelimumab in a multi-center phase II study. A 2-class latent model yielded a risk score based on 4-genes that was highly predictive of survival (p