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Background. Patients (pts) with metastatic triple negative breast cancer (mTNBC) receive serial cytotoxic chemotherapy regimens, often with cumulative myelosuppressive effects, impairing treatment tolerance. Clonal hematopoiesis of indeterminate potential (CHIP) refers to the detection of somatic mutations in genes recurrently mutated in hematologic malignancies in the blood of adults with no evident hematologic abnormalities. Little is known about the natural history of CHIP after breast cancer treatment. We sought to characterize CHIP in pts undergoing treatment for mTNBC. Methods. In this retrospective cohort study we identified 149 pts with biopsy-proven mTNBC at a single tertiary care institution with at least one blood sample collected within six months of metastatic diagnosis. We performed targeted sequencing of cryopreserved peripheral blood mononuclear cell (PBMC)-derived genomic DNA and defined CHIP as the presence of at least one pathogenic somatic mutation present at variant allelic fraction (VAF) of 0.02-0.35. We assessed the relationship between CHIP status and overall survival (OS), demographics, clinicopathologic features, germline mutation status, and type and timing of therapy. Results. We identified 27 unique CHIP variants across 22/149 pts (15%) within six months of metastatic diagnosis. Frequency of mutated genes were as follows: DNMT3A (n=15), PPM1D (n=4), TP53 (n=3), TET2 (n=2), SRCAP (n=1), ZBTB33 (n=1), ZNF318 (n=1). Median follow-up in the cohort was 37.9 months (IQR: 23.9-Not reached). The median age at time of blood draw was 55 years (IQR: 8.5) for pts with CHIP vs. 51 years (IQR: 16.5) for pts without CHIP. Ten (45%) pts with CHIP and 47 (37%) pts without CHIP were current or former smokers. Two (9%) pts with CHIP and 10 (7.9%) pts without CHIP were known germline mutation carriers of BRCA1, BRCA2 or PALB2. Twenty-two (100%) pts with CHIP and 124 (98%) pts without CHIP had received systemic chemotherapy for mTNBC prior to blood draw. There were no significant differences in type of chemotherapy regimen received between patients with or without CHIP. Twenty (90.9%) pts with CHIP vs. 96 (75.6%) of pts without CHIP had received radiation therapy prior to blood draw. Pts with CHIP had similar OS to those without CHIP (median OS 7.75 [2.20-31.7] vs. 9.33 [8.02-11.73] months). No pts developed therapy-related myeloid neoplasms (t-MN) or died of complications of cardiac disease. Conclusions. Pts with mTNBC had a higher frequency of CHIP than previously reported in age-matched healthy populations, but similar CHIP prevalence to what has been seen in cohorts of pts with solid tumors. Our study assessed for the presence of CHIP at only a single time point early in the metastatic course, but serial blood sampling later in treatment might reveal additional cases of CHIP. Though this cohort of patients with life-limiting mTNBC was small, presence of CHIP in the first six months of metastatic diagnosis was not associated with worse survival. Citation Format: Katheryn Santos, Qingchun Jin, Peter G. Miller, Ashka Patel, Gregory J. Kirkner, Janet L. Files, Melissa E. Hughes, Samantha M. Stokes, Nabihah Tayob, Daniel G. Stover, Christopher J. Gibson, Eric P. Winer, Nancy U. Lin, Judy E. Garber, Heather A. Parsons. Clonal hematopoiesis of indeterminate potential (CHIP) in metastatic triple negative breast cancer [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P3-08-01.

Purpose: We had previously reported on the safety and the recommended phase 2 dose (RP2D) of olaparib in combination with the PI3Kα-specific inhibitor alpelisib in patients with high-grade serous ovarian cancer as studied in a phase 1b trial (NCT01623349). Here, we report on the breast cancer cohort from that study. Patients and Methods: Eligible patients had recurrent triple-negative breast cancer (TNBC) or recurrent breast cancer of any subtype with a germline BRCA mutation and were enrolled to a dose-escalation or -expansion cohort. After definition of the RP2D, secondary end points included safety and objective response rate (ORR). Exploratory analyses were performed using circulating-free DNA (cfDNA). Results: Seventeen patients with TNBC were enrolled with a median of three prior lines of chemotherapy. The most common treatment-related grade 3–4 adverse events were hyperglycemia (18%) and rash (12%). The ORR was 18% (23% for patients treated at the RP2D) and 59% had disease control. The median duration of response was 7.4 months. Analysis of cfDNA tumor fractions (TFx) revealed that patients with TFx < 15% after completion of the first cycle had a longer progression-free survival compared with those with TFx ≥ 15% (6.0 vs. 0.9 months; P = 0.0001). Conclusions: Alpelisib in combination with olaparib is tolerable in patients with pre-treated TNBC, with evidence of activity in non-BRCA carriers. cfDNA provided important prognostic information. Results highlight potential synergistic use of a PI3K inhibitor to sensitize HR-proficient (BRCA wild-type) TNBC to PARP inhibition and suggest the potential to expand the use of PARP inhibition beyond BRCA-mutant tumors.

PURPOSE Palbociclib is a cyclin-dependent kinase 4 and 6 inhibitor approved for advanced breast cancer. In the adjuvant setting, the potential value of adding palbociclib to endocrine therapy for hormone receptor–positive breast cancer has not been confirmed. PATIENTS AND METHODS In the prospective, randomized, phase III PALLAS trial, patients with hormone receptor–positive, human epidermal growth factor receptor 2–negative early breast cancer were randomly assigned to receive 2 years of palbociclib (125 mg orally once daily, days 1-21 of a 28-day cycle) with adjuvant endocrine therapy or adjuvant endocrine therapy alone (for at least 5 years). The primary end point of the study was invasive disease-free survival (iDFS); secondary end points were invasive breast cancer–free survival, distant recurrence-free survival, locoregional cancer-free survival, and overall survival. RESULTS Among 5,796 patients enrolled at 406 centers in 21 countries worldwide over 3 years, 5,761 were included in the intention-to-treat population. At the final protocol-defined analysis, at a median follow-up of 31 months, iDFS events occurred in 253 of 2,884 (8.8%) patients who received palbociclib plus endocrine therapy and in 263 of 2,877 (9.1%) patients who received endocrine therapy alone, with similar results between the two treatment groups (iDFS at 4 years: 84.2% v 84.5%; hazard ratio, 0.96; CI, 0.81 to 1.14; P = .65). No significant differences were observed for secondary time-to-event end points, and subgroup analyses did not show any differences by subgroup. There were no new safety signals for palbociclib in this trial. CONCLUSION At this final analysis of the PALLAS trial, the addition of adjuvant palbociclib to standard endocrine therapy did not improve outcomes over endocrine therapy alone in patients with early hormone receptor–positive breast cancer.

Purpose:HER2 mutations (HER2mut) induce endocrine resistance in estrogen receptor–positive (ER+) breast cancer.Patients and Methods:In this single-arm multi-cohort phase II trial, we evaluated the efficacy of neratinib plus fulvestrant in patients with ER+/HER2mut, HER2 non-amplified metastatic breast cancer (MBC) in the fulvestrant-treated (n = 24) or fulvestrant-naïve cohort (n = 11). Patients with ER-negative (ER−)/HER2mut MBC received neratinib monotherapy in an exploratory ER− cohort (n = 5).Results:The clinical benefit rate [CBR (95% confidence interval)] was 38% (18%–62%), 30% (7%–65%), and 25% (1%–81%) in the fulvestrant-treated, fulvestrant-naïve, and ER− cohorts, respectively. Adding trastuzumab at progression in 5 patients resulted in three partial responses and one stable disease ≥24 weeks. CBR appeared positively associated with lobular histology and negatively associated with HER2 L755 alterations. Acquired HER2mut were detected in 5 of 23 patients at progression.Conclusions:Neratinib and fulvestrant are active for ER+/HER2mut MBC. Our data support further evaluation of dual HER2 blockade for the treatment of HER2mut MBC.

PURPOSE We aimed to improve efficacy and reduce toxicity of high-risk human epidermal growth factor receptor 2 (HER2)–positive early breast cancer (EBC) treatment by replacing taxanes and trastuzumab with trastuzumab emtansine (T-DM1). METHODS The phase III KAITLIN study ( NCT01966471 ) included adults with excised HER2-positive EBC (node-positive or node-negative, hormone receptor–negative, and tumor > 2.0 cm). Postsurgery, patients were randomly assigned 1:1 to anthracycline-based chemotherapy (three-four cycles) and then 18 cycles of T-DM1 plus pertuzumab (AC-KP) or taxane (three-four cycles) plus trastuzumab plus pertuzumab (AC-THP). Adjuvant radiotherapy/endocrine therapy was permitted. Coprimary end points were invasive disease-free survival (IDFS) in the intention-to-treat node-positive and overall populations with hierarchical testing. RESULTS The median follow-up was 57.1 months (interquartile range, 52.1-60.1 months) for AC-THP (n = 918) and 57.0 months (interquartile range, 52.1-59.8 months) for AC-KP (n = 928). There was no significant IDFS difference between arms in the node-positive (n = 1,658; stratified hazard ratio [HR], 0.97; 95% CI, 0.71 to 1.32) or overall population (n = 1846; stratified HR, 0.98; 95% CI, 0.72 to 1.32). In the overall population, the three-year IDFS was 94.2% (95% CI, 92.7 to 95.8) for AC-THP and 93.1% (95% CI, 91.4 to 94.7) for AC-KP. Treatment completion rates (ie, 18 cycles) were 88.4% for AC-THP and 65.0% for AC-KP (difference driven by T-DM1 discontinuation because of laboratory abnormalities [12.5%]). Similar rates of grade ≥ 3 (55.4% v 51.8%) and serious adverse events (23.3% v 21.4%) occurred with AC-THP and AC-KP, respectively. KP decreased clinically meaningful deterioration in global health status versus THP (stratified HR, 0.71; 95% CI, 0.62 to 0.80). CONCLUSION The primary end point was not met. Both arms achieved favorable IDFS. Trastuzumab plus pertuzumab plus chemotherapy remains the standard of care for high-risk HER2-positive EBC.

Clinical trials frequently include multiple end points that mature at different times. The initial report, typically based on the primary end point, may be published when key planned co-primary or secondary analyses are not yet available. Clinical Trial Updates provide an opportunity to disseminate additional results from studies, published in JCO or elsewhere, for which the primary end point has already been reported. The combined analysis of SOFT-TEXT compared outcomes in 4,690 premenopausal women with estrogen/progesterone receptor–positive (ER/PgR+) early breast cancer randomly assigned to 5 years of exemestane + ovarian function suppression (OFS) versus tamoxifen + OFS. After a median follow-up of 9 years, exemestane + OFS significantly improved disease-free survival (DFS) and distant recurrence-free interval (DRFI), but not overall survival, compared with tamoxifen + OFS. We now report DFS, DRFI, and overall survival after a median follow-up of 13 years. In the intention-to-treat (ITT) population, the 12-year DFS (4.6% absolute improvement, hazard ratio [HR], 0.79; 95% CI, 0.70 to 0.90; P < .001) and DRFI (1.8% absolute improvement, HR, 0.83; 95% CI, 0.70 to 0.98; P = .03), but not overall survival (90.1% v 89.1%, HR, 0.93; 95% CI, 0.78 to 1.11), continued to be significantly improved for patients assigned exemestane + OFS over tamoxifen + OFS. Among patients with human epidermal growth factor receptor 2-negative tumors (86.0% of the ITT population), the absolute improvement in 12-year overall survival with exemestane + OFS was 2.0% (HR, 0.85; 95% CI, 0.70 to 1.04) and 3.3% in those who received chemotherapy (45.9% of the ITT population). Overall survival benefit was clinically significant in high-risk patients, eg, women age < 35 years (4.0%) and those with > 2 cm (4.5%) or grade 3 tumors (5.5%). These sustained reductions of the risk of recurrence with adjuvant exemestane + OFS, compared with tamoxifen + OFS, provide guidance for selecting patients for whom exemestane should be preferred over tamoxifen in the setting of OFS. [Media: see text]

The Breast Cancer Weight Loss (BWEL) trial, is a randomized, controlled trial designed to determine whether weight loss after breast cancer diagnosis can reduce the risk of cancer recurrence in women with overweight or obesity. BWEL will compare the efficacy of a telephone-based, weight loss intervention plus health education materials versus health education materials alone on invasive disease-free survival in 3181 women with stage II-III breast cancer and a body mass index (BMI) >27 kg/m(2). In this report, we provide a detailed description of the goals and methods of the lifestyle intervention and the evidence supporting the intervention used in the BWEL trial. The intervention’s primary goal for participants is to achieve and maintain a weight loss of ≥ 10% of baseline weight through increased physical activity and caloric restriction. The evidence supporting the diet, physical activity and behavioral components of this telephone-based weight loss intervention as well as strategies to promote participant engagement and retention are described. The intervention is provided through 42 sessions, delivered by trained health coaches, over a 2-year period. If the BWEL lifestyle intervention is successful in improving cancer outcomes, then weight loss will be incorporated into the care of thousands of breast cancer patients.

Clinical trials frequently include multiple end points that mature at different times. The initial report, typically based on the primary end point, may be published when key planned co-primary or secondary analyses are not yet available. Clinical Trial Updates provide an opportunity to disseminate additional results from studies, published in JCO or elsewhere, for which the primary end point has already been reported. The Suppression of Ovarian Function Trial (SOFT; ClinicalTrials.gov identifier: NCT00066690 ) randomly assigned premenopausal women with hormone receptor–positive breast cancer to 5 years of adjuvant tamoxifen, tamoxifen plus ovarian function suppression (OFS), or exemestane plus OFS. The primary analysis compared disease-free survival (DFS) between tamoxifen plus OFS versus tamoxifen alone; exemestane plus OFS versus tamoxifen was a secondary objective. After 8 years, SOFT reported a significant reduction in recurrence and improved overall survival (OS) with adjuvant tamoxifen plus OFS versus tamoxifen alone. Here, we report outcomes after median follow-up of 12 years. DFS remained significantly improved with tamoxifen plus OFS versus tamoxifen (hazard ratio, 0.82; 95% CI, 0.69 to 0.98) with a 12-year DFS of 71.9% with tamoxifen, 76.1% with tamoxifen plus OFS, and 79.0% with exemestane plus OFS. OS was improved with tamoxifen plus OFS versus tamoxifen (hazard ratio, 0.78; 95% CI, 0.60 to 1.01) and was 86.8% with tamoxifen, 89.0% with tamoxifen plus OFS, and 89.4% with exemestane plus OFS at 12 years. Among those who received prior chemotherapy for human epidermal growth factor receptor-2–negative tumors, OS was 78.8% with tamoxifen, 81.1% with tamoxifen plus OFS, and 84.4% with exemestane plus OFS. In conclusion, after 12 years, there remains a benefit from including OFS in adjuvant endocrine therapy, with an absolute improvement in OS more apparent with higher baseline risk of recurrence. [Media: see text]

The 17th St Gallen International Breast Cancer Consensus Conference in 2021 was held virtually, owing to the global COVID-19 pandemic. More than 3300 participants took part in this important bi-annual critical review of the 'state of the art' in the multidisciplinary care of early-stage breast cancer. Seventy-four expert panelists (see Appendix 1) from all continents discussed and commented on the previously elaborated consensus questions, as well as many key questions on early breast cancer diagnosis and treatment asked by the audience. The theme of this year's conference was 'Customizing local and systemic therapies.' A well-organized program of pre-recorded symposia, live panel discussions and real-time panel voting results drew a worldwide audience of thousands, reflecting the farreaching impact of breast cancer on every continent. The interactive technology platform allowed, for the first time, audience members to ask direct questions to panelists, and to weigh in with their own vote on several key panel questions. A hallmark of this meeting was to focus on customized recommendations for treatment of early-stage breast cancer. There is increasing recognition that the care of a breast cancer patient depends on highly individualized clinical features, including the stage at presentation, the biological subset of breast cancer, the genetic factors that may underlie breast cancer risk, the genomic signatures that inform treatment recommendations, the extent of response before surgery in patients who receive neoadjuvant therapy, and patient preferences. This customized approach to treatment requires integration of clinical care between patients and radiology, pathology, genetics, and surgical, medical and radiation oncology providers. It also requires a dynamic response from clinicians as they encounter accumulating clinical information at the time of diagnosis and then serially with each step in the treatment plan and follow-up, reflecting patient experiences and treatment response.

Background In early trials, hypersensitivity reactions (HSRs) to paclitaxel were common, thus prompting the administration of antihistamines and corticosteroids before every paclitaxel dose. We tested the safety of omitting corticosteroids after cycle 2 during the paclitaxel portion of the dose‐dense (DD) doxorubicin‐cyclophosphamide (AC)–paclitaxel regimen. Patients, Materials, and Methods In this prospective, single‐arm study, patients who completed four cycles of DD‐AC for stage I–III breast cancer received paclitaxel 175 mg/m2 every 2 weeks for four cycles. Patients received a standard premedication protocol containing dexamethasone, diphenhydramine, and a histamine H2 blocker prior to the first two paclitaxel cycles. Dexamethasone was omitted in cycles three and four if there were no HSRs in previous cycles. We estimated the rate of grade 3–4 HSRs. Results Among 127 patients enrolled, 125 received more than one dose of protocol therapy and are included in the analysis. Fourteen (11.2%; 90% confidence interval, 6.9%–20.0%) patients had any‐grade HSRs, for a total of 22 (4.5%; 3.1%–6.4%) HSRs over 486 paclitaxel cycles. Any‐grade HSRs occurred in 1.6% (0.3%–5.0%), 6.5% (3.3%–11.3%), 7.4% (3.9%–12.5%), and 2.6% (0.7%–6.6%) of patients after paclitaxel cycles 1, 2, 3, and 4, respectively. Dexamethasone use was decreased by 92.8% in cycles 3 and 4. Only one patient experienced grade 3 HSR in cycles 3 or 4, for a rate of grade 3/4 HSR 0.4% (0.02%–2.0%) (1/237 paclitaxel infusions). That patient had grade 2 HSR during cycle 2, and the subsequent grade 3 event occurred despite usual dexamethasone premedication. A sensitivity analysis restricted to patients not known to have received dexamethasone in cycles 3 and 4 found that any‐grade HSRs occurred in 2.7% (3/111; 0.7%–6.8%) and 0.9% (1/109; 0.05%–4.3%) of patients in cycle 3 and 4, respectively. Conclusion Corticosteroid premedication can be safely omitted in cycles 3 and 4 of dose‐dense paclitaxel if HSRs are not observed during cycles 1 and 2. Implications for Practice Because of the potential for hypersensitivity reactions (HSRs) to paclitaxel, corticosteroids are routinely prescribed prior to each dose, on an indefinite basis. This prospective study, including 125 patients treated with 486 paclitaxel cycles, demonstrates that corticosteroids can be safely omitted in future cycles if HSRs did not occur during cycles 1 and 2 of paclitaxel and that this strategy reduces the use of corticosteroids in cycles 3 and 4 by 92.8% relative to current standard of care., To avoid hypersensitivity reactions, corticosteroids are routinely prescribed before each dose of paclitaxel. This article reports the results of a study that focused on whether corticosteroids could be safely omitted in later cycles of treatment if reactions did not occur during earlier cycles.

Immune checkpoint inhibitors (ICIs) have minimal therapeutic effect in hormone receptor-positive (HR+ ) breast cancer. We present final overall survival (OS) results (n = 88) from a randomized phase 2 trial of eribulin ± pembrolizumab for patients with metastatic HR+ breast cancer, computationally dissect genomic and/or transcriptomic data from pre-treatment tumors (n = 52) for molecular associations with efficacy, and identify cytokine changes differentiating response and ICI-related toxicity (n = 58). Despite no improvement in OS with combination therapy (hazard ratio 0.95, 95% CI 0.59–1.55, p = 0.84), immune infiltration and antigen presentation distinguished responding tumors, while tumor heterogeneity and estrogen signaling independently associated with resistance. Moreover, patients with ICI-related toxicity had lower levels of immunoregulatory cytokines. Broadly, we establish a framework for ICI response in HR+ breast cancer that warrants diagnostic and therapeutic validation. ClinicalTrials.gov Registration: NCT03051659., A randomized phase 2 clinical trial has recently shown no benefit of the combination eribulin and pembrolizumab over pembrolizumab alone in HR + metastatic breast cancer patients (NCT03051659). Here, the authors are reporting the final OS data and biomarker analyses on a subset of samples to analyze molecular correlates

In the ATEMPT trial, adjuvant trastuzumab emtansine (T-DM1) compared to paclitaxel plus trastuzumab (TH) for stage I HER2-positive breast cancer improved patient-reported outcomes (PROs), while maintaining excellent disease outcomes. We report treatment discontinuation and use multivariable models to compare, patient-reported toxicity and quality-of-life (QOL) by age (≤50, >50) and treatment arm at 18 months post-enrollment among 366 eligible participants randomized in a 3:1 ratio to T-DM1 or TH. T-DM1 discontinuation was higher among women >50 vs. ≤50 (23% vs. 9%, p = 0.003, Fisher’s Exact test) with 4%, 8%, and 17% of older patients discontinuing treatment by 3, 6, and 9 months, respectively. Superior QOL with T-DM1 vs. TH was observed among women ≤50 with estimated mean difference of 6.48 (95% confidence interval (CI) 0.51–12.46) and driven by better social/family well-being and breast cancer-specific sub-scores. Among women >50, T-DM1 was associated with superior physical well-being and less activity impairment, with no differences in global QOL. Older women had decreased neuropathy with T-DM1 vs. TH. De-escalated treatment regimens for HER2 positive breast cancer may have age-varying impact on treatment tolerance, toxicities and subsequent QOL, which should be considered when selecting therapy options.Clinical Trial Registration: ClinicalTrials.gov, NCT01853748

PURPOSEThe Standardized Definitions for Efficacy End Points (STEEP) criteria, established in 2007, provide standardized definitions of adjuvant breast cancer clinical trial end points. Given the evolution of breast cancer clinical trials and improvements in outcomes, a panel of experts reviewed the STEEP criteria to determine whether modifications are needed.METHODSWe conducted systematic searches of ClinicalTrials.gov for adjuvant systemic and local-regional therapy trials for breast cancer to investigate if the primary end points reported met STEEP criteria. On the basis of common STEEP deviations, we performed a series of simulations to evaluate the effect of excluding non–breast cancer deaths and new nonbreast primary cancers from the invasive disease–free survival end point.RESULTSAmong 11 phase III breast cancer trials with primary efficacy end points, three had primary end points that followed STEEP criteria, four used STEEP definitions but not the corresponding end point names, and four used end points that were not included in the original STEEP manuscript. Simulation modeling demonstrated that inclusion of second nonbreast primary cancer can increase the probability of incorrect inferences, can decrease power to detect clinically relevant efficacy effects, and may mask differences in recurrence rates, especially when recurrence rates are low.CONCLUSIONWe recommend an additional end point, invasive breast cancer–free survival, which includes all invasive disease–free survival events except second nonbreast primary cancers. This end point should be considered for trials in which the toxicities of agents are well-known and where the risk of second primary cancer is small. Additionally, we provide end point recommendations for local therapy trials, low-risk populations, noninferiority trials, and trials incorporating patient-reported outcomes.

We evaluated the efficacy and safety of poly-(adenosine diphosphate-ribose) polymerase (PARP) 1 and 2 inhibitor veliparib and temozolomide in metastatic breast cancer patients with and without germline BRCA1/2 mutations. In this single-arm phase II trial, patients with metastatic breast cancer received veliparib 30 to 40 mg twice daily on days 1 to 7 with concurrent temozolomide 150 mg/m2 on days 1 to 5 of a 28-day cycle. The primary cohort was unselected for BRCA mutation status, and an expansion cohort enrolled only BRCA1/2 carriers. The primary endpoint was objective response rate (ORR) in each cohort. Secondary endpoints included progression-free survival (PFS), clinical benefit rate (CBR), and evaluation of safety and tolerability. In the primary cohort of 41 unselected patients, which included 9 BRCA mutation carriers, the ORR was 10% and clinical benefit rate at 4 months (CBR) was 27%. In the expansion cohort of 21 BRCA1/2 carriers, the ORR was 14% and CBR was 43%. Among all 30 BRCA1/2 carriers, the ORR was 23% versus 0% among non-carriers. In the subset of BRCA1/2 carriers, the ORR was 32% among platinum-naive patients versus 9% among platinum-exposed patients. The median PFS was 3.3 months among BRCA1/2 carriers compared to 1.8 months among non-carriers (HR: 0.48, p = 0.006). A longer median PFS of 6.2 months was observed among BRCA1/2 carriers who had no prior platinum therapy. The most common grade 3 and 4 toxicities were thrombocytopenia (32%) and neutropenia (21%) that generally improved with dose modifications. Veliparib and temozolomide demonstrated clinical activity in platinum-naive BRCA-associated metastatic breast cancer with manageable toxicity at doses of veliparib well below the single-agent active dose. Although the study did not meet its primary endpoint in unselected nor BRCA-associated breast cancer, this regimen was further evaluated in the BROCADE 2 study. NCT01009788 (ClinicalTrials.gov), November 9, 2009

Mutations in the Janus Kinase 2 (JAK2) gene resulting in constitutive kinase activation represent the most common genetic event in myeloproliferative neoplasms (MPN), a group of diseases involving overproduction of one or more kinds of blood cells, including red cells, white cells, and platelets. JAK2 kinase inhibitors, such as ruxolitinib, provide clinical benefit, but inhibition of wild-type (wt) JAK2 limits their clinical utility due to toxicity to normal cells, and small molecule inhibition of mutated JAK2 kinase activity can lead to drug resistance. Here, we present a strategy to target mutated JAK2 for degradation, using the cell's intracellular degradation machinery, while sparing non-mutated JAK2. We employed a chemical genetics screen, followed by extensive selectivity profiling and genetic studies, to identify the deubiquitinase (DUB), JOSD1, as a novel regulator of mutant JAK2. JOSD1 interacts with and stabilizes JAK2-V617F, and inactivation of the DUB leads to JAK2-V617F protein degradation by increasing its ubiquitination levels, thereby shortening its protein half-life. Moreover, targeting of JOSD1 leads to the death of JAK2-V617F-positive primary acute myeloid leukemia (AML) cells. These studies provide a novel therapeutic approach to achieving selective targeting of mutated JAK2 signaling in MPN.

Background In the phase III IMpassion130 study, atezolizumab plus nab-paclitaxel (A+nP) showed clinical benefit in advanced or metastatic triple-negative breast cancer patients who were programmed death-ligand 1 (PD-L1)+ (tumor-infiltrating immune cells [IC] ≥1%) using the SP142 immunohistochemistry assay. Here we evaluate 2 other PD-L1 assays for analytical concordance with SP142 and patient-associated clinical outcomes. Methods Samples from 614 patients (68.1% of intention-to-treat population) were centrally evaluated by immunohistochemistry for PD-L1 status on IC (VENTANA SP142, SP263, Dako 22C3) or as a combined positive score (CPS; 22C3). Results Using SP142, SP263, and 22C3 assays, PD-L1 IC ≥1% prevalence was 46.4% (95% confidence interval [CI] = 42.5% to 50.4%), 74.9% (95% CI = 71.5% to 78.3%), and 73.1% (95% CI = 69.6% to 76.6%), respectively; 80.9% were 22C3 CPS ≥1. At IC ≥1% (+), the analytical concordance between SP142 and SP263 and 22C3 was 69.2% and 68.7%, respectively. Almost all SP142+ cases were captured by other assays (double positive), but several SP263+ (29.6%) or 22C3+ (29.0%) cases were SP142– (single positive). A+nP clinical activity vs placebo+nP in SP263+ and 22C3+ patients (progression-free survival [PFS] hazard ratios [HRs] = 0.64 to 0.68; overall survival [OS] HRs = 0.75 to 0.79) was driven by double-positive cases (PFS HRs = 0.60 to 0.61; OS HRs = 0.71 to 0.75) rather than single-positive cases (PFS HRs = 0.68 to 0.81; OS HRs = 0.87 to 0.95). Concordance for harmonized cutoffs for SP263 (IC ≥4%) and 22C3 (CPS ≥10) to SP142 (IC ≥1%) was subpar (approximately 75%). Conclusions 22C3 and SP263 assays identified more patients as PD-L1+ (IC ≥1%) than SP142. No inter-assay analytical equivalency was observed. Consistent improved A+nP efficacy was captured by the SP142 PD-L1 IC ≥1% subgroup nested within 22C3 and SP263 PD-L1+ (IC ≥1%) populations.

Breast cancer mortality in women has declined significantly over the past several years. In men, it is unclear whether survival has changed over time. We evaluated changes in breast cancer-specific survival (BCSS) and overall survival (OS) in male breast cancer (MaBC) over the past 3 decades.We evaluated men diagnosed with breast cancer between 1988 and 2017, reported in the Surveillance, Epidemiology, and End Results registry. Patients were categorized into 3 groups by year of diagnosis: 1988-1997, 1998-2007 and 2008-2017. BCSS and OS were estimated by Kaplan-Meier and differences between groups were compared by log-rank test. Multivariable Cox regression evaluated the independent association of year of diagnosis with BCSS and OS. All tests were 2-sided.We included 8,481 men. Overall, BCSS at 5 years was 83.69%, 83.78% and 84.41% in groups 1988-1997, 1998-2007 and 2008-2017, respectively; P=.86. There was no significant difference in BCSS between the 3 groups within each stage of disease. Among all patients, OS at 5 years was 64.61%, 67.31% and 69.05% in groups 1988-1997, 1998-2007 and 2008-2017, respectively; P=.01. In adjusted Cox models, each additional year of diagnosis had no significant association with BCSS (hazard ratio, 1.00; 95% confidence interval: 0.99-1.01; P=.75), but there was significant improvement in OS (hazard ratio, 0.99; 95% CI: 0.98-0.99; P=.009).Over the past 3 decades, there has been no significant improvement in BCSS in MaBC. Changes in OS over time are consistent with increasing life expectancy. Efforts to improve BCSS in MaBC are warranted.

PURPOSE In metastatic triple-negative breast cancer (mTNBC), consistent biomarkers of immune checkpoint inhibitor (ICI) therapy benefit remain elusive. We evaluated the immune, genomic, and transcriptomic landscape of mTNBC in patients treated with ICIs. METHODS We identified 29 patients with mTNBC treated with pembrolizumab or atezolizumab, either alone (n = 9) or in combination with chemotherapy (n = 14) or targeted therapy (n = 6), who had tumor tissue and/or blood available before ICI therapy for whole-exome sequencing. RNA sequencing and CIBERSORTx-inferred immune population analyses were performed (n = 20). Immune cell populations and programmed death-ligand 1 expression were assessed using multiplexed immunofluorescence (n = 18). Clonal trajectories were evaluated via serial tumor/circulating tumor DNA whole-exome sequencing (n = 4). Association of biomarkers with progression-free survival and overall survival (OS) was assessed. RESULTS Progression-free survival and OS were longer in patients with high programmed death-ligand 1 expression and tumor mutational burden. Patients with longer survival also had a higher relative inferred fraction of CD8+ T cells, activated CD4+ memory T cells, M1 macrophages, and follicular helper T cells and enrichment of inflammatory gene expression pathways. A mutational signature of defective repair of DNA damage by homologous recombination was enriched in patients with both shorter OS and primary resistance. Exploratory analysis of clonal evolution among four patients treated with programmed cell death protein 1 blockade and a tyrosine kinase inhibitor suggested that clonal stability post-treatment was associated with short time to progression. CONCLUSION This study identified potential biomarkers of response to ICIs among patients with mTNBC: high tumor mutational burden; presence of CD8+, CD4 memory T cells, follicular helper T cells, and M1 macrophages; and inflammatory gene expression pathways. Pretreatment deficiencies in the homologous recombination DNA damage repair pathway and the absence of or minimal clonal evolution post-treatment may be associated with worse outcomes.

Neoadjuvant chemotherapy (NAC) is standard for many females with breast cancer (FBC). The efficacy of NAC in male breast cancer (MaBC) is unclear. The aim of this study was to compare proportions of pathologic complete response (pCR) between MaBC and FBC by tumor subtype (TS).MaBC and FBC treated with NAC between 2010 and 2016, with known TS, were evaluated from the National Cancer Database. Proportions of pCR (ypT0/Tis ypN0) were compared between sexes within TS by Fisher test. Multivariable logistic regression assessed the independent association of sex with pCR. Overall survival (OS) was estimated by Kaplan-Meier.A total of 385 MaBC and 68,065 FBC were included. Median time from initiation of NAC to surgery was 143 days in MaBC and 148 days in FBC. Proportions of pCR in MaBC and FBC by TS were: hormone receptor-positive/human epidermal growth factor receptor 2-negative (HR+/HER2-): 4.9% vs 9.7%, p = .01; HR+/HER2+: 16.1% vs 33.6%, p .001; HR-/HER2+: 44.0% vs 53.2%, p = .42; and HR-/HER2-: 21.4% vs 32.1%, p = .18, respectively. FBC had twice the odds of pCR than MaBC (adjusted odds ratio, 2.0; 95% CI, 1.5-2.8; p .001). Five-year OS for MaBC with pCR vs not was 90% vs 64.7%; p = .02. Five-year OS for FBC with pCR vs not was 91.9% vs 75.3%; p .01.Proportions and odds of pCR to NAC were numerically lower in MaBC compared with FBC for each TS and statistically significant for HR+/HER2- and HR+/HER2+. The independent association of sex with pCR was confirmed in multivariable analysis. pCR is prognostic in both MaBC and FBC.

Background Triple-negative breast cancer (TNBC) is a heterogeneous disease and we have previously shown that rapid relapse of TNBC is associated with distinct sociodemographic features. We hypothesized that rapid versus late relapse in TNBC is also defined by distinct clinical and genomic features of primary tumors. Methods Using three publicly-available datasets, we identified 453 patients diagnosed with primary TNBC with adequate follow-up to be characterized as ‘rapid relapse’ (rrTNBC; distant relapse or death ≤2 years of diagnosis), ‘late relapse’ (lrTNBC; > 2 years) or ‘no relapse’ (nrTNBC: > 5 years no relapse/death). We explored basic clinical and primary tumor multi-omic data, including whole transcriptome (n = 453), and whole genome copy number and mutation data for 171 cancer-related genes (n = 317). Association of rapid relapse with clinical and genomic features were assessed using Pearson chi-squared tests, t-tests, ANOVA, and Fisher exact tests. We evaluated logistic regression models of clinical features with subtype versus two models that integrated significant genomic features. Results Relative to nrTNBC, both rrTNBC and lrTNBC had significantly lower immune signatures and immune signatures were highly correlated to anti-tumor CD8 T-cell, M1 macrophage, and gamma-delta T-cell CIBERSORT inferred immune subsets. Intriguingly, lrTNBCs were enriched for luminal signatures. There was no difference in tumor mutation burden or percent genome altered across groups. Logistic regression mModels that incorporate genomic features significantly outperformed standard clinical/subtype models in training (n = 63 patients), testing (n = 63) and independent validation (n = 34) cohorts, although performance of all models were overall modest. Conclusions We identify clinical and genomic features associated with rapid relapse TNBC for further study of this aggressive TNBC subset.

Male breast cancer is an uncommon disease, and population-based information regarding prognostic factors is limited. Most cases are hormone receptor (HR) positive; however, the association of tumor subtype with overall survival (OS) and breast cancer-specific survival (BCSS) is unclear. Using SEER data, we identified men with invasive breast cancer between 2010 and 2017 with known HR and HER2 status. We examined tumor subtypes by patient characteristics and performed multivariate Cox proportional hazards analyses to determine the associations of each variable with OS and BCSS. We included 2389 men with a median follow-up of 43 months (IQR 19–68). Median age was 66 years. Tumor subtype distribution was 84.1% HR+/HER2−, 12.7% HR+/HER2+ , 0.8% HR−/HER2+, and 2.3% triple-negative (TN). In univariate analysis, OS at 5 years was 76.5% for HR+/HER2−, 65.1% for HR+/HER2+ , 84.2% for HR-/HER2+, and 48.1% for TN (p

We aimed to report the 20-year risk of breast cancer-specific mortality (BCSM), report the risk of BCSM conditional on having survived 5 years, and identify factors associated with late deaths in stage III breast cancer. Using Surveillance, Epidemiology, and End Results data, we included women with stage III breast cancer diagnosed from 1990 to 2005. We excluded women with unknown hormone receptor (HR) status, women who did not undergo resection of the primary tumor or axillary nodes, or unknown cause of death. We estimated risks of BCSM using cumulative incidence function and used Fine and Gray regression to identify factors associated with late deaths. Final sample was 36,500 patients with 14 years of median follow-up. For each stage subgroup, the risk of BCSM at 20 years was significantly higher for HR-negative vs HR-positive tumors (IIIA: 49.8% vs 43.2%, P

Background: The risk of breast cancer death persists for at least 20 years from diagnosis. Most reports describing this risk have been based on selected patients (pts) enrolled into clinical trials. These studies report absolute risks at fixed timepoints (i.e. 10 or 20 years) and do not consider the dynamic changes in risks over time. The aim of this study was to develop a tool to calculate residual risks of BCSM and non-BCSM based on individual pt and tumor characteristics, at any given time after breast cancer diagnosis. Methods: Using data from the Surveillance, Epidemiology, and End Results (SEER) program, we identified women diagnosed with non-metastatic invasive breast cancer between 1990-2005, with one primary cancer in their lifetime, and known hormone receptor (HR) status. We estimated the effect of baseline clinical and pathologic variables known to be prognostic, including pt age, HR status, tumor size (T), nodal status (N), and tumor grade, on residual cumulative risks of BCSM and non-BCSM over time. The tool generates the residual death risk (RDR), which is a nonparametric estimate of the cumulative risk of BCSM and non-BCSM by year 20 after any given time from initial diagnosis, among patients defined by baseline clinical and pathologic variables using the method of Gray (1988) implemented in the cmprsk package in R. Results: We included 235,015 pts (median follow-up = 14 years). Among all breast cancer deaths, the proportion occurring after 5 years was 60% for HR+ vs 24% for HR- (p BCSMnon-BCSMAll-cause mortality% Event-FreeCumulative risk (%)Cumulative risk (%)Cumulative risk (%)at 5 yat 10 yy 5-20y 0-20y 0-20y 0-20Nodal status by HR status (any T)HR+N097.293.98.610.633.243.8N192.183.920.025.225.550.8N281.566.236.145.621.266.8N367.749.150.163.116.179.2HR-N089.285.47.317.022.739.7N174.268.312.234.317.051.3N257.049.320.053.514.568.0N340.733.526.268.79.378.0Tumor size among N0 onlyHR+T1a99.097.64.25.030.435.4T1b98.997.25.15.934.440.2T1c97.694.38.710.532.943.3HR-T1a97.394.74.97.323.030.3T1b95.191.96.210.527.137.7T1c91.787.97.514.823.037.8 Citation Format: Jose P Leone, Sara M Tolaney, Bernardo A Leone, Rachel A Freedman, Michael J Hassett, Julieta Leone, Carlos T Vallejo, Eric P Winer, Nancy U Lin, Nabihah Tayob. Population-based tool to estimate residual risks of breast cancer specific mortality (BCSM) and non-BCSM [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS6-13.

Background: Genomic mechanisms associated with response to ICI in mTNBC are largely unknown. The aim of this work is to assess the genomic and immune profiles of mTNBC samples collected from patients (pts) treated with ICI. Methods: We identified 31 women with mTNBC treated with ICI (pembrolizumab, n=6, NCT02447003; atezolizumab, n=4, NCT01375842; nivolumab + cabozantinib, n = 6, NCT03316586; pembrolizumab + eribulin, n=8, NCT02513472; atezolizumab + nab-paclitaxel, n=7, NCT01633970) who had tumor tissue or blood available for sequencing obtained before and after ICI. Clinical benefit (CB), here defined as any objective response or stable disease (SD) for > 24 weeks, was observed in 20 pts (65%). An extraordinary responder was defined as having CB ≥ 2 yrs; 5 pts were considered extraordinary responders (range 26-60months). Whole exome sequencing (WES) was done on each tumor and on germline DNA from blood (23 pts had successful WES performed on samples collected before ICI; 5 of these had WES on samples taken after disease progression). RNA sequencing (RNAseq) was successfully performed in 18 of the tumors with WES performed on samples before ICI; and 3 of these had RNAseq on samples taken after disease progression. 18 pts had tumors assessed by multiplex immunofluorescence (mIF) panels encompassing CD4, CD8, PD-1, PD-L1, and cytokeratin on samples collected before ICI. WES, deep targeted panel and low coverage whole genome sequencing were performed on serially collected plasma samples from 22 pts to evaluate tumor fraction and specific mutations. The association between biomarkers and clinical benefit to ICI was assessed. Results: 21 of 31 pts (67%) had received ≥1 prior lines of systemic therapy in the metastatic setting before starting ICI. Among the most frequently mutated genes at baseline are: TP53 (57%); PIK3CA (18%); DNAH5, MYH8 (both 13%); KMT2C, AKT1, LAMA2 (all 9%). Pts with CB had a higher tumor mutational burden (TMB) than pts with no CB (p=0.018). Differential expression analysis of RNAseq data revealed an upregulation of several immune-related genes in pts with CB, indicating increased immune infiltration in that group. Gene set enrichment analysis of this expression data using hallmark and canonical pathway gene sets from MSigDB (nominal p-val < 0.05) showed that, compared to samples from pts without CB, extraordinary responders had elevated transcriptional signatures of several cancer-related pathways associated with cell survival, proliferation and metabolism, as well as genes associated with increased immune infiltration and upregulation of inflammatory response programs. The mIF showed that the tumor microenvironment (TME) of pts with CB were enriched in Cytokeratin-negative/PD-L1-positive cells compared to those without CB (p=0.014). Expression of CD4, CD8 and PD-1 was not significantly different between pts with and without CB. Genomic analysis of circulating tumor DNA, and tumor evolutionary analysis for pts with both pre- and post-ICI samples (acquired resistance) will be presented. Conclusions: Clinical benefit to ICI in mTNBC was associated with upregulation of immune-related pathways, enrichment of non-tumoral PD-L1-positive cells in TME, and high TMB. Citation Format: Romualdo Barroso-Sousa, Juliet Forman, Zachary T. Weber, Katherine Collier, Katrina Z. Kao, Edward T. Richardson, III, Tanya Keenan, Ofir Cohen, Michael P. Manos, Ryan C. Brennick, Patrick Ott, F. Steve Hodi, Deborah A. Dillon, Nancy U. Lin, Eliezer E. Van Allen, Scott Rodig, Eric P. Winer, Elizabeth A. Mittendorf, Catherine J. Wu, Daniel Stover, Nikhil Wagle, Sachet Shukla, Sara Tolaney. Comprehensive genomic analysis reveals molecular correlates of response to immune checkpoint inhibitors (ICI) in metastatic triple-negative breast cancer (mTNBC) [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS4-25.

Background: In the phase 2 KEYNOTE-086 study (NCT02447003), pembrolizumab monotherapy had durable antitumor activity in a subset of patients with previously treated mTNBC (cohort A; n = 170) and in patients with previously untreated PD-L1-positive mTNBC (cohort B; n = 84). In this exploratory analysis of KEYNOTE-086, we evaluated the association between several biomarkers and response to pembrolizumab. Methods: Cohort A enrolled patients regardless of PD-L1 expression who had documented disease progression following ≥1 systemic therapy for metastatic disease. Cohort B enrolled patients with PD-L1-positive (combined positive score [CPS] ≥1) tumors who had not received prior systemic therapy for metastatic disease. Immunohistochemistry was used to measure PD-L1 CPS and CD8 density; H&E staining for percentage of stromal tumor infiltrating lymphocytes (sTILs); RNA-sequencing for 18-gene T-cell-inflamed gene expression profile (GEP), angiogenesis, and glycolysis signatures; and whole exome sequencing (paired tumor and germline) for TMB (TMB-H defined as ≥175 mut/exome), HRD-LOH (DNA damage), Signature 3, and APOBEC. Biomarkers were analyzed as continuous variables in cohorts A and B combined and individually. Area under the receiver operating characteristic curve was estimated between each biomarker and overall response rate (ORR). Wald test P-values were calculated using logistic regression adjusted for cohort and Eastern Cooperative Oncology Group performance status. Germline and somatic BRCA1/2 mutations were pooled; one-sided P-value was calculated using Fisher’s exact test. Spearman’s correlation was used for correlations. Results: Biomarker data were available in the following number of patients: 253 (99.6%; PD-L1), 204 (80.3%; CD8), 187 (73.6%; GEP), 171 (67.3%; TMB/HRD), 228 (89.8%; sTILs), 163 (64.2%; Signature 3/APOBEC), and 132 (52.0%; angiogenesis/glycolysis). When data from cohorts A and B were combined, PD-L1 CPS (median 2; IQR 0-10), CD8 (median 159; IQR 62-319), GEP (median -0.34; IQR -0.57 to -0.11), TMB (median 82 mut/exome; IQR 50-139), and sTILs (median 5; IQR 2-20) were significantly associated with ORR (Table). There were moderate correlations between PD-L1 and GEP (r = 0.532), PD-L1 and sTILs (r = 0.451), and GEP and sTILs (r = 0.490). No correlation was observed between TMB and PD-L1 (r = 0.038), GEP (r = -0.035), and sTILs (r = -0.031). When cohorts were combined, TMB was significantly associated with ORR, PFS, and OS after adjustment for PD-L1, GEP, CD8, or sTILs. HRD-LOH score, Signature 3, and APOBEC were not significantly associated with ORR (Table); P for BRCA1/2 was 0.2385. The angiogenesis signature was associated with lack of response while the glycolysis signature was associated with response to pembrolizumab (Table). Conclusions: In this exploratory biomarker analysis from KEYNOTE-086, higher levels of PD-L1, GEP, TMB, CD8 IHC, sTILs, and the glycolysis signature were associated with increased response to pembrolizumab monotherapy. These findings may help identify patients with mTNBC who are most likely to respond to pembrolizumab. Table. Association of Biomarkers as Continuous Variables With Pembrolizumab Objective ResponseBiomarkerCombined Cohorts AUCCombined Cohorts P*Combined Cohorts Multitest corrected PCohort A AUCCohort B AUCPD-L10.6740.040-0.5440.654GEP0.7480.003-0.8370.561TMB0.6270.007-0.5480.710CD8 IHC0.760.000020.000120.850.68sTILs0.6710.012-0.6320.641HRD0.3940.874-0.5220.316Signature 30.6830.072-0.6970.736APOBEC0.5280.537-0.6740.623Angiogenesis0.6770.0090.0450.6610.731Glycolysis0.6120.0090.0360.8590.459AUC, area under the curve.*One-sided P-values are shown for all biomarkers except for Signature 3 and APOBEC, for which 2-sided P-values are shown. Citation Format: Sherene Loi, Peter Schmid, Javier Cortes, David W. Cescon, Eric P. Winer, Deborah L. Toppmeyer, Hope S. Rugo, Michelino De Laurentiis, Rita Nanda, Hiroji Iwata, Ahmad Awada, Antoinette R. Tan, Roberto Salgado, Vassiliki Karantza, Petar Jelinic, Anran Wang, Lingkang Huang, Razvan Cristescu, Lakshman Annamalai, Jennifer Yearley, Jennifer Yearley, Sylvia Adams. Association between biomarkers and response to pembrolizumab in patients with metastatic triple-negative breast cancer (mTNBC): Exploratory analysis from KEYNOTE-086 [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PD14-07.

Purpose: In contrast to recurrence after initial diagnosis of stage I–III breast cancer [recurrent metastatic breast cancer (rMBC)], de novo metastatic breast cancer (dnMBC) represents a unique setting to elucidate metastatic drivers in the absence of treatment selection. We present the genomic landscape of dnMBC and association with overall survival (OS). Experimental Design: Targeted DNA sequencing (OncoPanel) was prospectively performed on either primary or metastatic tumors from 926 patients (212 dnMBC and 714 rMBC). Single-nucleotide variants, copy-number variations, and tumor mutational burden (TMB) in treatment-naïve dnMBC primary tumors were compared with primary tumors in patients who ultimately developed rMBC, and correlated with OS across all dnMBC. Results: When comparing primary tumors by subtype, MYB amplification was enriched in triple-negative dnMBC versus rMBC (21.1% vs. 0%, P = 0.0005, q = 0.111). Mutations in KMTD2, SETD2, and PIK3CA were more prevalent, and TP53 and BRCA1 less prevalent, in primary HR+/HER2− tumors of dnMBC versus rMBC, though not significant after multiple comparison adjustment. Alterations associated with shorter OS in dnMBC included TP53 (wild-type: 79.7 months; altered: 44.2 months; P = 0.008, q = 0.107), MYC (79.7 vs. 23.3 months; P = 0.0003, q = 0.011), and cell-cycle (122.7 vs. 54.9 months; P = 0.034, q = 0.245) pathway genes. High TMB correlated with better OS in triple-negative dnMBC (P = 0.041). Conclusions: Genomic differences between treatment-naïve dnMBC and primary tumors of patients who developed rMBC may provide insight into mechanisms underlying metastatic potential and differential therapeutic sensitivity in dnMBC. Alterations associated with poor OS in dnMBC highlight the need for novel approaches to overcome potential intrinsic resistance to current treatments.

Background Understanding the impact of the tumor immune microenvironment and BRCA1/2-related DNA repair deficiencies on the clinical activity of immune checkpoint inhibitors may help optimize both patient and treatment selection in metastatic triple-negative breast cancer. In this substudy from the phase 3 IMpassion130 trial, immune biomarkers and BRCA1/2 alterations were evaluated for association with clinical benefit with atezolizumab and nab-paclitaxel (A+nP) vs placebo and nP in unresectable (P+nP) locally advanced or metastatic triple-negative breast cancer. Methods Patients were randomly assigned 1:1 to nab-paclitaxel 100 mg/m2 (days 1, 8, and 15 of a 28-day cycle) and atezolizumab 840 mg every 2 weeks or placebo until progression or toxicity. Progression-free survival and overall survival were evaluated based on programmed death-ligand 1 (PD-L1) expression on immune cells (IC) and tumor cells, intratumoral CD8, stromal tumor-infiltrating lymphocytes, and BRCA1/2 mutations. Results PD-L1 IC+ in either primary or metastatic tumor tissue was linked to progression-free survival and overall survival benefit with A+nP. PD-L1 IC+ low (26.9%; 243 of 902 patients) and high (13.9%; 125 of 902 patients) populations had improved outcomes that were comparable. Intratumoral CD8 and stromal tumor-infiltrating lymphocytes positivity (sTIL+) were associated with PD-L1 IC+ status; improved outcomes were observed with A+nP vs P+nP only in CD8+ and sTIL+ patients who were also PD-L1 IC+. BRCA1/2 mutations (occurring in 14.5% [89 of 612 patients]) were not associated with PD-L1 IC status, and PD-L1 IC+ patients benefited from A+nP regardless of BRCA1/2 mutation status. Conclusions Although A+nP was more efficacious in patients with richer tumor immune microenvironment, clinical benefit was only observed in patients whose tumors were PD-L1 IC+.

Summary Background Palbociclib added to endocrine therapy improves progression-free survival in hormone-receptor-positive, HER2-negative, metastatic breast cancer. The PALLAS trial aimed to investigate whether the addition of 2 years of palbociclib to adjuvant endocrine therapy improves invasive disease-free survival over endocrine therapy alone in patients with hormone-receptor-positive, HER2-negative, early-stage breast cancer. Methods PALLAS is an ongoing multicentre, open-label, randomised, phase 3 study that enrolled patients at 406 cancer centres in 21 countries worldwide with stage II–III histologically confirmed hormone-receptor-positive, HER2-negative breast cancer, within 12 months of initial diagnosis. Eligible patients were aged 18 years or older with an Eastern Cooperative Oncology Group performance score of 0 or 1. Patients were randomly assigned (1:1) in permuted blocks of random size (4 or 6), stratified by anatomic stage, previous chemotherapy, age, and geographical region, by use of central telephone-based and web-based interactive response technology, to receive either 2 years of palbociclib (125 mg orally once daily on days 1–21 of a 28-day cycle) with ongoing standard provider or patient-choice adjuvant endocrine therapy (tamoxifen or aromatase inhibitor, with or without concurrent luteinising hormone-releasing hormone agonist), or endocrine therapy alone, without masking. The primary endpoint of the study was invasive disease-free survival in the intention-to-treat population. Safety was assessed in all randomly assigned patients who started palbociclib or endocrine therapy. This report presents results from the second pre-planned interim analysis triggered on Jan 9, 2020, when 67% of the total number of expected invasive disease-free survival events had been observed. The trial is registered with ClinicalTrials.gov (NCT02513394) and EudraCT (2014-005181-30). Findings Between Sept 1, 2015, and Nov 30, 2018, 5760 patients were randomly assigned to receive palbociclib plus endocrine therapy (n=2883) or endocrine therapy alone (n=2877). At the time of the planned second interim analysis, at a median follow-up of 23·7 months (IQR 16·9–29·2), 170 of 2883 patients assigned to palbociclib plus endocrine therapy and 181 of 2877 assigned to endocrine therapy alone had invasive disease-free survival events. 3-year invasive disease-free survival was 88·2% (95% CI 85·2–90·6) for palbociclib plus endocrine therapy and 88·5% (85·8–90·7) for endocrine therapy alone (hazard ratio 0·93 [95% CI 0·76–1·15]; log-rank p=0·51). As the test statistic comparing invasive disease-free survival between groups crossed the prespecified futility boundary, the independent data monitoring committee recommended discontinuation of palbociclib in patients still receiving palbociclib and endocrine therapy. The most common grade 3–4 adverse events were neutropenia (1742 [61·3%] of 2840 patients on palbociclib and endocrine therapy vs 11 [0·3%] of 2903 on endocrine therapy alone), leucopenia (857 [30·2%] vs three [0·1%]), and fatigue (60 [2·1%] vs ten [0·3%]). Serious adverse events occurred in 351 (12·4%) of 2840 patients on palbociclib plus endocrine therapy versus 220 (7·6%) of 2903 patients on endocrine therapy alone. There were no treatment-related deaths. Interpretation At the planned second interim analysis, addition of 2 years of adjuvant palbociclib to adjuvant endocrine therapy did not improve invasive disease-free survival compared with adjuvant endocrine therapy alone. On the basis of these findings, this regimen cannot be recommended in the adjuvant setting. Long-term follow-up of the PALLAS population and correlative studies are ongoing. Funding Pfizer.

PURPOSE CALGB 40601 assessed whether dual versus single human epidermal growth factor receptor 2 (HER2) –targeting drugs added to neoadjuvant chemotherapy increased pathologic complete response (pCR). Here, we report relapse-free survival (RFS), overall survival (OS), and gene expression signatures that predict pCR and survival. PATIENTS AND METHODS Three hundred five women with untreated stage II and III HER2-positive breast cancer were randomly assigned to receive weekly paclitaxel combined with trastuzumab plus lapatinib (THL), trastuzumab (TH), or lapatinib (TL). The primary end point was pCR, and secondary end points included RFS, OS, and gene expression analyses. mRNA sequencing was performed on 264 pretreatment samples. RESULTS One hundred eighteen patients were randomly allocated to THL, 120 to TH, and 67 to TL. At more than 7 years of follow-up, THL had significantly better RFS and OS than did TH (RFS hazard ratio, 0.32; 95% CI, 0.14 to 0.71; P = .005; OS hazard ratio, 0.34; 95% CI, 0.12 to 0.94; P = .037), with no difference between TH and TL. Of 688 previously described gene expression signatures, significant associations were found in 215 with pCR, 45 with RFS, and only 22 with both pCR and RFS (3.2%). Specifically, eight immune signatures were significantly correlated with a higher pCR rate and better RFS. Among patients with residual disease, the immunoglobulin G signature was an independent, good prognostic factor, whereas the HER2-enriched signature, which was associated with a higher pCR rate, showed a significantly shorter RFS. CONCLUSION In CALGB 40601, dual HER2-targeting resulted in significant RFS and OS benefits. Integration of intrinsic subtype and immune signatures allowed for the prediction of pCR and RFS, both overall and within the residual disease group. These approaches may provide means for rational escalation and de-escalation treatment strategies in HER2-positive breast cancer.

Purpose: To determine whether the androgen receptor (AR) inhibitor, enzalutamide, improves effectiveness of endocrine therapy (ET) in hormone receptor–positive (HR+) breast cancer. Patients and Methods: In this phase II trial, patients with HR+/HER2 normal advanced/metastatic breast cancer were randomized 1:1 to exemestane 25 mg with placebo or exemestane 50 mg with enzalutamide 160 mg daily (NCT02007512). Two parallel cohorts enrolled patients with 0 (cohort 1) or 1 (cohort 2) prior ET for advanced disease. Progression-free survival (PFS) was the primary endpoint in the intent-to-treat (ITT) population of each cohort. Biomarkers were evaluated in an exploratory analysis. Results: Overall, 247 patients were randomized (cohort 1, n = 127 and cohort 2, n = 120). PFS was not improved in either cohort of the ITT population [HR, 0.82 (95% confidence interval (CI), 0.54–1.26); P = 0.3631 for cohort 1 and HR, 1.02 (95% CI, 0.66–1.59); P = 0.9212 for cohort 2]. In cohort 1, high levels of AR mRNA were associated with greater benefit of enzalutamide (Pinteraction = 0.0048). This effect was particularly apparent in patients with both high levels of AR mRNA and low levels of ESR1 mRNA [HR, 0.24 (95% CI, 0.10–0.60); P = 0.0011]. The most common any grade adverse events in the enzalutamide arms were nausea (39%) in cohort 1 and fatigue (37%) in cohort 2. Conclusions: Enzalutamide with exemestane was well tolerated. While PFS was not improved by the addition of enzalutamide to exemestane in an unselected population, ET-naïve patients with high AR mRNA levels, particularly in combination with low ESR1 mRNA levels, may benefit from enzalutamide with exemestane.

An important challenge in the field of cancer is finding the balance between delivering effective treatments and avoiding adverse effects and financial toxicity caused by innovative, yet expensive, drugs. To address this, several treatment de-escalation trials have been conducted, but only a few of these have provided clear answers. A few trials had poor accrual or had design flaws that led to conflicting results. Members of the Breast International Group (BIG) and North American Breast Cancer Group (NABCG) believe the way forward is to understand the lessons from these trials and listen more carefully to what truly matters to our patients. We reviewed several adjuvant trials of different cancer types and developed a road map for improving the design and implementation of future de-escalation trials. The road map incorporates patients’ insights obtained through focused group discussions across the BIG-NABCG networks. Considerations for the development of de-escalation trials for systemic adjuvant treatment, including noninferiority trial design, choice of end points, and prioritization of a patient’s perspectives, are presented in this consensus article.

PARP inhibitors (PARPi) have drastically changed the treatment landscape of advanced ovarian tumors withBRCAmutations. However, the impact of this class of inhibitors in patients with advancedBRCA-mutant breast cancer is relatively modest. Using a syngeneic genetically-engineered mouse model of breast tumor driven byBrca1deficiency, we show that tumor-associated macrophages (TAMs) blunt PARPi efficacy both in vivo and in vitro. Mechanistically, BRCA1-deficient breast tumor cells induce pro-tumor polarization of TAMs, which in turn suppress PARPi-elicited DNA damage in tumor cells, leading to reduced production of dsDNA fragments and synthetic lethality, hence impairing STING-dependent anti-tumor immunity. STING agonists reprogram M2-like pro-tumor macrophages into an M1-like anti-tumor state in a macrophage STING-dependent manner. Systemic administration of a STING agonist breaches multiple layers of tumor cell-mediated suppression of immune cells, and synergizes with PARPi to suppress tumor growth. The therapeutic benefits of this combination require host STING and are mediated by a type I IFN response and CD8+T cells, but do not rely on tumor cell-intrinsic STING. Our data illustrate the importance of targeting innate immune suppression to facilitate PARPi-mediated engagement of anti-tumor immunity in breast cancer.

The risk of breast cancer-specific mortality (BCSM) persists for at least 20 years from diagnosis. Estimating the risk of BCSM over this extended period along with competing risks of death would aid clinical decision-making. We aimed to develop an interactive tool called 'ESTIMATE', to explore the Surveillance, Epidemiology, and End Results (SEER) registry to quantify residual risks of BCSM, non-BCSM and all-cause mortality in non-metastatic, hormone receptor (HR)-positive breast cancer patient subgroups at any given time after diagnosis, up to 20 years.Using SEER data, we included 264,237 women with invasive, non-metastatic, HR-positive breast cancer diagnosed from 1990 to 2006. We developed a tool that provides a nonparametric estimate of the residual cumulative risk of BCSM and non-BCSM by year 20 after any specified time from initial diagnosis, among patients defined by baseline clinical and pathologic variables, using Gray's subdistribution method.ESTIMATE allows the user to input patient and tumour characteristics and the preferred timeframe. For example, patients in the age group of 40-49 diagnosed with T1cN1, grade II breast cancer who survived 7 years, have a 14% (95% confidence interval [CI]: 11.9%-16.1%) residual cumulative risk of BCSM in the next 13 years, and a 6.4% (95% CI: 4.7%-8.1%) residual cumulative risk of non-BCSM over the same period.ESTIMATE provides population-based risks of BCSM, non-BCSM and all-cause mortality through 20 years after diagnosis of HR-positive breast cancer, based on patient and tumour characteristics. ESTIMATE can inform discussions about prognosis, a balance between competing risks and aid clinical decision-making.

Purpose:To identify clinically relevant mechanisms of resistance to ER-directed therapies in ER+ breast cancer.Experimental Design:We conducted a genome-scale functional screen spanning 10,135 genes to investigate genes whose overexpression confer resistance to selective estrogen receptor degraders. In parallel, we performed whole-exome sequencing in paired pretreatment and postresistance biopsies from 60 patients with ER+ metastatic breast cancer who had developed resistance to ER-targeted therapy. Furthermore, we performed experiments to validate resistance genes/pathways and to identify drug combinations to overcome resistance.Results:Pathway analysis of candidate resistance genes demonstrated that the FGFR, ERBB, insulin receptor, and MAPK pathways represented key modalities of resistance. The FGFR pathway was altered via FGFR1, FGFR2, or FGF3 amplifications or FGFR2 mutations in 24 (40%) of the postresistance biopsies. In 12 of the 24 postresistance tumors exhibiting FGFR/FGF alterations, these alterations were acquired or enriched under the selective pressure of ER-directed therapy. In vitro experiments in ER+ breast cancer cells confirmed that FGFR/FGF alterations led to fulvestrant resistance as well as cross-resistance to the CDK4/6 inhibitor palbociclib. RNA sequencing of resistant cell lines demonstrated that FGFR/FGF induced resistance through ER reprogramming and activation of the MAPK pathway. The resistance phenotypes were reversed by FGFR inhibitors, a MEK inhibitor, and/or a SHP2 inhibitor.Conclusions:Our results suggest that FGFR pathway is a distinct mechanism of acquired resistance to ER-directed therapy that can be overcome by FGFR and/or MAPK pathway inhibitors.

The 21-gene Breast Recurrence Score test predicts benefit from adjuvant chemotherapy in estrogen receptor-positive, HER2-negative (ER+/HER2−) breast cancer (BC). We examined whether the 21-gene assay predicts response to neoadjuvant chemotherapy (NCT). We identified patients with stage I–III ER+/HER2− BC treated with NCT from the Young Women’s Breast Cancer Study, a prospective cohort of women diagnosed with BC at age ≤40 years. The 21-gene assay was performed on tumor specimens removed prior to NCT either as part of clinical care or retrospectively for research. Pathological complete response (pCR) was defined as ypT0/is ypN0. The relationship between Recurrence Score result and pCR was evaluated using logistic regression modeling. 76 women received NCT for ER+/HER2− BC and were eligible for this analysis. Median age at diagnosis was 37 years (range 24–40). Scores ranged between 5 and 77 with 50% >25 and 5% 25 was 21% (8/38) vs. 5% in patients with scores

In 2016, we initiated standardized “reflex” Oncotype DX Recurrence Score (RS) testing for patients ≤ 65 years with pT1-2N0-1 HR+/HER2− breast cancer. Here, we examine RS testing patterns, RS distribution, and factors associated with chemotherapy use in patients with pN1 breast cancer. Patients with stage I–III HR+/HER2− pN1 breast cancer treated with upfront surgery from February 2016 to March 2019 were identified. Clinical characteristics were compared between patients meeting reflex RS testing criteria, those with RS ordered outside of reflex criteria, and those without RS testing. RS was categorized as low (

Background Brain metastases are frequent in HER2-positive breast cancer. ONT-380 (tucatinib) is a potent selective inhibitor of HER2 with intracranial activity in preclinical models. Patients and methods This was a phase I study of tucatinib with trastuzumab, without chemotherapy, in patients with progressive, measurable HER2-positive brain metastases. The study tested two schedules of tucatinib: cohort A was twice daily and cohort B was once daily. The primary objective was determination of the maximum tolerated dose (MTD). Secondary end points included objective response (intracranial and extracranial) using modified RECIST and clinical benefit rate (CBR). Results Overall, 41 patients were enrolled (cohort A, n = 22; cohort B, n = 19). Patients had a median of two prior treatments for metastatic breast cancer and 83% had progressed after prior brain radiation. The MTD of tucatinib for cohort A was 300 mg twice daily and for cohort B was 750 mg once daily. The most common dose-limiting toxicities included thrombocytopenia and aspartate transaminase/alanine aminotransferase elevation. Grade 3/4 aspartate transaminase/alanine aminotransferase elevation occurred in nine of 41 patients (22%). Intracranial responses were observed in two of 17 (12%) patients in cohort A and one of 17 (6%) patients in cohort B treated at the MTD. In cohort A, CBR at 16 weeks was 35% (n = 6). In cohort B, CBR at 16 weeks was 53% (n = 9). Of 15 patients overall who experienced clinical benefit, 12 (80%) had received prior neratinib and/or lapatinib. Median progression-free survival for cohorts A and B was 3.4 and 4.1 months, respectively. Conclusion The combination of tucatinib and trastuzumab is tolerable and demonstrated preliminary evidence of efficacy in patients with HER2-positive brain metastases. Clinical Trial Registration NCT01921335.

Mechanisms driving resistance to cyclin-dependent kinase 4/6 inhibitors (CDK4/6i) in hormone receptor–positive (HR+) breast cancer have not been clearly defined. Whole-exome sequencing of 59 tumors with CDK4/6i exposure revealed multiple candidate resistance mechanisms including RB1 loss, activating alterations in AKT1, RAS, AURKA, CCNE2, ERBB2, and FGFR2, and loss of estrogen receptor expression. In vitro experiments confirmed that these alterations conferred CDK4/6i resistance. Cancer cells cultured to resistance with CDK4/6i also acquired RB1, KRAS, AURKA, or CCNE2 alterations, which conferred sensitivity to AURKA, ERK, or CHEK1 inhibition. Three of these activating alterations—in AKT1, RAS, and AURKA—have not, to our knowledge, been previously demonstrated as mechanisms of resistance to CDK4/6i in breast cancer preclinically or in patient samples. Together, these eight mechanisms were present in 66% of resistant tumors profiled and may define therapeutic opportunities in patients.Significance:We identified eight distinct mechanisms of resistance to CDK4/6i present in 66% of resistant tumors profiled. Most of these have a therapeutic strategy to overcome or prevent resistance in these tumors. Taken together, these findings have critical implications related to the potential utility of precision-based approaches to overcome resistance in many patients with HR+ metastatic breast cancer.This article is highlighted in the In This Issue feature, p. 1079

PURPOSE The use of growth factors adds considerable expense and some toxicity to adjuvant breast cancer chemotherapy. We tested the feasibility and safety of omitting routine peg-filgrastim use during the paclitaxel portion of the dose-dense doxorubicin-cyclophosphamide–paclitaxel regimen. PATIENTS AND METHODS This was a prospective, single-arm study in which patients 18 to 65 years of age who completed 4 cycles of dose-dense doxorubicin-cyclophosphamide for stage I-III breast cancer received paclitaxel 175 mg/m2 every 2 weeks. Peg-filgrastim was administered after paclitaxel only if patients had had febrile neutropenia in a prior cycle or at investigator discretion if patients had infections or treatment delays of > 1 week. Once a patient received peg-filgrastim, it was administered in all future cycles. The primary end point was the rate of paclitaxel completion within 7 weeks from cycle 1 day 1 to cycle 4 day 1. If ≥ 100 out of 125 patients completed 4 cycles of paclitaxel without dose delay, the regimen would be considered feasible. RESULTS The enrollment goal of 125 patients was met. Median age was 46 years (range, 21-65 years), and 112 patients (90% [95% CI, 83% to 94%]) completed dose-dense paclitaxel within 7 weeks. Omission of peg-filgrastim was not causally related to noncompletion of paclitaxel in any patients. The most common reasons for dose reduction or delays were nonhematologic. One patient experienced febrile neutropenia but was able to complete paclitaxel on time. Eight patients (6.4%) received peg-filgrastim during the trial. Overall, peg-filgrastim was administered in only 4.3% of paclitaxel cycles. CONCLUSION Omission of routine peg-filgrastim during dose-dense paclitaxel according to a prespecified algorithm seems to be safe and feasible and was associated with a 95.7% reduction in the use of peg-filgrastim relative to the current standard of care.

PURPOSE Platinum compounds have activity in triple-negative breast cancer (TNBC) in germline BRCA mutation carriers ( BRCA carriers). Limited data exist for estrogen receptor (ER)–positive (+) breast cancer among BRCA carriers. INFORM is a randomized, multicenter, phase II trial comparing pathologic complete response (pCR) rates (ypT0/is, N0) after neoadjuvant single-agent cisplatin (CDDP) versus doxorubicin-cyclophosphamide (AC) in BRCA carriers with stage I-III human epidermal growth factor receptor 2 (HER2)–negative breast cancer. Secondary objectives included residual cancer burden scores (RCB) of 0 or 1 (combined) and toxicity. The goal was to determine whether pCR was ≥ 20% higher with CDDP than AC. PATIENTS AND METHODS BRCA carriers with cT1-3 (≥ 1.5 cm), cN0-3 HER2-negative breast cancer were randomly assigned to preoperative CDDP (75 mg/m2 every 3 weeks × 4 doses) or AC (doxorubicin 60 mg/m2; cyclophosphamide 600 mg/m2 every 2-3 weeks × 4 doses) followed by surgery. Pathologic responses were confirmed by central review. RESULTS A total of 118 patients were randomly assigned; 117 were included in outcome analyses. Mean age was 42 years (range, 24-73 years); 69% were BRCA1+, 30% were BRCA2+, and 2% had both mutations. Clinical stage was I for 19%, II for 63%, and III for 18%; 45% had nodal involvement at baseline. Seventy percent had TNBC. Clinical and tumor characteristics were well matched between treatment arms. The pCR rate was 18% with CDDP and 26% with AC, yielding a risk ratio (RR) of 0.70 (90% CI, 0.39 to 1.2). The risk of RCB 0 or 1 (RCB 0/1) was 33% with CDDP and 46% with AC (RR, 0.73; 90% CI, 0.50 to 1.1). Both regimens were generally well tolerated without unexpected toxicities. CONCLUSION pCR or RCB 0/1 is not significantly higher with CDDP than with AC in BRCA carriers with stage I-III HER2-negative breast cancer for both TNBC and ER+/HER2-negative disease.

PURPOSE In the HER2CLIMB study, patients with human epidermal growth factor receptor 2 (HER2)–positive breast cancer with brain metastases (BMs) showed statistically significant improvement in progression-free survival (PFS) with tucatinib. We describe exploratory analyses of intracranial efficacy and survival in participants with BMs. PATIENTS AND METHODS Patients were randomly assigned 2:1 to tucatinib or placebo, in combination with trastuzumab and capecitabine. All patients underwent baseline brain magnetic resonance imaging; those with BMs were classified as active or stable. Efficacy analyses were performed by applying RECIST 1.1 criteria to CNS target lesions by investigator assessment. CNS-PFS (intracranial progression or death) and overall survival (OS) were evaluated in all patients with BMs. Confirmed intracranial objective response rate (ORR-IC) was evaluated in patients with measurable intracranial disease. RESULTS There were 291 patients with BMs: 198 (48%) in the tucatinib arm and 93 (46%) in the control arm. The risk of intracranial progression or death was reduced by 68% in the tucatinib arm (hazard ratio [HR], 0.32; 95% CI, 0.22 to 0.48; P < .0001). Median CNS-PFS was 9.9 months in the tucatinib arm versus 4.2 months in the control arm. Risk of death was reduced by 42% in the tucatinib arm (OS HR, 0.58; 95% CI, 0.40 to 0.85; P = .005). Median OS was 18.1 versus 12.0 months. ORR-IC was higher in the tucatinib arm (47.3%; 95% CI, 33.7% to 61.2%) versus the control arm (20.0%; 95% CI, 5.7% to 43.7%; P = .03). CONCLUSION In patients with HER2-positive breast cancer with BMs, the addition of tucatinib to trastuzumab and capecitabine doubled ORR-IC, reduced risk of intracranial progression or death by two thirds, and reduced risk of death by nearly half. To our knowledge, this is the first regimen to demonstrate improved antitumor activity against BMs in patients with HER2-positive breast cancer in a randomized, controlled trial.

BackgroundHigh tumor mutation burden (TMB) has been associated with benefit to immunotherapy in multiple tumor types. However, the prevalence of hypermutated breast cancer is not well described. The aim of this study is to evaluate frequency, mutational patterns, and genomic profile of hypermutated breast cancer.Patients and MethodsWe used de-identified data from individuals with primary or metastatic breast cancer from six different publicly available genomic studies. The prevalence of hypermutated breast cancer was determined among 3969 patients’ samples that underwent whole exome sequencing or gene panel sequencing. Samples were classified as having high TMB if they had ≥10 mutations per megabase (mut/Mb). An additional 8 patients were identified from a Dana-Farber Cancer Institute cohort for inclusion in the hypermutated cohort. Among patients with high TMB, the mutational patterns, and genomic profile were determined. A subset of patients was treated with regimens containing PD-1 inhibitors.ResultsThe median TMB was 2.63 mut/Mb. Median TMB significantly varied according to tumor subtype (HR-/HER2-> HER2+ > HR+/HER2-,p< 0.05) and sample type (metastatic > primary,p2.2×10−16). Hypermutated tumors were found in 198 patients (5%), with an enrichment in metastatic versus primary tumors (8.4% versus 2.9%, p = 6.5 × 10−14). APOBEC activity (59.2%), followed by mismatch repair deficiency (MMRd; 36.4%), were the most common mutational processes among hypermutated tumors. Three patients with hypermutated breast cancer—including two with a dominant APOBEC activity signature and one with a dominant MMRd signature—treated with pembrolizumab-based therapies derived an objective and durable response to therapy.ConclusionHypermutation occurs in 5% of all breast cancers, with an enrichment in metastatic tumors. Different mutational signatures are present in this population, with APOBEC activity being the most common dominant process. Preliminary data suggest that hypermutated breast cancers are more likely to benefit from PD-1 inhibitors.Key MessageHigh tumor mutation burden is found in 5% of all breast cancers and is more common in metastatic tumors. While different mutational signatures are present in hypermutated tumors, APOBEC activity is the most common dominant process. Preliminary data suggest that those tumors are more likely to benefit from PD-1 inhibitors.

Background: Recent studies in murine models and humans suggest that modulation of the gut microbiome may enhance response to immune checkpoint blockade in different cancer types. However, little is known about the landscape of gut microbiome in pts with HR+ MBC and its influence on response to chemotherapy and immunotherapy.Methods: A randomized phase 2 trial of E +/- P for pts with HR+ MBC (n= 88) was conducted. The results of this study have been previously presented and found the addition of P did not result in an improvement in progression-free survival (PFS). Fecal samples were prospectively collected (baseline (BL), after 2 cycles of therapy (C2), and end of treatment (EOT)) in a subset of pts (E+P, n = 12; E, n = 11) in order to evaluate if microbiome was associated with response (partial response [PR], stable disease [SD], and progressive disease [PD]), PFS, and overall survival (OS). 16S rRNA gene sequencing was performed to characterize the diversity and composition of fecal microbiome. Results: A total 23 pts provided 23 BL, 22 C2, and 5 EOT fecal specimens for microbiome profiling. 16S(v3-4) rRNA gene data was successfully generated for all samples and the dataset was rarefied to 24,743 reads for analysis. Overall, the variability in the composition and structure of the fecal microbiome was significantly driven by each individual (p Conclusion: The composition and structure of the fecal microbiome identified in this study were found to be associated primarily with the pt rather than with any of the variables studied including type of treatment and outcome. Although the fecal microbiome from all pts randomized were indistinguishable at BL, shifts in the abundance of certain types of bacteria like Faecalibacterium and Akkermansia were observed from BL to C2. These shifts were characteristic of pts receiving E but not of those receiving E+P. Although this study is limited by the small sample size in each arm, these findings warrant further evaluation in a larger population to interrogate if the composition and metabolic potential of the fecal microbiome can be used as a predictor of benefit to treatment. Citation Format: Romualdo Barroso de Sousa, Nadim Ajami, Tanya E Keenan, Chelsea Andrews, Jessica L Pittenger, Gerburg Wulf, Laura Spring, Ian E Krop, Eric P Winer, Elizabeth A Mittendorf, Sara M Tolaney. Fecal microbiome and association with outcomes among patients (pts) receiving eribulin (E) +/- pembrolizumab (P) for hormone receptor positive (HR+) metastatic breast cancer (MBC) [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P3-09-16.

Introduction: mTNBC progresses rapidly on first-line chemotherapy. For instance, in the TNT trial, median progression-free survival (PFS) was 3 months on first-line carboplatin. Selective inhibition of Wee1, a negative regulator of the G2 cell cycle checkpoint, may enhance the efficacy of DNA-damaging agents by reducing DNA damage repair. We report the results of the first phase II study assessing the efficacy of the Wee1 inhibitor adavosertib (AZD-1775) with cisplatin in mTNBC. Methods: mTNBC patients (pts) with 0-1 prior lines of chemotherapy in the metastatic setting were eligible. Pts received cisplatin 75 mg/m2 IV followed by combination therapy 21 d later with cisplatin plus adavosertib 200 mg oral twice daily x 5 doses over 2.5 d every 21 d. Tumor biopsies were mandatory for patients with safely accessible tumors, and occurred 5-48 h after monotherapy and 5-8 h after the last adavosertib dose in the first combination therapy cycle. The study used a Simon optimal two-stage design that had 90% power to detect the difference between null (20%) and alternative (40%) response rates with a one-sided type I error of 0.1. The primary endpoint was objective response rate (ORR): an ORR > 30% would identify the regimen as worthy of further study. Key secondary endpoints were PFS and overall survival (OS). Exploratory analyses evaluated the association of response, defined as clinical benefit rate (CBR) > 6 months (CR + PR + SD > 6 mos), with transcriptional and immunostaining profiles of on-treatment tumors (n = 16), as well as with targeted panel genomic alterations in archival tissue. Tumor immune cell composition was assessed by CIBERSORT. Results: 34 pts initiated protocol therapy; median age was 56 yrs, 2 (6%) pts had known BRCA2 mutations, and 14 (41%) had 1 prior line of chemotherapy. Median follow-up was 13 mos. ORR was 29% (3 CR + 7 PR), median PFS 4.9 months (95% CI, 2.3-5.8 mos), CBR 35%, and preliminary OS 14.0 mos (95% CI, 11.8-21.8 mos). All-cause AEs occurred in 100% of pts (G3-4, 56%; most commonly diarrhea, 21%), including one death due to sepsis possibly related to study therapy. The primary tumor of the longest responding patient had a possible biallelic loss-of-function alteration (missense mutation and loss of heterozygosity) in the homologous recombination-related gene FANCM. In Hallmark gene set enrichment analyses of 26 on-treatment biopsies across 16 pts, responding tumors (n = 4) demonstrated enriched expression of immune response gene sets (allograft rejection FDR q < 0.001, IL2-STAT5 signaling FDR q = 0.001, inflammatory response FDR q = 0.003), while non-responding tumors (n = 12) showed enrichment of cell cycle gene sets (E2F targets FDR q < 0.001, G2M checkpoint FDR q < 0.001). In the same on-treatment biopsies, responding tumors (n = 4) had higher tumor infiltrating lymphocytes (46% v. 29%, Mann-Whitney p = 0.04) and lower M0 macrophages (3% v. 17%, Mann-Whitney p = 0.04) than non-responding tumors (n =12). Updated data, including OS and tissue immunostaining results, will be presented. Conclusions: Among mTNBC pts, the combination of adavosertib and cisplatin was associated with a 29% ORR, failing to meet the pre-determined ORR of > 30% required to support further investigation. Responses were associated with immune-related gene expression and TILs detected by RNA sequencing. Citation Format: Tanya E. Keenan, Zhenying Tan-Wasielewski, Lorenzo Trippa, Bose Kochupurakkal, Jennifer L. Guerriero, Rie K. Tahara, Grace Winship, Wafa Osmani, Chelsea Andrews, Jake R. Conway, Meng X He, Ricardo Pastorello, Adam Tracy, Robert E. Godin, Beth A. Overmoyer, Eric P. Winer, Elizabeth A. Mittendorf, Geoffrey I Shapiro, Eliezer M Van Allen, Sara M Tolaney. A phase II study of cisplatin and the Wee1 inhibitor adavosertib in metastatic triple-negative breast cancer (mTNBC) [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P3-10-08.

Background: For patients (pts) with HR+ /HER2- MBC, the optimal regimen following disease progression on the combination of a CDK4/6i plus endocrine therapy (ET) is unknown, and there is a need to evaluate whether continued CDK 4/6 blockade is beneficial in subsequent lines of therapy. Methods: We developed an investigator initiated Phase I/II, open-label trial (NCT02871791) of triplet therapy: palbociclib (PALBO; CDK4/6i) + everolimus (EVE; mTOR inhibitor) + exemestane (EXE; ET) in men or postmenopausal women with measurable HR+ /HER2− MBC who had progressed on prior CDK4/6i and a non-steroidal aromatase inhibitor (NSAI). Pts may have received any number of prior lines of ET, and 0-1 prior line of chemotherapy. Exclusion criteria included prior use of mTORi or EXE. The primary objective was to estimate efficacy of the combination, defined as the clinical benefit rate (CR+PR+SD>6mo). With a one-sided alpha of 0.1, the study had 90% power to detect an improvement in CBR from 40% to 65%. The phase I determined RP2D to be PALBO 100 mg/day (21 of 28 days) + EVE 5mg/day + EXE 25mg/day (previously presented). For pts who entered into the phase IIa part of the study, a research biopsy at baseline and serial research blood collection for circulating tumor DNA (ctDNA) analysis were mandatory. The tumor tissue underwent whole exome sequencing and RNA sequencing and the ctDNA underwent whole exome sequencing. Here we present the first results of the phase 2 study of this triplet regimen. Results: As of June 29, 2019, after a median follow up of 3.8 (2.8-6.2) months, 32 patients were evaluable in the phase II portion of the study. The triplet combination was associated with a clinical benefit rate of 12.5% (n=4), which did not meet the predefined primary endpoint threshold (65%). There were no objective responses achieved. The median PFS was 3.8 (95%CI: 2.0-8.4) months and the 1-year PFS was 16.1% (95%CI: 3.1%-38.0%). The most common AEs were mucositis (all grades, 87.5%; grade 3/4, 15.6%), neutropenia (all grades 84.4%; grade 3/4, 71.9%), and fatigue (all grades 53.1%; grade 3/4, 0%). Data regarding genomic alterations and its association with outcomes will be presented. Conclusions: Among patients with metastatic HR+/HER2- MBC who had previous progression on a NSAI and a CDK 4/6i, there did not appear to be benefit from the addition of PALBO to EXE and EVE, but there were added toxicities. These findings suggest further evaluation of this triplet combination in patients with CDK 4/6i resistance is not warranted. Genomic data from baseline biopsies and circulating tumor DNA will be presented and may help us to explain why patients included in this study were intrinsically resistant to the triplet. Citation Format: Romualdo Barroso-Sousa, Tianyu Li, Lorenzo Trippa, Rebecca Rees, Chelsea Andrews, Arlindo R Ferreira, Karla Helvie, Ann H Partridge, Beth Overmoyer, Eric P Winer, Nikhil Wagle, Sara M Tolaney. A phase I/IIb study of palbociclib (PALBO) plus everolimus (EVE) and exemestane (EXE) in hormone-receptor positive (HR+)/HER2- metastatic breast cancer (MBC) after progression on a CDK4/6 inhibitor (CDK4/6i): Results of the phase II study [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P5-11-04.

Background: In the Phase 3 IMpassion130 (NCT02425891) trial in metastatic triple-negative breast cancer (mTNBC), first-line atezolizumab + nab-paclitaxel (A+nP) significantly improved PFS vs placebo + nab-paclitaxel (P+nP) in the intent-to-treat (ITT) and PD-L1+ (PD-L1-stained immune cells [IC] ≥ 1% of the tumor area by VENTANA PD-L1 SP142 assay) populations. SP142 is currently the only validated assay for selecting patients who may derive benefit with A+nP. In post-hoc analyses of IMpassion130 (Rugo, ESMO 2019, submitted), PD-L1 status was also evaluated by Dako 22C3 and VENTANA SP263 assays. The SP142+ population (IC ≥ 1%; 46% prevalence) was captured within the 22C3 (CPS ≥ 1, 81% prevalence) and SP263 (IC ≥ 1%, 75% prevalence) subgroups, which identified more patients (pts) with PD-L1+ tumors. A+nP clinical activity was highest in pts identified as PD-L1+ by both SP142 and 22C3/SP263. HRs for clinical activity were lower in pts identified as PD-L1+ by 22C3/SP163, but PD-L1- by SP142. There was no suggestion of clinical benefit in pts identified as PD-L1- by both SP142 and 22C3/SP263. In the current retrospective exploratory analysis, we attempted to harmonize the PD-L1 assays by identifying cutoffs for 22C3 or SP263 that replicate the SP142 IC ≥ 1% population. Methods: Samples from IMpassion130 were assessed by a central laboratory for PD-L1 expression using VENTANA SP142 or SP263 IHC assays or Dako 22C3 IHC assay. Optimal cutoffs for 22C3 and SP263 were identified as those that maximize the analytical concordance (defined as overall percentage agreement; OPA) with the clinically validated SP142 IC 1% cutoff as the reference standard. Association with clinical activity was analyzed in the biomarker-evaluable population (BEP) in tumor samples from pts evaluated by the three PD-L1 assays. Results: In the BEP (n = 614; 68% of ITT), the intraclass correlation index (Spearman r) between SP142 IC and 22C3 CPS or SP263 IC was 0.57 and 0.69, respectively. The model-derived cutoffs with highest OPA (75%) for SP142 IC ≥ 1% were CPS 10 for 22C3 and IC 4% for SP263. Compared with our previous analyses at standard cutoffs (22C3 CPS 1; SP263 IC 1%), model-derived cutoffs resulted in negative percentage agreement increases from 45% to 74% (22C3) and from 34% to 77% (SP263), accompanied by positive percentage agreement reductions from 98% to 74% (22C3) and to 73% (SP263). These data suggest that the SP142 assay may identify a different population from the 22C3 or SP263 assays. For 22C3 at CPS 10, 36% of pts were SP142+/22C3+, but 10% were SP142+/22C3-, and 17% SP142-/22C3+. For SP263 at IC 4%, 34% of pts were SP142+/SP263+, but 12% were SP142+/SP263-, and 12% SP142-/SP263+. See table for prevalences, medians and HR point estimates for PFS and OS with the model-derived cutoffs. Conclusions: The suboptimal OPAs achieved with the model-derived cutoffs indicate that the assays could not be harmonized. Differences in SP142+ vs 22C3+ or SP263+ populations at model-derived cutoffs suggest that SP142, 22C3 and SP263 may not identify the same tumor biology. Additional data are required to understand these differences. Findings from these hypothesis-generating, post-hoc exploratory analyses based on mathematical modeling should be interpreted with caution. Currently, the VENTANA PD-L1 SP142 IHC assay (IC ≥ 1%) is the only clinically validated companion assay to select pts with mTNBC for A+nP treatment. Populationn (%)Median PFS, moPFS HRMedian OS, moOS HRA+nPP+nP(95% CI)A+nPP+nP(95% CI)BEP614 (100)7.45.40.7221.119.20.84(0.61, 0.86)(0.68, 1.03)SP142IC ≥ 1%285 (46)8.34.10.627.317.90.74(0.47, 0.78)(0.54, 1.01)IC < 1%329 (54)5.75.60.8620.820.70.95(0.68, 1.09)(0.72, 1.27)22C3CPS ≥ 10325 (53)7.55.50.712218.70.77(0.56, 0.91)(0.57, 1.03)CPS < 10289 (47)5.85.40.7320.219.40.94(0.57, 0.93)(0.69, 1.26)SP263IC ≥ 4%286 (47)8.75.50.6428.919.60.71(0.49, 0.83)(0.51, 0.98) Citation Format: Hope Rugo, Sherene Loi, Sylvia Adams, Peter Schmid, Andreas Schneeweiss, Carlos H Barrios, Hiroji Iwata, Véronique Diéras, Eric P Winer, Mark M Kockx, Dieter Peeters, Stephen Y Chui, Jennifer C Lin, Anh Nguyen Duc, Guiseppe Viale, Luciana Molinero, Leisha A Emens. Exploratory analytical harmonization of PD-L1 immunohistochemistry assays in advanced triple-negative breast cancer: A retrospective substudy of IMpassion130 [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr PD1-07.

Background: CRA is a surrogate for ovarian toxicity and associated risk of infertility and long-term menopausal symptoms. Therefore, it is important to assess and report the rate of CRA when we study a new neoadjuvant treatment regimen. In the Adjuvant Paclitaxel and Tratuzumab (APT) trial, we found that CRA rate associated with adjuvant TH (12 weeks of paclitaxel and a year of trastuzumab) for human epidermal growth factor receptor-2 (HER2)-positive breast cancer was lower than historically seen with cyclophosphamide-based regimens. The ATEMPT trial allowed a direct comparison of the CRA rate associated with TDM1 and TH. Methods: The ATEMPT trial randomized patients (pts) with Stage I HER2+ breast cancer 3:1 to T-DM1 3.6 mg/kg IV every 3 weeks (w) x17 vs. T 80 mg/m2 IV with H qw x 12 (4 mg/kg load →2 mg/kg), followed by H (6 mg/kg q3w x 13). Participants who reported that they were premenopausal at enrollment were asked to complete menstrual surveys at baseline and every 6-12 months throughout a 36 month follow-up period. For this analysis, CRA was defined as report of no menstruation within the prior six months on a survey completed 18 months after enrollment. Results: Of 512 ATEMPT enrollees, 497 began protocol therapy, 130 (26%) were premenopausal at enrollment and answered baseline menstrual questions, 42 of these 130 were excluded from the current analyses because they did not complete the 18-month survey, and 7 of the remaining 88 had received gonadotropin-releasing hormone agonist before 18 months, leaving 81 for analysis. None had undergone hysterectomy or oophorectomy. Median age was 44 (range 23-53) among the TH patients (n=20), and 46 (range 34-54) among the T-DM1 patients (n=61). On the 18-month survey, 45% of women treated with TH reported at least one one episode of menses during the prior 6 months compared to 75% of women in the T-DM1 arm (p=0.011). Among those ≤ 40 years old, 50% of TH patients and 100% of T-DM1 patients reported menstruation at that timepoint. Please see Table for additional data in subgroups. Conclusions: In this relatively small sample, CRA at 18 months was less common after adjuvant T-DM1 than after TH (though even with TH, nearly half of women did menstruate after chemotherapy, even in the subset aged 41+). This will be reassuring to young patients with HER2-positive breast cancer who seek to maintain ovarian function. Larger studies are needed to confirm this finding and to assess a possible differential impact of these drugs on subgroups based on age, endocrine therapy, and body mass index. Additional research should also focus on menopausal symptoms and actual fertility after receipt of T-DM1. Menstruation in 61 T-DM1 arm patients with informative surveys at 18 monthsMenstruation in 20 TH arm patients with informative surveys at 18 monthsAge at study entry95% CI95% CI≤4012/12 (100%)74-100%4/8 (50%)16-84%41+34/49 (69%)55-82%5/12 (42%)15-72%BMI Citation Format: Kathryn J. Ruddy, Lorenzo Trippa, Jiani Hu, William T. Barry, Chau T. Dang, Denise A. Yardley, Steven J. Isakoff, Vincente V. Valero, Meredith G. Faggen, Therese M. Mulvey, Ron Bose, Douglas J. Weckstein, Antonio C. Wolff, Katherine E. Reeder-Hayes, Hope S. Rugo, Bhuvaneswari Ramaswamy, Dan S. Zuckerman, Lowell L. Hart, Vijayakrishna K. Gadi, Michael Constantine, Kit L. Cheng, Frederick M. Briccetti, Bryan P. Schneider, A. Merrill Garrett, P. Kelly Marcom, Kathy S. Albain, Patricia A. DeFusco, Nadine M. Tung, Blair M. Ardman, Rita Nanda, Rachel C. Jankowitz, Michelle K. DeMeo, Harold J. Burstein, Eric P. Winer, Ian E. Krop, Ann H. Partridge, Sara M. Tolaney. Chemotherapy-related amenorrhea (CRA) after adjuvant trastuzumab emtansine (T-DM1) compared to paclitaxel in combination with trastuzumab (TH) (TBCRC033: ATEMPT trial) [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P2-13-02.