A phase II study of atezolizumab, pertuzumab, and high-dose trastuzumab for central nervous system metastases in patients with HER2-positive breast cancer.

PURPOSE: Patients with HER2-positive breast cancer brain metastases have few effective systemic therapy options. In a prior study, pertuzumab with high-dose trastuzumab demonstrated a high clinical benefit rate (CBR) in the central nervous system (CNS) in patients with brain metastases. The current trial evaluated whether the addition of atezolizumab to this regimen would produce further improvements in CNS response. PATIENTS AND METHODS: This was a single-arm, multi-center, phase II trial of atezolizumab, pertuzumab, and high-dose trastuzumab for patients with HER2-positive breast cancer brain metastases. Participants received atezolizumab 1200 mg IV every 3 weeks (q3w), pertuzumab (loading dose 840 mg IV, then 420 mg IV q3w), and high-dose trastuzumab (6 mg/kg IV weekly for 24 weeks, then 6 mg/kg IV q3w). The primary endpoint was CNS overall response rate (ORR) per Response Assessment in Neuro-Oncology Brain Metastases (RANO-BM) criteria. Key secondary endpoints included CBR, overall survival (OS), and safety and tolerability of the combination. RESULTS: Among 19 enrolled participants, two had a confirmed intracranial partial response for a CNS-ORR of 10.5% (90% CI: 1.9%-29.6%). The study did not meet the prespecified efficacy threshold and was terminated early. The CBR was 42.1% at 18 weeks and 31.6% at 24 weeks. Seven patients (36.8%) required a dose delay or hold, and the most frequent any-grade adverse events were diarrhea (26.3%) and fatigue (26.3%). CONCLUSIONS: The addition of atezolizumab to pertuzumab plus high-dose trastuzumab does not result in improved CNS responses in patients with HER2-positive breast cancer brain metastases.

PRECISE: Preoperative Radiation Therapy to Elicit Critical Immune Stimulating Effects - A Phase 2 Clinical Trial.

PURPOSE: Radiation therapy is an underinvestigated tool for priming the immune system in intact human breast cancers. We sought here to investigate if a preoperative radiation therapy boost delivered was associated with a significant change in tumor-infiltrating lymphocytes (TILs) in the tumor in estrogen receptor positive, HER2Neu nonamplified breast cancers. METHODS AND MATERIALS: A total of 20 patients were enrolled in a phase 2 clinical trial and received either 7.5 Gy × 1 fraction or 2 Gy × 5 fractions, completed 6 to 8 days before surgery. Percent stromal TILs were evaluated on hematoxylin and eosin-stained samples. Short-term safety was assessed based on time to surgery, toxicities, and cosmesis up to 6 months after boost. RESULTS: Stromal TIL increased 6 to 8 days after completion of boost radiation therapy (median 3.0 [IQR, 1.0-6.5]) before radiation therapy versus median 5.0 (IQR, 1.5-8.0) after radiation therapy, P = .0037. Zero grade ≥3 toxicities up to 6 months after boost were experienced. In all, 94% (16/17) patients with 6-month follow-up cosmetic assessment after breast conservation had good-excellent cosmesis by physician assessment. CONCLUSION: In this phase 2 trial, preoperative radiation therapy boost resulted in a short-term increase in stromal TIL with minimal toxicities. Preoperative breast radiation therapy appears to be safe and may be a feasible means for priming the tumor microenvironment.

Generative artificial intelligence as a source of breast cancer information for patients: Proceed with caution.

BACKGROUND: This study evaluated the accuracy, clinical concordance, and readability of the chatbot interface generative pretrained transformer (ChatGPT) 3.5 as a source of breast cancer information for patients. METHODS: Twenty questions that patients are likely to ask ChatGPT were identified by breast cancer advocates. These were posed to ChatGPT 3.5 in July 2023 and were repeated three times. Responses were graded in two domains: accuracy (4-point Likert scale, 4 = worst) and clinical concordance (information is clinically similar to physician response; 5-point Likert scale, 5 = not similar at all). The concordance of responses with repetition was estimated using intraclass correlation coefficient (ICC) of word counts. Response readability was calculated using the Flesch Kincaid readability scale. References were requested and verified. RESULTS: The overall average accuracy was 1.88 (range 1.0-3.0; 95% confidence interval [CI], 1.42-1.94), and clinical concordance was 2.79 (range 1.0-5.0; 95% CI, 1.94-3.64). The average word count was 310 words per response (range, 146-441 words per response) with high concordance (ICC, 0.75; 95% CI, 0.59-0.91; p < .001). The average readability was poor at 37.9 (range, 18.0-60.5) with high concordance (ICC, 0.73; 95% CI, 0.57-0.90; p < .001). There was a weak correlation between ease of readability and better clinical concordance (-0.15; p = .025). Accuracy did not correlate with readability (0.05; p = .079). The average number of references was 1.97 (range, 1-4; total, 119). ChatGPT cited peer-reviewed articles only once and often referenced nonexistent websites (41%). CONCLUSIONS: Because ChatGPT 3.5 responses were incorrect 24% of the time and did not provide real references 41% of the time, patients should be cautioned about using ChatGPT for medical information.

Integrative multi-omic profiling of triple-negative breast cancer for identifying suitable therapies.

PURPOSE: Triple-negative breast cancer (TNBC) is a heterogenous disease that carries the poorest prognosis of all breast cancers. Although novel TNBC therapies in development are frequently targeted towards tumors carrying a specific genomic, transcriptomic, or protein biomarker, how these biomarkers are correlated is poorly understood. EXPERIMENTAL DESIGN: To better understand the molecular features of TNBC and their correlation with one another, we performed multi-modal profiling on a cohort of 95 TNBCs. Our approach involved quantifying tumor-infiltrating lymphocytes through H&E staining, assessing the abundance of retinoblastoma (Rb), androgen receptor (AR), and PD-L1 proteins through immunohistochemistry, and carrying out transcriptomic profiling using the Nanostring BC360 platform, targeted DNA sequencing on a subset of cases, as well as evaluating associations with overall survival. RESULTS: Levels of RB1 mRNA and RB protein are better correlated with markers of Rb functionality than is RB1 mutational status. Luminal AR tumors clustered into two groups with transcriptomes that cluster with either basal or mesenchymal tumors. Tumors classified as PD-L1-positive by presence of immune or tumor cells showed similar biological characteristics. HER2-low TNBC showed no distinct biological phenotype when compared to HER2-zero. The majority of TNBCs classified as basal or HER2-enriched by PAM50, the latter showing significantly improved overall survival. CONCLUSIONS: Our study contributes new insights into biomarker utility for identifying suitable TNBC therapies and the intercorrelations between genomic, transcriptomic, protein, and cellular biomarkers. Additionally, our rich data resource can be used by other researchers to explore the interplay between DNA, RNA, and protein biomarkers in TNBC.

Potential Overtreatment of DCIS in Patients with Limited Life Expectancy.

INTRODUCTION: As the benefits of intensive locoregional therapy for ductal carcinoma in situ (DCIS) are realized over time in older adults, life expectancy may help to guide treatment decisions. We examined whether life expectancy was associated with extent of locoregional therapy in this population. PATIENTS AND METHODS: Women ≥ 70 years old with < 5 cm of DCIS diagnosed 2010-2015 were identified in the Surveillance, Epidemiology, and End Results (SEER)-Medicare dataset and categorized by a life expectancy ≤ 5 or > 5 years, defined by a validated claims-based measure. Differences in locoregional therapy (mastectomy + axillary surgery, mastectomy-only, lumpectomy + radiation therapy (RT) + axillary surgery, lumpectomy + RT, lumpectomy-only, and no treatment) by life expectancy were assessed using Pearson chi-squared tests. Generalized linear mixed models were used to identify factors associated with receipt of lumpectomy-only. RESULTS: Of 5346 women (median age of 75 years, range 70-97 years), 927 (17.3%) had a life expectancy ≤ 5 years. Of the 4041 patients who underwent lumpectomy, 710 (13.3%) underwent axillary surgery. More patients with life expectancy ≤ 5 years underwent lumpectomy-only (39.4% versus 27%), mastectomy-only (8.1% versus 5.3%), or no treatment (5.8% versus 3.2%; p < 0.001). On multivariable analysis, women with life expectancy ≤ 5 years had a significantly greater likelihood of undergoing lumpectomy-only [OR 1.90, 95% CI (1.63-2.22)]. CONCLUSIONS: Life expectancy is associated with lower-intensity locoregional therapy for older women with DCIS, yet a large proportion of patients with a life expectancy ≤ 5 years received RT and axillary surgery, highlighting potential overtreatment and opportunities to de-escalate locoregional therapy in older adults.

Patient-Reported Outcomes 10 Years After Breast-Conserving Surgery for Early-Stage Breast Cancer.

BACKGROUND: Patient-reported outcomes (PROs) are a critical component of value-based care. Limited data exist describing long-term PROs in patients undergoing breast-conserving surgery (BCS). PATIENTS AND METHODS: Patients undergoing surgery for stage 0-III breast cancer at our institution from 2002 to 2012 who agreed to be contacted were invited to participate in a cross-sectional PRO study. Health-related quality of life outcomes using BREAST-Q, EORTC QLQ-C30, and EORTC QLQ-BR45 were collected. Patients reporting chemotherapy within 6 months of receiving the survey were excluded. For this work, we focused on patients who underwent BCS. Multivariable linear regression was performed to identify factors associated with PRO scores, adjusting for age, time since surgery, anatomic stage, molecular subtype, receipt of systemic and/or radiation therapy (RT), locoregional recurrence, or contralateral breast cancer. RESULTS: Among 562 interested and eligible patients, 437 (78%) responded; median time from surgery to survey completion was 10.4 years (interquartile range: 8.0-13.5). Median age at surgery was 53 years (standard deviation 9.8 years), ≥ 90% were white, had upfront surgery for early-stage disease, and completed adjuvant RT. Physical and psychological well-being scores were generally high, with more variation seen for sexual well-being and satisfaction with breasts. CONCLUSION: This study provides long-term PRO data for patients treated with BCS, demonstrating the ongoing association of breast cancer surgery with quality of life in the survivorship period and highlighting the importance of examining PROs beyond the perioperative period. These data also provide important reference values for the interpretation of PROs among women treated with BCS as we move towards value-based care.

Adjuvant Trastuzumab Emtansine Versus Paclitaxel Plus Trastuzumab for Stage I Human Epidermal Growth Factor Receptor 2-Positive Breast Cancer: 5-Year Results and Correlative Analyses From ATEMPT.

PURPOSE: Long-term outcomes of patients with stage I human epidermal growth factor receptor 2 (HER2)-positive breast cancer receiving adjuvant trastuzumab emtansine (T-DM1) remain undefined, and prognostic predictors represent an unmet need. METHODS: In the ATEMPT phase II trial, patients with stage I centrally confirmed HER2-positive breast cancer were randomly assigned 3:1 to adjuvant T-DM1 for 1 year or paclitaxel plus trastuzumab (TH). Coprimary objectives were to compare the incidence of clinically relevant toxicities between arms and to evaluate invasive disease-free survival (iDFS) with T-DM1. Correlative analyses included the HER2DX genomic tool, multiomic evaluations of HER2 heterogeneity, and predictors of thrombocytopenia. RESULTS: After a median follow-up of 5.8 years, 11 iDFS events were observed in the T-DM1 arm, consistent with a 5-year iDFS of 97.0% (95% CI, 95.2 to 98.7). At 5 years, the recurrence-free interval (RFI) was 98.3% (95% CI, 97.0 to 99.7), the overall survival was 97.8% (95% CI, 96.3 to 99.3), and the breast cancer-specific survival was 99.4% (95% CI, 98.6 to 100). Comparable iDFS was observed with T-DM1 irrespective of tumor size, hormone receptor status, centrally determined HER2 immunohistochemical score, and receipt of T-DM1 for more or less than 6 months. Although ATEMPT was not powered for this end point, the 5-year iDFS in the TH arm was 91.1%. Among patients with sufficient tissue for HER2DX testing (n = 187), 5-year outcomes significantly differed according to HER2DX risk score, with better RFI (98.1% v 81.8%, hazard ratio [HR], 0.10, P = .01) and iDFS (96.3% v 81.8%, HR, 0.20, P = .047) among patients with HER2DX low-risk versus high-risk tumors, respectively. CONCLUSION: Adjuvant T-DM1 for 1 year leads to outstanding long-term outcomes for patients with stage I HER2-positive breast cancer. A high HER2DX risk score predicted a higher risk of recurrence in ATEMPT.

Arm morbidity and financial difficulty in breast cancer survivors.

PURPOSE: Long-term upper extremity symptoms after breast cancer treatment may impact patient-reported financial difficulty. In this cross-sectional investigation, we hypothesized that severity of arm symptoms would be associated with greater financial difficulty. METHODS: Stage 0-III breast cancer patients treated at our institution from 2002 to 2012 were recruited for a 2018 survey study appraising disease-specific patient-centered outcomes using EORTC-QLQ-BR23 and EORTC-QLQ-C30 questionnaires. The association between Arm Symptom (AS) score and Financial Impact (FI) score was assessed, adjusting for clinically relevant variables. RESULTS: Of 1126 interested participants, 882 (78%) responded to surveys. Three hundred fourteen (36%) with incomplete responses were excluded. Median time from surgery was 9 years; 181 (32%) and 117 (21%) had mastectomy with or without reconstruction, 126 (22%) received postmastectomy radiation (PMRT), and 221 (39%) underwent axillary lymph node dissection. 76 (13%) reported some degree of financial difficulty; 10 (2%) the highest degree of difficulty. Of 217 (38%) patients experiencing arm symptoms, 60 (28%) had severe symptoms. Seven (70%) of those with highest degree of financial difficulty had severe arm symptoms. Younger age at surgery (p = .029), mastectomy with reconstruction (p = 0.003), Hispanic ethnicity (p < 0.001), PMRT (p = 0.027), recurrence (p < 0.001), and higher AS score (p < 0.001) were associated with greater financial difficulty. On multivariable analysis, AS score, younger age, Hispanic ethnicity, and recurrence remained associated with financial difficulty. CONCLUSION: In this study, younger age, Hispanic ethnicity, and arm morbidity were associated with increased risk for financial difficulty. Clarifying how treatment-related adverse events such as arm morbidity increase financial hardship may guide interventions to mitigate this burden.

Factors Influencing Implementation of the Commission on Cancer's Breast Synoptic Operative Report (Alliance A20_Pilot9).

BACKGROUND: The technical aspects of cancer surgery have a significant impact on patient outcomes. To monitor surgical quality, in 2020, the Commission on Cancer (CoC) revised its accreditation standards for cancer surgery and introduced the synoptic operative reports (SORs). The standardization of SORs holds promise, but successful implementation requires strategies to address key implementation barriers. This study aimed to identify the barriers and facilitators to implementing breast SOR within diverse CoC-accredited programs. METHODS: In-depth semi-structured interviews were conducted with 31 health care professionals across diverse CoC-accredited sites. The study used two comprehensive implementation frameworks to guide data collection and analysis. RESULTS: Successful SOR implementation was impeded by disrupted workflows, surgeon resistance to change, low prioritization of resources, and poor flow of information despite CoC's positive reputation. Participants often lacked understanding of the requirements and timeline for breast SOR and were heavily influenced by prior experiences with templates and SOR champion relationships. The perceived lack of monetary benefits (to obtaining CoC accreditation) together with the significant information technology (IT) resource requirements tempered some of the enthusiasm. Additionally, resource constraints and the redirection of personnel during the COVID-19 pandemic were noted as hurdles. CONCLUSIONS: Surgeon behavior and workflow change, IT and personnel resources, and communication and networking strategies influenced SOR implementation. During early implementation and the implementation planning phase, the primary focus was on achieving buy-in and initiating successful roll-out rather than effective use or sustainment. These findings have implications for enhancing standardization of surgical cancer care and guidance of future strategies to optimize implementation of CoC accreditation standards.

Checkpoint inhibition for early-stage hormone receptor-positive breast cancer.

INTRODUCTION: Most patients with breast cancer have early-stage hormone receptor (HR)-positive, human epidermal growth factor receptor-2 (HER2)-negative disease. Even though the prognosis for most of these patients is good, there is a need to identify patients at risk for poor outcomes and to develop strategies to mitigate this risk. AREAS COVERED: The addition of immunotherapy to standard neoadjuvant chemotherapy represents a promising option for select patients with HR-positive early breast cancer. Three randomized clinical trials have shown favorable results to date. In this review, we discuss the findings of I-SPY2, CheckMate 7FL (NCT04109066), and KEYNOTE-756 (NCT03725059). EXPERT OPINION: Despite the promising results of these trials, there are unanswered questions that need to be considered before incorporating neo/adjuvant immunotherapy in the treatment paradigm of early-stage HR-positive breast cancer. One example of an unanswered question is patient selection. Because the regimens used in these protocols are associated with long-term toxicities, identifying the patients who are more likely to derive a benefit from these agents, such as through the use of biomarkers, is critical. A second example is the optimal integration of adjuvant therapies that improve invasive disease-free survival, such as abemaciclib and ribociclib, which are not safely administered concurrently with immunotherapy.

The Clinical Utility of a 7-Gene Biosignature on Radiation Therapy Decision Making in Patients with Ductal Carcinoma In Situ Following Breast-Conserving Surgery: An Updated Analysis of the DCISionRT® PREDICT Study.

BACKGROUND: Breast-conserving surgery (BCS) followed by adjuvant radiotherapy (RT) is a standard treatment for ductal carcinoma in situ (DCIS). A low-risk patient subset that does not benefit from RT has not yet been clearly identified. The DCISionRT test provides a clinically validated decision score (DS), which is prognostic of 10-year in-breast recurrence rates (invasive and non-invasive) and is also predictive of RT benefit. This analysis presents final outcomes from the PREDICT prospective registry trial aiming to determine how often the DCISionRT test changes radiation treatment recommendations. METHODS: Overall, 2496 patients were enrolled from February 2018 to January 2022 at 63 academic and community practice sites and received DCISionRT as part of their care plan. Treating physicians reported their treatment recommendations pre- and post-test as well as the patient's preference. The primary endpoint was to identify the percentage of patients where testing led to a change in RT recommendation. The impact of the test on RT treatment recommendation was physician specialty, treatment settings, individual clinical/pathological features and RTOG 9804 like criteria. Multivariate logisitc regression analysis was used to estimate the odds ratio (ORs) for factors associated with the post-test RT recommendations. RESULTS: RT recommendation changed 38% of women, resulting in a 20% decrease in the overall recommendation of RT (p < 0.001). Of those women initially recommended no RT (n = 583), 31% were recommended RT post-test. The recommendation for RT post-test increased with increasing DS, from 29% to 66% to 91% for DS <2, DS 2-4, and DS >4, respectively. On multivariable analysis, DS had the strongest influence on final RT recommendation (odds ratio 22.2, 95% confidence interval 16.3-30.7), which was eightfold greater than clinicopathologic features. Furthermore, there was an overall change in the recommendation to receive RT in 42% of those patients meeting RTOG 9804-like low-risk criteria. CONCLUSIONS: The test results provided information that changes treatment recommendations both for and against RT use in large population of women with DCIS treated in a variety of clinical settings. Overall, clinicians changed their recommendations to include or omit RT for 38% of women based on the test results. Based on published clinical validations and the results from current study, DCISionRT may aid in preventing the over- and undertreatment of clinicopathological 'low-risk' and 'high-risk' DCIS patients. TRIAL REGISTRATION: ClinicalTrials.gov identifier: NCT03448926 ( https://clinicaltrials.gov/study/NCT03448926 ).

Physician-level variation in axillary surgery in older adults with T1N0 hormone receptor-positive breast cancer: A retrospective population-based cohort study.

INTRODUCTION: We sought to determine how considerations specific to older adults impact between- and within-surgeon variation in axillary surgery use in women ≥70 years with T1N0 HR+ breast cancer. MATERIALS AND METHODS: Females ≥70 years with T1N0 HR+/HER2-negative breast cancer diagnosed from 2013 to 2015 in SEER-Medicare were identified and linked to the American Medical Association Masterfile. The outcome of interest was axillary surgery. Key patient-level variables included the Charlson Comorbidity Index (CCI) score, frailty (based on a claims-based frailty index score), and age (≥75 vs <75). Multilevel mixed models with surgeon clusters were used to estimate the intracluster correlation coefficient (ICC) (between-surgeon variance), with 1-ICC representing within-surgeon variance. RESULTS: Of the 4410 participants included, 6.1% had a CCI score of ≥3, 20.7% were frail, and 58.3% were ≥ 75 years; 86.1% underwent axillary surgery. No surgeon omitted axillary surgery in all patients, but 42.3% of surgeons performed axillary surgery in all patients. In the null model, 10.5% of the variance in the axillary evaluation was attributable to between-surgeon differences. After adjusting for CCI score, frailty, and age in mixed models, between-surgeon variance increased to 13.0%. DISCUSSION: In this population, axillary surgery varies more within surgeons than between surgeons, suggesting that surgeons are not taking an "all-or-nothing" approach. Comorbidities, frailty, and age accounted for a small proportion of the variation, suggesting nuanced decision-making may include additional, unmeasured factors such as differences in surgeon-patient communication.

Breast Articles From 2023: Informing Practice Across the Continuum of Care.

With new investigations and clinical trials in breast oncology reported every year, it is critical that surgeons be aware of advances and insights into the evolving care paradigms and treatments available to their patients. This article highlights five publications found to be particularly impactful this past year. These articles report on efforts to select the minimal effective dose of tamoxifen for prevention, to challenge the existing age-based screening guidelines as they relate to race and ethnicity, to refine axillary management treatment standards, to optimize systemic therapy in multidisciplinary care settings, and to reduce the burden of breast cancer-related lymphedema after treatment. Taken together, these efforts have an impact on all facets of the continuum of care from prevention and screening through treatment and survivorship.

Clinicopathological characteristics and eligibility for adjuvant olaparib of germline BRCA1/2 mutation carriers with HER2-negative early breast cancer.

Following the survival benefit demonstrated in the OlympiA trial, one year of adjuvant olaparib is now recommended for all patients with germline BRCA1/2 pathogenic/likely pathogenic variants (PV) and high-risk, HER2-negative early breast cancer after chemotherapy. However, optimal identification of high-risk patients who may derive benefit from this genomically-directed therapy is debated. In this study, we sought to characterize the real-world proportion of gBRCA1/2 PV carriers eligible for adjuvant olaparib according to the OlympiA criteria, and to compare clinicopathologic characteristics and outcomes between eligible and ineligible patients.

Racial disparities in outcomes of patients with stage I-III triple-negative breast cancer after adjuvant chemotherapy: a post-hoc analysis of the E5103 randomized trial.

PURPOSE: Breast cancer mortality is higher in Black women than other racial groups. This difference has been partially attributed to a higher proportion of triple-negative breast cancer (TNBC). However, it is uncertain if survival disparities exist in racially diverse TNBC patients receiving similar treatments. Here, we examine racial differences in disease-related outcomes in TNBC patients treated on the E5103 clinical trial. METHODS: From 2007 to 2011, 4,994 patients with stage I-III HER2-negative breast cancer were randomized to adjuvant chemotherapy with or without bevacizumab. This analysis was limited to the subset of 1,742 TNBC patients with known self-reported race. Unadjusted Kaplan-Meier curves and adjusted Cox-Proportional Hazards models were used to determine breast cancer events and survival outcomes. RESULTS: Of the analysis population, 51 (2.9%) were Asian, 269 (15.4%) Black, and 1422 (81.6%) White. Median age was 51 years. Patient characteristics, treatment arm, and local therapies were similar across racial groups. White women were more commonly node-negative (56% vs. 49% and 44% in Asian and Black women, respectively; p < 0.01). At a median follow-up of 46 months, unadjusted Kaplan-Meier locoregional and distant recurrence, and disease-free and overall survival, did not differ significantly by race. In Cox models adjusted for patient and tumor characteristics and treatment arm, race was not associated with any disease event. Larger tumor size and nodal involvement were consistently associated with breast cancer events. CONCLUSION: This clinical trial population of similarly treated TNBC patients showed no racial differences in breast cancer outcomes. Disease extent, rather than race, was associated with disease events.

Durvalumab and tremelimumab before surgery in patients with hormone receptor positive, HER2-negative stage II-III breast cancer.

A clinical trial was conducted to assess the feasibility of enrolling patients with Stage II or III hormone receptor positive (HR+)/HER2-negative breast cancer to pre-operative dual PD-L1/CTLA-4 checkpoint inhibition administered prior to neoadjuvant chemotherapy (NACT). Eight eligible patients were treated with upfront durvalumab and tremelimumab for two cycles. Patients then received NACT prior to breast surgery. Seven patients had baseline and interval breast ultrasounds after combination immunotherapy and the responses were mixed: 3/7 patients experienced a ≥30% decrease in tumor volume, 3/7 a ≥30% increase, and 1 patient had stable disease. At the time of breast surgery, 1/8 patients had a pathologic complete response (pCR). The trial was stopped early after 3 of 8 patients experienced immunotherapy-related toxicity or suspected disease progression that prompted discontinuation or a delay in the administration of NACT. Two patients experienced grade 3 immune-related adverse events (1 with colitis, 1 with endocrinopathy). Analysis of the tumor microenvironment after combination immunotherapy did not show a significant change in immune cell subsets from baseline. There was limited benefit for dual checkpoint blockade administered prior to NACT in our study of 8 patients with HR+/HER2-negative breast cancer.