Comprehensive genomic profiling of ESR1, PIK3CA, AKT1, and PTEN in HR(+)HER2(-) metastatic breast cancer: prevalence along treatment course and predictive value for endocrine therapy resistance in real-world practice.

BACKGROUND: The treatment landscape for HR(+)HER2(-) metastatic breast cancer (MBC) is evolving for patients with ESR1 mutations (mut) and PI3K/AKT pathway genomic alterations (GA). We sought to inform clinical utility for comprehensive genomic profiling (CGP) using tissue (TBx) and liquid biopsies (LBx) in HR(+)HER2(-) MBC. METHODS: Records from a de-identified breast cancer clinicogenomic database for patients who underwent TBx/LBx testing at Foundation Medicine during routine clinical care at ~ 280 US cancer clinics between 01/2011 and 09/2023 were assessed. GA prevalence [ESR1mut, PIK3CAmut, AKT1mut, PTENmut, and PTEN homozygous copy loss (PTENloss)] were calculated in TBx and LBx [stratified by ctDNA tumor fraction (TF)] during the first three lines of therapy. Real-world progression-free survival (rwPFS) and overall survival (rwOS) were compared between groups by Cox models adjusted for prognostic factors. RESULTS: ~ 60% of cases harbored 1 + GA in 1st-line TBx (1266/2154) or LBx TF ≥ 1% (80/126) and 26.5% (43/162) in LBx TF < 1%. ESR1mut was found in 8.1% TBx, 17.5% LBx TF ≥ 1%, and 4.9% LBx TF < 1% in 1st line, increasing to 59% in 3rd line (LBx TF ≥ 1%). PTENloss was detected at higher rates in TBx (4.3%) than LBx (1% in TF ≥ 1%). Patients receiving 1st-line aromatase inhibitor + CDK4/6 inhibitor (n = 573) with ESR1mut had less favorable rwPFS and rwOS versus ESR1 wild-type; no differences were observed for fulvestrant + CDK4/6 inhibitor (n = 348). CONCLUSION: Our study suggests obtaining TBx for CGP at time of de novo/recurrent diagnosis, followed by LBx for detecting acquired GA in 2nd + lines. Reflex TBx should be considered when ctDNA TF < 1%.

Neoadjuvant pembrolizumab+chemotherapy/adjuvant pembrolizumab for Early-Stage Triple-Negative breast cancer: Quality-of-Life results from randomized KEYNOTE-522 study.

BACKGROUND: In KEYNOTE-522 (NCT03036488), neoadjuvant pembrolizumab+chemotherapy then adjuvant pembrolizumab significantly improved pathological complete response and event-free survival vs neoadjuvant chemotherapy in early-stage triple-negative breast cancer (TNBC). We report patient-reported outcomes (PROs) from KEYNOTE-522. METHODS: Patients were randomized 2:1 to neoadjuvant pembrolizumab 200 mg or placebo every 3 weeks, plus 4 cycles of paclitaxel+carboplatin then 4 cycles of doxorubicin (or epirubicin)+cyclophosphamide. After surgery, patients received adjuvant pembrolizumab or placebo for up to 9 cycles. EORTC QLQ-30 and QLQ-BR23 were prespecified secondary objectives. Between-group differences in least squares (LS) mean change from baseline (day 1/cycle 1 in both neoadjuvant and adjuvant phases) to the prespecified latest time point with ≥60%/80% completion/compliance were assessed using a longitudinal model (no alpha error assigned). RESULTS: Week 21 (neoadjuvant phase) and week 24 (adjuvant phase) were the latest time points at which completion/compliance rates were ≥60%/80%. In the neoadjuvant phase, between-group differences (pembrolizumab+chemotherapy [N = 762] vs placebo+chemotherapy [N = 383]) in LS mean change from baseline to week 21 in QLQ-C30 GHS/QoL, emotional functioning, and physical functioning were -1.04 (95% CI, -3.46 to 1.38), -0.69 (95% CI, -3.13 to 1.75), and -2.85 (95% CI, -5.11 to - 0.60), respectively. In the adjuvant phase, between-group differences (pembrolizumab [N = 539] vs placebo [N = 308]) in LS mean change from baseline to week 24 were -0.41 (95% CI, -2.60 to 1.77), -0.60 (95% CI, -2.99 to 1.79), and -1.57 (95% CI, -3.36 to 0.21). CONCLUSIONS: No substantial differences in PRO assessments were observed between neoadjuvant pembrolizumab+chemotherapy followed by adjuvant pembrolizumab vs neoadjuvant placebo+chemotherapy in early-stage TNBC. TRIAL REGISTRATION: ClinicalTrials.gov, NCT03036488.

Digital droplet PCR analysis of organoids generated from mouse mammary tumors demonstrates proof-of-concept capture of tumor heterogeneity.

Breast cancer metastases exhibit many different genetic alterations, including copy number amplifications (CNA). CNA are genetic alterations that are increasingly becoming relevant to breast oncology clinical practice. Here we identify CNA in metastatic breast tumor samples using publicly available datasets and characterize their expression and function using a metastatic mouse model of breast cancer. Our findings demonstrate that our organoid generation can be implemented to study clinically relevant features that reflect the genetic heterogeneity of individual tumors.

A comprehensive single-cell breast tumor atlas defines epithelial and immune heterogeneity and interactions predicting anti-PD-1 therapy response.

We present an integrated single-cell RNA sequencing atlas of the primary breast tumor microenvironment (TME) containing 236,363 cells from 119 biopsy samples across eight datasets. In this study, we leverage this resource for multiple analyses of immune and cancer epithelial cell heterogeneity. We define natural killer (NK) cell heterogeneity through six subsets in the breast TME. Because NK cell heterogeneity correlates with epithelial cell heterogeneity, we characterize epithelial cells at the level of single-gene expression, molecular subtype, and 10 categories reflecting intratumoral transcriptional heterogeneity. We develop InteractPrint, which considers how cancer epithelial cell heterogeneity influences cancer-immune interactions. We use T cell InteractPrint to predict response to immune checkpoint inhibition (ICI) in two breast cancer clinical trials testing neoadjuvant anti-PD-1 therapy. T cell InteractPrint was predictive of response in both trials versus PD-L1 (AUC = 0.82, 0.83 vs. 0.50, 0.72). This resource enables additional high-resolution investigations of the breast TME.

Impact of neoadjuvant pembrolizumab adherence on pathologic complete response in triple-negative breast cancer: a real-world analysis.

BACKGROUND: The addition of pembrolizumab (pembro) to neoadjuvant chemotherapy (NAC) is standard of care for the treatment of early triple-negative breast cancer (TNBC) after KEYNOTE-522 trial demonstrated improved pathologic complete response (pCR) rates with the combination. However, the optimal treatment strategy for TNBC remains uncertain as questions persist about which patients benefit from pembro and the best treatment schedule and regimen. We identified real-world clinical characteristics and treatment variables associated with response to NAC plus pembro. METHODS: Patients with early TNBC treated with NAC plus pembro between February 2020 and September 2023 were identified. Univariate and multivariate analysis was performed using logistic regression to identify factors associated with pCR. Cox proportional hazard prediction models were used to identify predictors of invasive disease-free survival and overall survival in this cohort. RESULTS: A pCR was achieved in 75 (63.6%) of 118 patients. Age at diagnosis (P = .04), Ki-67 (P = .004), duration from start of pembro to surgery (P = .006) and NAC to surgery (P = .01), number of cycles of pembro (P = .04) and NAC (P = .02), and completion of at least 8 cycles of pembro (P = .015) and NAC (P = .015) were each significantly associated with pCR in univariate analysis. In multivariate analysis, patients younger than 55 years at time of diagnosis (vs age > 55 years) and those completing at least 8 cycles of pembro remained predictive of pCR (OR's 2.50, 2.49, P = .035 and .037, respectively). CONCLUSIONS: In this real-world analysis of patients with TNBC treated with NAC plus pembro, younger age and the completion of at least 8 cycles of pembrolizumab were associated with pCR.

Preoperative immune checkpoint inhibition and cryoablation in early-stage breast cancer.

Local cryoablation can engender systemic immune activation/anticancer responses in tumors otherwise resistant to immune checkpoint blockade (ICB). We evaluated the safety/tolerability of preoperative cryoablation plus ipilimumab and nivolumab in 5 early-stage/resectable breast cancers. The primary endpoint was met when all 5 patients underwent standard-of-care primary breast surgery undelayedly. Three patients developed transient hyperthyroidism; one developed grade 4 liver toxicity (resolved with supportive management). We compared this strategy with cryoablation and/or ipilimumab. Dual ICB plus cryoablation induced higher expression of T cell activation markers and serum Th1 cytokines and reduced immunosuppressive serum CD4+PD-1hi T cells, improving effector-to-suppressor T cell ratio. After dual ICB and before cryoablation, T cell receptor sequencing of 4 patients showed increased T cell clonality. In this small subset of patients, we provide preliminary evidence that preoperative cryoablation plus ipilimumab and nivolumab is feasible, inducing systemic adaptive immune activation potentially more robust than cryoablation with/without ipilimumab.

Single-cell and spatial profiling identify three response trajectories to pembrolizumab and radiation therapy in triple negative breast cancer.

Strategies are needed to better identify patients that will benefit from immunotherapy alone or who may require additional therapies like chemotherapy or radiotherapy to overcome resistance. Here we employ single-cell transcriptomics and spatial proteomics to profile triple negative breast cancer biopsies taken at baseline, after one cycle of pembrolizumab, and after a second cycle of pembrolizumab given with radiotherapy. Non-responders lack immune infiltrate before and after therapy and exhibit minimal therapy-induced immune changes. Responding tumors form two groups that are distinguishable by a classifier prior to therapy, with one showing high major histocompatibility complex expression, evidence of tertiary lymphoid structures, and displaying anti-tumor immunity before treatment. The other responder group resembles non-responders at baseline and mounts a maximal immune response, characterized by cytotoxic T cell and antigen presenting myeloid cell interactions, only after combination therapy, which is mirrored in a murine model of triple negative breast cancer.

Pembrolizumab Plus Chemotherapy Followed by Pembrolizumab in Patients With Early Triple-Negative Breast Cancer: A Secondary Analysis of a Randomized Clinical Trial.

Importance: In the phase 3 KEYNOTE-522 study, addition of pembrolizumab to neoadjuvant chemotherapy followed by adjuvant pembrolizumab significantly increased pathologic complete response (pCR) and event-free survival (EFS) vs neoadjuvant chemotherapy in patients with early triple-negative breast cancer. Objective: To evaluate efficacy and safety outcomes for patients enrolled in East/Southeast Asia (Asia) in KEYNOTE-522. Design, Setting, and Participants: KEYNOTE-522, a multicenter, double-blind, randomized clinical trial, enrolled 1174 patients between March 7, 2017, and September 13, 2018. For interim EFS and overall survival (OS) analyses (data cutoff, March 23, 2021), median follow-up was 39.8 months (range, 30.4-46.9 months) for pembrolizumab plus chemotherapy and 40.8 months (range, 30.1-46.9 months) for placebo plus chemotherapy. Data cutoff for pCR analysis was September 24, 2018. This secondary analysis included adults enrolled in Asia with newly diagnosed, previously untreated, nonmetastatic triple-negative breast cancer (tumor stage T1c and nodal stage N1-2 or tumor stage T2-4 and nodal stage N0-2) and Eastern Cooperative Oncology Group performance status of 0 to 1, regardless of programmed cell death ligand 1 (PD-L1) status. Intervention: Patients were randomized 2:1 to 4 cycles of pembrolizumab (200 mg every 3 weeks) or placebo plus carboplatin and paclitaxel and another 4 cycles of pembrolizumab or placebo plus doxorubicin or epirubicin and cyclophosphamide before surgery. After definitive surgery, patients received pembrolizumab or placebo every 3 weeks for 9 cycles or until recurrence or unacceptable toxic effects. Main Outcomes and Measures: The main outcome was pCR (no evidence of primary tumor after neoadjuvant therapy or carcinoma in situ after neoadjuvant therapy and no regional lymph node involvement after neoadjuvant therapy) at the time of definitive surgery and EFS. Results: A total of 216 of 1174 randomized patients (all female; median [range] age, 46.0 [24.0-71.0] years) were from Korea, Japan, Taiwan, and Singapore (136 in the pembrolizumab plus chemotherapy group and 80 in the placebo plus chemotherapy group). Of these patients, 104 (76.5%) in the pembrolizumab plus chemotherapy group and 60 (75.0%) in the placebo plus chemotherapy group had a tumor PD-L1 combined positive score of 1 or greater. Pathologic complete response was 58.7% (95% CI, 46.7%-69.9%) with pembrolizumab plus chemotherapy and 40.0% (95% CI, 26.4%-54.8%) with placebo plus chemotherapy; benefit was observed regardless of PD-L1 status. Thirteen patients (9.6%) in the pembrolizumab plus chemotherapy group and 20 patients (25.0%) in the placebo plus chemotherapy group had EFS events (hazard ratio, 0.35; 95% CI, 0.17-0.71). The 36-month EFS rate was 91.2% (95% CI, 85.0%-94.9%) with pembrolizumab plus chemotherapy and 77.2% (95% CI, 66.3%-85.0%) with placebo plus chemotherapy. Grade 3 to 4 treatment-related adverse events occurred in 109 patients (80.1%) receiving pembrolizumab plus chemotherapy and 64 patients (81.0%) receiving placebo plus chemotherapy. Conclusions and Relevance: In this subgroup analysis of patients enrolled in Asia in KEYNOTE-522, neoadjuvant pembrolizumab plus chemotherapy followed by adjuvant pembrolizumab led to clinically meaningful improvements in pCR and EFS vs neoadjuvant chemotherapy alone. These findings support the use of neoadjuvant pembrolizumab plus chemotherapy followed by adjuvant pembrolizumab as a standard-of-care therapy for patients in Asian countries with early triple-negative breast cancer. Trial Registration: ClinicalTrials.gov Identifier: NCT03036488.

Antibody-drug conjugates in breast cancer: overcoming resistance and boosting immune response.

Antibody-drug conjugates (ADCs) have emerged as a revolutionary therapeutic class, combining the precise targeting ability of monoclonal antibodies with the potent cytotoxic effects of chemotherapeutics. Notably, ADCs have rapidly advanced in the field of breast cancer treatment. This innovative approach holds promise for strengthening the immune system through antibody-mediated cellular toxicity, tumor-specific immunity, and adaptive immune responses. However, the development of upfront and acquired resistance poses substantial challenges in maximizing the effectiveness of these therapeutics, necessitating a deeper understanding of the underlying mechanisms. These mechanisms of resistance include antigen loss, derangements in ADC internalization and recycling, drug clearance, and alterations in signaling pathways and the payload target. To overcome resistance, ongoing research and development efforts are focused on urgently identifying biomarkers, integrating immune therapy approaches, and designing novel cytotoxic payloads. This Review provides an overview of the mechanisms and clinical effectiveness of ADCs, and explores their unique immune-boosting function, while also highlighting the complex resistance mechanisms and safety challenges that must be addressed. A continued focus on how ADCs impact the tumor microenvironment will help to identify new payloads that can improve patient outcomes.

A phase Ib trial of pembrolizumab plus paclitaxel or flat-dose capecitabine in 1st/2nd line metastatic triple-negative breast cancer.

Chemoimmunotherapy with anti-programmed cell death 1/ligand 1 and cytotoxic chemotherapy is a promising therapeutic modality for women with triple-negative breast cancer, but questions remain regarding optimal chemotherapy backbone and biomarkers for patient selection. We report final outcomes from a phase Ib trial evaluating pembrolizumab (200 mg IV every 3 weeks) with either weekly paclitaxel (80 mg/m2 weekly) or flat-dose capecitabine (2000 mg orally twice daily for 7 days of every 14-day cycle) in the 1st/2nd line setting. The primary endpoint is safety (receipt of 2 cycles without grade III/IV toxicities requiring discontinuation or ≥21-day delays). The secondary endpoint is efficacy (week 12 objective response). Exploratory aims are to characterize immunologic effects of treatment over time, and to evaluate novel biomarkers. The trial demonstrates that both regimens meet the pre-specified safety endpoint (paclitaxel: 87%; capecitabine: 100%). Objective response rate is 29% for pembrolizumab/paclitaxel (n = 4/13, 95% CI: 10-61%) and 43% for pembrolizumab/capecitabine (n = 6/14, 95% CI: 18-71%). Partial responses are observed in two subjects with chemo-refractory metaplastic carcinoma (both in capecitabine arm). Both regimens are associated with significant peripheral leukocyte contraction over time. Response is associated with clinical PD-L1 score, non-receipt of prior chemotherapy, and the H&E stromal tumor-infiltrating lymphocyte score, but also by a novel 27 gene IO score and spatial biomarkers (lymphocyte spatial skewness). In conclusion, pembrolizumab with paclitaxel or capecitabine is safe and clinically active. Both regimens are lymphodepleting, highlighting the competing immunostimulatory versus lymphotoxic effects of cytotoxic chemotherapy. Further exploration of the IO score and spatial TIL biomarkers is warranted. The clinical trial registration is NCT02734290.

Incidence and prognostic impact of HER2-positivity loss after dual HER2-directed neoadjuvant therapy for HER2+ breast cancer.

BACKGROUND: Loss of HER2 "positivity" can occur in patients with residual disease after neoadjuvant treatment, but the incidence of HER2-positivity loss after neoadjuvant dual HER2-targeted treatment plus chemotherapy, the current standard-of-care for most early stage HER2-positive breast cancers, is not well described. Previous studies that report the HER2 discordance rate after neoadjuvant treatment also do not include the novel HER2-low category. In this retrospective study, we determine the incidence and prognostic impact of HER2-positivity loss, including the evolution to HER2-low disease, after neoadjuvant dual HER2-targeted therapy with chemotherapy. METHODS: Clinicopathologic data for patients with stage I-III HER2+ breast cancer diagnosed between 2015 and 2019 were reviewed in this single institution retrospective study. Patients who received dual HER2-targeted treatment with chemotherapy were included, and HER2 status before and after neoadjuvant therapy was interrogated. RESULTS: A total of 163 female patients were included in the analysis with a median age of 50 years. A pathologic complete response (pCR as defined by ypT0/is) was achieved in 102 (62.5%) of 163 evaluable patients. Among the 61 patients with residual disease after neoadjuvant therapy, 36 (59.0%) had HER2-positive and 25 (41.0%) had HER2-negative residual disease. Of the 25 patients with HER2-negative residual disease, 22 (88%) of patients were classified as HER2-low. After a median follow-up of 3.3 years, patients who retained HER2-positivity after neoadjuvant treatment had a 3-year IDFS rate of 91% (95% CI, 91%-100%), while patients who lost HER2-positivity had a 3-year IDFS rate of 82% (95% CI, 67%-100%). CONCLUSION: Almost half of patients with residual disease following neoadjuvant dual HER2-targeted therapy plus chemotherapy lost HER2-positivity. The loss of HER2-positivity may not confer negative prognostic impact, although the results were limited by short follow-up time. Further research on the HER2 status after neoadjuvant treatment may help guide treatment decisions in the adjuvant setting.

Organoid generation from mouse mammary tumors captures the genetic heterogeneity of clinically relevant copy number alterations.

Breast cancer metastases exhibit many different genetic alterations, including copy number amplifications. Using publicly available datasets, we identify copy number amplifications in metastatic breast tumor samples and using our organoid-based metastasis assays, and we validate FGFR1 is amplified in collectively migrating organoids. Because the heterogeneity of breast tumors is increasingly becoming relevant to clinical practice, we demonstrate our organoid method captures genetic heterogeneity of individual tumors.

Risk-reducing mastectomy decisions among women with mutations in high- and moderate- penetrance breast cancer susceptibility genes.

BACKGROUND: Women harboring mutations in breast cancer susceptibility genes are at increased lifetime risk of developing breast cancer and are faced with decisions about risk management, including whether to undergo high-risk screening or risk-reducing mastectomy (RRM). National guidelines recommend BRCA1 or BRCA2 mutation carriers consider RRM, but that carriers of moderate penetrance mutations (e.g., ATM or CHEK2) should be managed based on family history. We aimed to investigate determinants of decision for RRM, and hypothesized that mutation status, age, family history, partner status, and breast cancer would impact RRM decision making. METHODS: We performed a retrospective study assessing RRM decisions for 279 women. RESULTS: Women with BRCA and moderate penetrance gene mutations, a personal history of breast cancer, or a first degree relative with a history of breast cancer were more likely to undergo RRM. Breast cancer status and age showed an interaction effect such that women with breast cancer were less likely to undergo RRM with increasing age. CONCLUSION: Although national guidelines do not recommend RRM for moderate penetrance carriers, the rates of RRM for this population approached those for BRCA mutation carriers. Further insights are needed to better support RRM decision-making in this population.

Brain radiotherapy, tremelimumab-mediated CTLA-4-directed blockade +/- trastuzumab in patients with breast cancer brain metastases.

Breast cancer brain metastases (BCBM) are a common and devastating complication of metastatic breast cancer with conventional systemic therapies demonstrating limited effectiveness. Consequently, radiotherapy (RT) ± surgery remains the cornerstone of BCBM management. Because preclinical and clinical evidence indicate that immune checkpoint blockade (ICB) may synergize with RT to promote systemic tumor regression, we explored the safety and efficacy of RT and concurrent tremelimumab-mediated cytotoxic T-lymphocyte associated protein 4 (CTLA-4) ICB with tremelimumab ± HER2-directed therapy with trastuzumab for BCBM. Eligible patients had BCBM indicated for brain RT. A Simon two-stage design was adopted to evaluate the efficacy of tremelimumab and RT in 20 patients with human epidermal growth factor receptor normal (HER2-) BCBM. The safety of concurrent RT, tremelimumab, and trastuzumab was evaluated in a cohort of 6 HER2+ patients. The primary endpoint was 12-week non-central nervous system (CNS) disease control rate (DCR). Secondary endpoints included safety, survival, and CNS response. Exploratory correlatives included characterization of peripheral blood immune responses among exceptional responders. Tremelimumab plus RT ± trastuzumab was tolerated with no treatment-related grade 4 adverse events reported. The 12-week non-CNS DCR was 10% (2/20) in the HER2- cohort and 33% (2/6) in the HER2+ cohort. One patient with HER2+ disease experienced a durable partial response with evidence of peripheral T-cell activation. Thus, tremelimumab and RT ± trastuzumab was tolerated. Although modest clinical activity was observed in the HER2- efficacy cohort, encouraging responses were observed in the HER2+ safety cohort. Consequently, a trial to determine efficacy in HER2+ BCBM is planned.Clinical Trial Registration Number: NCT02563925.

Event-free Survival with Pembrolizumab in Early Triple-Negative Breast Cancer.

BACKGROUND: The addition of pembrolizumab to neoadjuvant chemotherapy led to a significantly higher percentage of patients with early triple-negative breast cancer having a pathological complete response (defined as no invasive cancer in the breast and negative nodes) at definitive surgery in an earlier analysis of this phase 3 trial of neoadjuvant and adjuvant therapy. The primary results regarding event-free survival in this trial have not been reported. METHODS: We randomly assigned, in a 2:1 ratio, patients with previously untreated stage II or III triple-negative breast cancer to receive neoadjuvant therapy with four cycles of pembrolizumab (at a dose of 200 mg) or placebo every 3 weeks plus paclitaxel and carboplatin, followed by four cycles of pembrolizumab or placebo plus doxorubicin-cyclophosphamide or epirubicin-cyclophosphamide. After definitive surgery, patients received adjuvant pembrolizumab (pembrolizumab-chemotherapy group) or placebo (placebo-chemotherapy group) every 3 weeks for up to nine cycles. The primary end points were pathological complete response (the results for which have been reported previously) and event-free survival, defined as the time from randomization to the date of disease progression that precluded definitive surgery, local or distant recurrence, occurrence of a second primary cancer, or death from any cause. Safety was also assessed. RESULTS: Of the 1174 patients who underwent randomization, 784 were assigned to the pembrolizumab-chemotherapy group and 390 to the placebo-chemotherapy group. The median follow-up at this fourth planned interim analysis (data cutoff, March 23, 2021) was 39.1 months. The estimated event-free survival at 36 months was 84.5% (95% confidence interval [CI], 81.7 to 86.9) in the pembrolizumab-chemotherapy group, as compared with 76.8% (95% CI, 72.2 to 80.7) in the placebo-chemotherapy group (hazard ratio for event or death, 0.63; 95% CI, 0.48 to 0.82; P<0.001). Adverse events occurred predominantly during the neoadjuvant phase and were consistent with the established safety profiles of pembrolizumab and chemotherapy. CONCLUSIONS: In patients with early triple-negative breast cancer, neoadjuvant pembrolizumab plus chemotherapy, followed by adjuvant pembrolizumab after surgery, resulted in significantly longer event-free survival than neoadjuvant chemotherapy alone. (Funded by Merck Sharp and Dohme, a subsidiary of Merck; KEYNOTE-522 ClinicalTrials.gov number, NCT03036488.).

Current and future landscape of targeted therapy in HER2-positive advanced breast cancer: redrawing the lines.

BACKGROUND: Evidence to date supports continued human epidermal growth factor receptor 2 (HER2) suppression beyond progression on HER2-directed therapy for advanced HER2-positive breast cancer. Data from several phase II and III trials evaluating HER2-directed therapy following second-line T-DM1 have recently become available. METHODS: We performed a systematic search of the published and presented literature to identify phase II and phase III trials assessing novel HER2-targeted agents as third-line therapy or beyond for HER2-positive advanced breast cancer using search terms 'breast cancer' AND 'HER2' AND 'advanced' AND ('phase II' OR 'phase III'). RESULTS: Eight clinical trials reporting efficacy outcomes on third-line or greater HER2-directed therapy for HER2-positive advanced breast cancer were identified. In phase III trials, margetuximab and neratinib combinations demonstrated significant 1.3-month (hazard ratio, HR = 0.71, p < 0.001) and 0.1-month (HR = 0.76, p = 0.006) net improvements in median progression-free survival (PFS), respectively, with no significant improvements in overall survival (OS). Tucatinib added to trastuzumab and capecitabine demonstrated a significant 2.7-month improvement in median PFS (HR = 0.57, p < 0.00001) and a 5.5-month improvement in median OS (HR = 0.73, p = 0.004) in a randomized phase II trial, including significant clinical benefit for patients with brain metastases. Finally, trastuzumab-deruxtecan, zenocutuzumab, and poziotinib demonstrated benefit in phase II trials with the most robust overall response rate (62.0%) and median duration of response (18.2 months) observed for trastuzumab-deruxtecan among heavily pretreated patients. CONCLUSION: Tucatinib plus trastuzumab and capecitabine significantly prolongs OS, and promising preliminary response outcomes for trastuzumab-deruxtecan suggest that sequencing of these regimens following second-line therapy is reasonable.

Changes in T-cell subsets and clonal repertoire during chemoimmunotherapy with pembrolizumab and paclitaxel or capecitabine for metastatic triple-negative breast cancer.

BACKGROUND: Chemoimmunotherapy is a standard treatment for triple-negative breast cancer (TNBC), however, the impacts of different chemotherapies on T-cell populations, which could correlate with clinical activity, are not known. Quantifying T-cell populations with flow cytometry and T-cell receptor (TCR) immunosequencing may improve our understanding of how chemoimmunotherapy affects T-cell subsets, and to what extent clonal shifts occur during treatment. TCR immunosequencing of intratumoral T cells may facilitate the identification and monitoring of putatively tumor-reactive T-cell clones within the blood. METHODS: Blood and tumor biopsies were collected from patients with metastatic TNBC enrolled in a phase Ib clinical trial of first or second-line pembrolizumab with paclitaxel or capecitabine. Using identical biospecimen processing protocols, blood samples from a cohort of patients treated for early-stage breast cancer were obtained for comparison. Treatment-related immunological changes in peripheral blood and intratumoral T cells were characterized using flow cytometry and TCR immunosequencing. Clonal proliferation rates of T cells were compared based on intratumoral enrichment. RESULTS: When combined with pembrolizumab, paclitaxel and capecitabine resulted in similar time-dependent lymphodepletions across measured peripheral T-cell subsets. Their effects were more modest than that observed following curative-intent dose-dense anthracycline and cyclophosphamide (ddAC) (average fold-change in CD3+ cells, capecitabine: -0.42, paclitaxel: -0.56, ddAC: -1.21). No differences in T-cell clonality or richness were observed following capecitabine or paclitaxel-based treatments. Regression modeling identified differences in the emergence of novel T-cell clones that were not detected at baseline (odds compared with ddAC, capecitabine: 0.292, paclitaxel: 0.652). Pembrolizumab with paclitaxel or capecitabine expanded T-cell clones within tumors; however, these clones did not always expand within the blood. Proliferation rates within the blood were similar between clones that were enriched and those that were not enriched within tumors. CONCLUSION: Chemoimmunotherapy for metastatic TNBC with pembrolizumab and capecitabine or paclitaxel resulted in similar peripheral T-cell subset lymphodepletion without altering T-cell clonal diversity. Regression modeling methods are applicable in immune monitoring studies, such as this to identify the odds of novel T-cell clones emerging during treatment, and proliferation rates of tumor-enriched T-cell clones.

Current advances in immune checkpoint inhibitor combinations with radiation therapy or cryotherapy for breast cancer.

PURPOSE: Immune checkpoint inhibition (ICI) has demonstrated clinically significant efficacy when combined with chemotherapy in triple negative breast cancer (TNBC). Although many patients derived benefit, others do not respond to immunotherapy, therefore relying upon innovative combinations to enhance response. Local therapies such as radiation therapy (RT) and cryotherapy are immunogenic and potentially optimize responses to immunotherapy. Strategies combining these therapies and ICI are actively under investigation. This review will describe the rationale for combining ICI with targeted local therapies in breast cancer. METHODS: A literature search was performed to identify pre-clinical and clinical studies assessing ICI combined with RT or cryotherapy published as of August 2021 using PubMed and ClinicalTrials.gov. RESULTS: Published studies of ICI with RT and IPI have demonstrated safety and signals of early efficacy. CONCLUSION: RT and cryotherapy are local therapies that can be integrated safely with ICI and has shown promise in early trials. Randomized phase II studies testing both of these approaches, such as P-RAD (NCT04443348) and ipilimumab/nivolumab/cryoablation for TNBC (NCT03546686) are current enrolling. The results of these studies are paramount as they will provide long term data on the safety and efficacy of these regimens.

Society for Immunotherapy of Cancer (SITC) clinical practice guideline on immunotherapy for the treatment of breast cancer.

Breast cancer has historically been a disease for which immunotherapy was largely unavailable. Recently, the use of immune checkpoint inhibitors (ICIs) in combination with chemotherapy for the treatment of advanced/metastatic triple-negative breast cancer (TNBC) has demonstrated efficacy, including longer progression-free survival and increased overall survival in subsets of patients. Based on clinical benefit in randomized trials, ICIs in combination with chemotherapy for the treatment of some patients with advanced/metastatic TNBC have been approved by the United States (US) Food and Drug Administration (FDA), expanding options for patients. Ongoing questions remain, however, about the optimal chemotherapy backbone for immunotherapy, appropriate biomarker-based selection of patients for treatment, the optimal strategy for immunotherapy treatment in earlier stage disease, and potential use in histological subtypes other than TNBC. To provide guidance to the oncology community on these and other important concerns, the Society for Immunotherapy of Cancer (SITC) convened a multidisciplinary panel of experts to develop a clinical practice guideline (CPG). The expert panel drew upon the published literature as well as their clinical experience to develop recommendations for healthcare professionals on these important aspects of immunotherapeutic treatment for breast cancer, including diagnostic testing, treatment planning, immune-related adverse events (irAEs), and patient quality of life (QOL) considerations. The evidence-based and consensus-based recommendations in this CPG are intended to give guidance to cancer care providers treating patients with breast cancer.