Several first-line (1L) treatments have been evaluated for patients with metastatic triple-negative breast cancer (mTNBC) ineligible for anti-PD-(L)1 inhibitors, but the optimal approach remains unclear. We conducted a systematic review and trial-level frequentist network meta-analysis of randomized controlled trials evaluating 1L therapies for mTNBC not eligible for anti-PD-(L)1 inhibitors (PROSPERO: CRD420251177761). Progression-free survival (PFS) was the primary endpoint. Ten trials (n = 3,752) were included. Treatments comprised antibody-drug conjugates (ADCs), bevacizumab+chemotherapy (CT), immune-checkpoint inhibitors + CT, and PARP inhibitors (PARPi). Excluding PARPi, datopotamab-deruxtecan (Hazard Ratio [HR] 0.57), sacituzumab-govitecan (HR 0.62), and bevacizumab + CT (HR 0.64) significantly improved PFS versus CT, with no significant differences between ADCs or versus bevacizumab + CT. Dato-DXd also improved overall survival and achieved the highest response rate. In patients with germline (g) BRCA 1/2-mutated disease, PARPi ranked among the most effective treatments. Toxicities varied by regimen. ADCs and bevacizumab + CT appear preferred 1L options, whereas PARPi remain valuable for g BRCA 1/2-mutated disease.

Abstract Purpose: The phosphoinositide 3-kinase (PI3K)/AKT serine/threonine kinase (AKT) pathway is frequently activated in hormone receptor (HR)-positive/human epidermal growth factor receptor 2 (HER2)-negative advanced breast cancer, with loss of phosphatase and tensin homolog (PTEN) activity contributing to this activation. Capivasertib is a potent pan-AKT inhibitor, approved in combination with fulvestrant for the treatment of HR-positive/HER2-negative locally advanced/metastatic breast cancer with one or more PIK3CA/AKT1/PTEN tumor alterations. Next-generation sequencing (NGS) is commonly used to identify patients with PIK3CA/AKT1/PTEN tumor alterations. However, the utility of immunohistochemistry (IHC) to identify patients with PTEN-deficient tumors has not been explored in this context. Experimental Design: This exploratory analysis was based on tumor samples collected from patients in the global phase III CAPItello-291 study. Results: PTEN IHC results were obtained for 367 tumor samples, with 70 (19.1%) identified as PTEN deficient by IHC. A total of 346 (94.3%) samples with a PTEN IHC test result also had NGS test results available for PIK3CA/AKT1/PTEN alteration status. When comparing PTEN deficiency by IHC with PTEN alteration status by NGS, the overall, positive, and negative percent agreements were 87.0% (301/346), 71.9% (23/32), and 88.5% (278/314), respectively. Exploratory analysis in patients with PTEN-deficient tumors by IHC (n = 70) showed improved progression-free survival in the capivasertib plus fulvestrant versus placebo plus fulvestrant treatment arm (median 9.3 vs. 3.7 months; hazard ratio: 0.52, 95% confidence interval, 0.28–0.90). Conclusions: These results suggest potential utility for IHC in determining tumor PTEN status in breast cancer and raise the possibility of IHC identifying additional patients who could benefit from treatment with capivasertib and fulvestrant.

Background In KEYNOTE-522 (NCT03036488), addition of perioperative pembrolizumab to neoadjuvant chemotherapy significantly improved pathological complete response (pCR), event-free survival (EFS), and overall survival (OS) in early-stage triple-negative breast cancer (TNBC). pCR and EFS results in participants enrolled in Asia were consistent with those in the overall population. We report OS, updated EFS, and safety outcomes in participants enrolled in Asia. Methods Participants with newly diagnosed, high-risk, early-stage TNBC (T1c [N1‒N2] or T2‒T4 [N0‒N2] per AJCC 7th edition) were randomized 2:1 to 8 cycles of neoadjuvant pembrolizumab 200 mg Q3W or placebo plus chemotherapy. After definitive surgery, participants received adjuvant pembrolizumab 200 mg Q3W or placebo for ≤9 cycles. Primary endpoints were pCR (ypT0/Tis ypN0) and EFS. OS was a secondary endpoint. Results Of 1174 randomized participants, 216 were enrolled in Asia. At data cutoff (March 22, 2024), EFS events occurred in 18/136 participants (13.2%) in the pembrolizumab+chemotherapy group versus 22/80 (27.5%) in the placebo+chemotherapy group (HR, 0.43 [95% CI, 0.23‒0.81]); 60-month EFS rates (95% CIs) were 87.4% (80.6%‒92.0%) and 72.1% (60.7%‒80.6%), respectively. In the respective groups, 12/136 (8.8%) and 16/80 participants (20.0%) died (HR, 0.41 [95% CI, 0.19‒0.86]); 60-month OS rates (95% CIs) were 91.9% (85.8%‒95.4%) and 81.1% (70.5%‒88.1%). Treatment-related AEs led to treatment discontinuation in 19/136 participants (14.0%) with pembrolizumab+chemotherapy and 7/79 (8.9%) with placebo+chemotherapy. Conclusions OS and updated EFS outcomes in KEYNOTE-522 participants enrolled in Asia were consistent with those in the overall population and support use of perioperative pembrolizumab+neoadjuvant chemotherapy as a standard-of-care treatment in this setting.

Carcinosarcomas (CSs) are aggressive biphasic tumors characterized by epithelial and mesenchymal components, whose histogenesis and differentiation dynamics remain poorly understood. We present single-nucleus RNA sequencing (snRNA-seq) analysis of six CSs (five endometrial and one ovarian) and two normal endometrial samples, profiling over 96,298 cells. By integrating transcriptomic data with inferred copy number variations (CNVs), immunohistochemistry (IHC), fluorescence in situ hybridization (FISH), and in situ hybridization (ISH) validation, we resolved the complex cellular architecture of these tumors, identified lineage-specific programs, and revealed unexpected differentiation trajectories. snRNA-seq was used to further refine the histopathological classification of three cases by uncovering heterologous differentiation not previously recognized: one rhabdomyogenic, one osteogenic, and, notably, one exhibiting a novel tenogenic program, defined by the expression of SCX, MKX, and TNMD. All CSs displayed a prominent mesenchymal compartment comprising both undifferentiated fibroblast-like cells and distinct lineage committed populations, including rhabdomyoblasts (Rhab), tenoblasts (Teno), osteoblasts (Osteo), and chondroblasts (Chond). In some tumors, multiple mesenchymal identities co-existed, and in others, differentiation gradients (e.g. immature versus mature rhabdomyoblasts) were observed. These patterns underscore the cellular plasticity and multilineage potential of the sarcomatous component. Furthermore, the expression of specialized interface markers (COL22A1, NCAM1, ACAN, CHRNG, MUSK) suggests that some tumors use structured developmental programs reminiscent of the muscle-tendon junction, enthesis, or neuromuscular junction. CNV analysis revealed tumor-specific genomic alterations with clonal and subclonal patterns linked to differentiation state, which were validated by FISH. Altogether, this study demonstrates that CSs are not static biphasic tumors but rather complex ecosystems with extensive developmental plasticity. Our findings redefine their classification and support the use of single-nucleus approaches to uncover hidden differentiation trajectories in highly heterogeneous cancers, including the discovery of a previously unreported tenogenic lineage. Our results challenge the diagnosis of homologous CS when only morphological criteria are applied. © 2026 The Author(s). The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

The anti-tumour immune response plays a pivotal role in eliminating tumour cells, with the presence of tumour-infiltrating lymphocytes (TILs) often correlated with improved patient outcomes. Among these, CD4+ T lymphocytes act as key orchestrators of the immune response, functioning as effector and regulatory cells, and are essential for establishing immunological memory. To better understand the role of CD4+ T cells in anti-tumour immunity, we analysed the HLA-II immunopeptidome of dendritic cells (DCs) from HLA-heterozygous donors pulsed with a protein extract from the MCF-7 tumour cell line. Our objective was to identify differences in the arrays of peptides binding distinct HLA-DRB1 allele combinations and the effect of DC pulsing on peptide presentation. We found that presented peptide repertoires are strongly influenced by HLA-DR heterozygosity in an allele-specific manner. Alleles with high binding strength (e.g., DRB1*01:01, DRB1*03:01 and DRB1*04:04) tended to dominate peptide presentation; however, this dominance is significantly modulated by the allelic combination, suggesting that antigen presentation is shaped not only by individual allele properties but also by their combinations. Pulsing DCs with MCF-7 extracts increased peptide overlap between donors and enabled the identification of 58 proteins putatively derived from the tumour cell line lysates. Interestingly, peptide presentation from these proteins reinforced allele-specific features of dominance and weakness previously observed across the entire immunopeptidome. Gaining insights into the peptide repertoire presented by distinct HLA-DR combinations could inform the design of personalised immunotherapies based on peptide-pulsed DCs, ultimately enhancing CD4+ TIL responses across diverse patient populations.

1014 Background: SG demonstrated significant and clinically meaningful progression-free survival (PFS) improvement vs chemo in pts with previously untreated, locally advanced unresectable or metastatic TNBC who were not candidates for PD-(L)1i in ASCENT-03 (NCT05382299). We report preplanned exploratory efficacy analyses in ASCENT-03 by Trop-2 expression, BRCA status, and HER2 expression. Methods: 588 pts randomized 1:1 to SG or chemo (taxane or gemcitabine + carboplatin). Trop-2 expression was measured by immunohistochemistry (IHC), tumor BRCA (tBRCA) status by whole exome sequencing, and HER2 expression by in situ hybridization (ISH) and IHC, all in centrally tested tumor samples (fresh or archival; 43% from metastatic sites). Pts were subgrouped by Trop-2 expression quartile, tBRCA wild-type (WT) or mutant (mut; mut in BRCA1, BRCA2, or both) status, and HER2 status (IHC 0 vs Low [IHC 1+ or IHC 2+/ISH-]). Biomarker status was analyzed to determine association with PFS by blinded independent central review (BICR). Other efficacy outcomes by biomarker status will be presented. Results: Median Trop-2 H-score: 240; H-scores by quartile (Q): Q1 0-184, Q2 185-239, Q3 240-283, Q4 284-300. Trop-2 expression was available in 499 pts. PFS by BICR was longer with SG vs chemo in all Trop-2 expression quartiles (Table). Hazard ratio (HR; 95% confidence interval [CI]) was 0.54 (0.35-0.84) in Q1, 0.62 (0.40-0.97) in Q2, 0.84 (0.54-1.31) in Q3, and 0.60 (0.38-0.95) in Q4. tBRCA status was available in 423 pts; proportion of pts with tBRCA mutations was comparable between treatment groups (~18%). PFS was longer with SG vs chemo in tBRCA WT and mut subgroups, with HR (95% CI) 0.70 (0.54-0.92) in tBRCA WT and 0.59 (0.32-1.09) in tBRCA mut. HER2 status was available in 551 pts; PFS was longer with SG vs chemo in both HER2 subgroups. HR was 0.63 (0.46-0.85) in the IHC 0 subgroup and 0.74 (0.55-1.01) in the HER2 Low subgroup. Conclusions: PFS was longer with SG vs chemo across all Trop-2 categories, tBRCA genotypes, and HER2 subgroups. These results reinforce the significant, clinically meaningful benefit of SG as first-line treatment for pts in this population across multiple biomarker subgroups. Clinical trial information: NCT05382299 . Efficacy, BICR N Median PFS (95% CI), months Biomarker Subgroup SG Chemo SG Chemo HR (95% CI) Trop-2(n = 499) Q1 68 55 8.5(5.6-12.7) 5.5(4.2-8.1) 0.54(0.35-0.84) Q2 60 62 8.3(5.6-12.4) 6.8(4.2-9.0) 0.62(0.40-0.97) Q3 50 74 9.7(7.6-11.3) 7.0(5.3-8.5) 0.84(0.54-1.31) Q4 74 56 9.9(6.9-NR) 8.1(4.4-8.5) 0.60(0.38-0.95) tBRCA(n = 423) WT 177 169 8.8(7.2-9.9) 6.9(5.4-8.3) 0.70(0.54-0.92) Mut 40 37 12.7(7.2-18.7) 8.3(5.6-11.2) 0.59(0.32-1.09) HER2(n = 551) IHC 0 115 138 8.3(6.9-10.3) 5.6(4.3-7.0) 0.63(0.46-0.85) Low 159 139 9.8(8.3-12.4) 8.3(5.7-9.7) 0.74(0.55-1.01)

Patients with advanced TNBC with PD-L1 CPS < 10 are typically treated with chemotherapy and experience poor outcomes. Sacituzumab tirumotecan (sac-TMT; MK-2870/SKB264) is a trophoblast cell-surface antigen 2 (TROP2)-directed antibody-drug conjugate with a unique, bifunctional linker that maximizes payload delivery to tumor cells. Combining sac-TMT with immunotherapy may improve outcomes given their complementary respective direct cytotoxic and immune-mediated antitumor effects regardless of tumor PD-L1 expression. The TroFuse-011 study evaluates sac-TMT with/without pembrolizumab versus treatment of physician's choice (TPC; paclitaxel, nab-paclitaxel, or gemcitabine plus carboplatin) in previously untreated, centrally confirmed, locally recurrent unresectable or metastatic TNBC with PD-L1 CPS <10. Eligible adults with measurable disease per RECIST version 1.1, ECOG PS 0/1, and tumor tissue sample for central PD-L1 and TROP2 testing will be randomized to receive sac-TMT (arm A), sac-TMT plus pembrolizumab (arm B), or TPC (arm C). Primary endpoints include progression-free survival (PFS; arm A vs C and arm B vs C) and overall survival (OS; arm A vs C). Secondary endpoints include PFS (arm B vs A), OS (arm B vs C and arm B vs A), objective response rate (arm A vs C and arm B vs C), duration of response, patient-reported outcomes, and safety. Enrollment is ongoing.Clinical trial registration: www.clinicaltrials.gov identifier is NCT06841354.

Antibody-drug conjugates are redefining treatment options in advanced breast cancer, demonstrating efficacy across all breast cancer subtypes. However, their rapid clinical expansion has resulted in several unresolved challenges, including the need for rational sequencing strategies, appropriate and ethical trial design, drug tolerability, and the limitation of mono-national development programs.

Hereditary breast cancer (BC) remains unexplained in a substantial proportion of families who test negative for BRCA1/2 and other known susceptibility genes. To contribute to the genomic characterization of these unresolved cases, we generated a whole-genome sequencing (WGS) dataset from six women belonging to two unrelated high-risk families, each comprising three sisters diagnosed with BC. All participants had previously received negative results in conventional multigene panel testing. WGS was performed on peripheral blood DNA using the Illumina NovaSeq platform, followed by variant calling against GRCh38 and the comprehensive annotation of single-nucleotide variants, indels, and structural variants. For each family, we identified shared ClinVar-annotated variants, rare exonic or splice-site alterations, and intronic variants located within a curated set of 286 cancer-related genes. The dataset includes per-patient VCF files, copy number variation annotations, and family-level variant summaries. Raw and processed data are publicly available through the Sequence Read Archive and Zenodo. This resource supports variant reinterpretation, exploration of regulatory and intronic regions, and methodological benchmarking in the study of familial BC beyond established susceptibility genes.

Abstract Background: Disease progression in pts with ER+/HER2- mBC on 1L ET + CDK4/6i is associated with mechanisms of resistance that impact the efficacy of subsequent therapy. Ela improved PFS vs SOC ET (ESR1m tumors HR 0.55; 95% CI 0.39-0.77; all pts HR 0.70; 95% CI 0.55-0.88) with manageable safety in the Ph3 EMERALD trial (Bidard 2022). ELEVATE is evaluating Ela combined with Eve, alpelisib, capivasertib, Abema, ribociclib, or palbociclib to address resistance mechanisms. Based on encouraging Ph1b results, we evaluated Ph2 combinations of Ela + Eve or Abema in all pts and subgroups. Methods: Pts with ER+/HER2- mBC, 1-2L of prior ET are eligible regardless of ESR1m status. Prior CDK4/6i is required for Arm B (Ela + Eve) and Arm C (Eve + Abema). Pts with no prior CDK4/6i were enrolled in Arm D (Ela + Abema). Ph2 evaluates PFS with each combination. ESR1 and PIK3CA mutation status were evaluated in pts for both combinations Ela + Eve (n=48) and Ela + Abema (n=50). Results: As of Sept 2025, 50 pts enrolled in Arm B (Ela + Eve), and 60 enrolled in Arms C and D (Ela + Abema combinations, n=30 each). Baseline characteristics are pts with visceral mets (72% Arm B, 92% Arms C/D), primary ET resistance (20% Arm B, 15% Arms C/D), ESR1m (42% Arm B, 33% Arms C/D), and PIK3CAm (50% Arm B, 27% Arms C/D). PFS was consistent across subgroups (Table 1). Safety results were consistent with the known profiles of Eve or Abema + SOC ET. Ph2 Ela + Eve ORR was 19.5%, DCR 82.9%, mDOR 8.54 mo. Ph2 Ela + Abema ORR was 24.6%, DCR 91.2%, mDOR 14.75 mo. Conclusion: Ela combinations show a consistent clinically meaningful PFS irrespective of ESR1m status in pts with ER+/HER2- mBC after progressive disease on ET ± prior CDK4/6i, and could become an ET backbone for combination strategies, supporting an all-oral approach. Citation Format: Hope S. Rugo, Sara M. Tolaney, Nancy Chan, Giuliano Borges, Rinat Yerushalmi, Marina N. Sharifi, Wassim McHayleh, Thaddeus Beck, Neelima Vidula, Erika Hamilton, Kristine J. Rinn, Joyce O’Shaughnessy, Giuseppe Curigliano, Javier Cortés, Paula Muñoz Romero, Giulia Tonini, Alessandro Paoli, Monica Binaschi, Li Cheng, Jennifer A. Crozier, Tomer Wasserman, Virginia Kaklamani. Elacestrant (Ela) in combination with everolimus (Eve) or abemaciclib (Abema) in patients with ER+/HER2- locally advanced or metastatic breast cancer mBC: phase 2 results from ELEVATE, an open-label, umbrella study [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(8_Suppl):Abstract nr CT262.

Triple-negative breast cancer is an aggressive and heterogeneous breast cancer subtype for which immune checkpoint inhibitors combined with chemotherapy have improved outcomes in selected patients. However, primary and acquired resistance remain common, underscoring the need to identify extrinsic, modifiable determinants of antitumor immunity. Increasing evidence indicates that the gut and tumor-associated microbiota shape systemic and intratumoral immune tone and influence the efficacy of cancer therapies. Beyond microbial composition, microbiota-derived metabolites-including short-chain fatty acids, indole-tryptophan derivatives, bile acids, polyamines, and other small molecules-can act as functional mediators linking microbial ecology to immune-cell programming and tumor biology. These metabolites modulate dendritic cell function, T-cell priming and fitness, myeloid polarization, inflammatory set points, and metabolic pathways within the tumor microenvironment, thereby potentially enhancing or constraining responses to chemoimmunotherapy. Importantly, while some studies propose intratumoral microbial effects, most clinically actionable evidence currently supports systemic gut-derived metabolites and immune tone modulation that secondarily shapes the TNBC tumor microenvironment. In this review, we synthesize current knowledge on (i) the immunobiology of triple-negative breast cancer (TNBC) relevant to microbiota-driven modulation, (ii) mammary and gut microbiome features reported in TNBC, and (iii) mechanistic pathways through which microbial metabolites may regulate antitumor immunity and immune checkpoint inhibitors (ICI) sensitivity. We also discuss methodological considerations for integrating microbiome profiling with metabolomics and immune phenotyping and evaluate emerging opportunities to leverage microbiota-derived metabolites as biomarkers and therapeutic targets. Finally, we highlight translational strategies-including diet, pre/probiotics, antibiotic stewardship, fecal microbiota transplantation, and metabolite-centric ("postbiotic") approaches-and outline priorities for TNBC-focused, prospective multi-omics studies to move from associative signatures toward actionable interventions.

Neoadjuvant chemotherapy is standard for stage IB-III triple-negative breast cancer (TNBC), with pathological complete response (pCR) strongly associated with survival. Although escalation with platinum and immune checkpoint inhibitors (ICI) improves pCR and long-term outcomes, patients with pCR in control arms of pivotal trials also show favorable outcomes. Whether the regimen leading to pCR impacts long-term survival is largely unknown. We conducted a systematic review and meta-analysis, searching phase II and III trials including early-stage TNBC patients with pCR. A pooled analysis of Kaplan–Meier-derived individual patient data was performed for event-free survival (EFS) and overall survival (OS), with subgroup analyses by treatment regimens. Of 2830 identified publications, 18 trials comprising 3430 patients were included. Neoadjuvant ICI with chemotherapy improved EFS (HR 0.67; 95

PURPOSE:To determine the safety and efficacy of taselisib, a selective PI3K inhibitor, in combination with tamoxifen. PATIENTS AND METHODS:POSEIDON is a phase II, randomized, placebo-controlled trial conducted from June 2016 to March 2020. Eligible patients were refractory upon prior endocrine therapy. Prior treatment with cyclin-dependent kinase 4/6 (CDK4/6) inhibitors and everolimus was allowed. Patients were randomized (1:1) to receive either taselisib (4 mg) + tamoxifen (20 mg) or placebo + tamoxifen. The primary endpoint of the trial was investigator-assessed progression-free survival (PFS) in the intention-to-treat (ITT) population (two-sided α 0.2, 90% power). Exploratory biomarker analysis with regards to prognosis and treatment resistance was conducted in circulating tumor (ct)DNA. RESULTS:POSEIDON met its primary endpoint, in which patients treated with taselisib + tamoxifen had improved PFS compared with patients treated with placebo + tamoxifen in the ITT population (median PFS 4.8 months vs. 3.2 months; stratified hazard ratio 0.69; 80% confidence interval, 0.49-0.98, P = 0.17). However, toxicity of taselisib was significant, with diarrhea (40% any grade) as the most common adverse event. Exploratory analyses indicated that high tumor fraction (TF) determined in ctDNA at baseline is associated with worse PFS and overall survival (P < 0.0001). CONCLUSIONS:Our findings suggest efficacy of PI3K inhibition + tamoxifen beyond second-line treatment and after prior targeted therapies, including CDK4/6 inhibition in metastatic HR+/HER2- breast cancer, although the magnitude of benefit did not outweigh the tolerability of this combination. Exploratory biomarker analysis indicates that TF determined in ctDNA differentiates patients based on prognosis and may help optimize patient selection for targeted treatment strategies.

Circulating tumor DNA (ctDNA) is a tumor-derived, circulating bioanalyte that can be detected in blood using minimally invasive, blood-based biomarker procedures and has prognostic value in early breast cancer. Quantitative features of ctDNA, including baseline detectability and levels, have shown prognostic potential in early breast cancer by reflecting tumor burden and biologic aggressiveness, thereby supporting risk stratification. Post-treatment ctDNA detection may identify minimal residual disease and can precede radiologic or symptomatic recurrence by several months to years. Nevertheless, ctDNA has not yet been adopted in routine clinical practice in early breast cancer, partly because of biologic constraints, including low and heterogeneous tumor DNA shedding, as well as pre-analytical and analytical variability that can affect testing sensitivity. Ongoing efforts are focused on methodological standardization and clarification of the clinically actionable context. This narrative review examines the challenges in applying ctDNA to early breast cancer, spanning patient selection, sampling logistics, specimen handling, assay performance, and sources of assay failure. The authors outline determinants of ctDNA measurement that restrict the proportion of evaluable patients and limit translation to clinical practice and then summarize evidence supporting ctDNA for early response monitoring during neoadjuvant therapy, postoperative minimal residual disease detection, and longitudinal molecular surveillance. Finally, ctDNA-guided therapeutic interception strategies and emerging multimodal cell-free DNA approaches are discussed.

Hormone receptor-positive/HER2-negative breast cancer evolves in response to therapy, demanding smarter, adaptive biomarker-based treatment strategies. We review emerging dynamic biomarkers to guide therapeutic decision-making, spanning tissue and liquid biopsies, metabolic imaging, and microbiome profiling, that capture tumor or host-related changes over time. By contrasting Academic and Industry approaches, we advocate for a cultural shift in clinical trial design and implementation, aiming to move from reactive to proactive Oncology.

We prospectively evaluated surgical outcomes following neoadjuvant pembrolizumab or placebo added to neoadjuvant chemotherapy among participants with early-stage triple-negative breast cancer (TNBC) in the phase 3 KEYNOTE-522 study (NCT03036488). Participants with previously untreated, early-stage TNBC (AJCC stage T1c N1–2 or T2–4 N0–2) were randomized 2:1 to neoadjuvant pembrolizumab/placebo plus paclitaxel-carboplatin for 4 cycles, followed by pembrolizumab/placebo plus doxorubicin/epirubicin and cyclophosphamide for 4 cycles. After definitive surgery, participants received adjuvant pembrolizumab/placebo Q3W for 9 cycles. Surgery type and timing, nodal status postsurgery, and adverse events within 30 days following surgery were recorded. Among 1,174 randomized participants (pembrolizumab plus chemotherapy, n = 784; placebo plus chemotherapy, n = 390), similar proportions underwent breast-conserving surgery (45.2 https://www.clinicaltrials.gov/study/NCT03036488