Addition of pembrolizumab to neoadjuvant chemotherapy followed by adjuvant pembrolizumab improved outcomes in patients with high-risk, early-stage, triple-negative breast cancer. However, whether the addition of neoadjuvant pembrolizumab to chemotherapy would improve outcomes in high-risk, early-stage, estrogen receptor-positive/human epidermal growth factor receptor 2-negative (ER+/HER2−) breast cancer remains unclear. We conducted a double-blind, placebo-controlled phase 3 study (KEYNOTE-756) in which patients with previously untreated ER+/HER2− grade 3 high-risk invasive breast cancer (T1c-2 (≥2 cm), cN1–2 or T3–4, cN0–2) were randomly assigned (1:1) to neoadjuvant pembrolizumab 200 mg or placebo Q3W given with paclitaxel QW for 12 weeks, followed by four cycles of doxorubicin or epirubicin plus cyclophosphamide Q2W or Q3W. After surgery (with/without adjuvant radiation therapy), patients received adjuvant pembrolizumab or placebo for nine cycles plus adjuvant endocrine therapy. Dual primary endpoints were pathological complete response and event-free survival in the intention-to-treat population. In total, 635 patients were assigned to the pembrolizumab−chemotherapy arm and 643 to the placebo−chemotherapy arm. At the study’s prespecified first interim analysis, the pathological complete response rate was 24.3 NCT03725059 . In this prespecified interim analysis of the KEYNOTE-756 phase 3 trial, pembrolizumab and chemotherapy treatment of patients with high-risk, early-stage, estrogen receptor-positive/human epidermal growth factor receptor-negative breast cancer improved the pathological complete response rate compared with chemotherapy alone.

Breast and gynecologic cancers are common across the world and are associated with substantial societal and economic burden. Pembrolizumab was among the first immune checkpoint inhibitors targeting programmed cell death protein 1 to be approved for the treatment of patients with triple-negative breast cancer, cervical cancer, and endometrial cancer. Recent clinical trials have established pembrolizumab regimens as a standard of care treatment for these tumor types. Clinical data are further supported by patient-reported outcome, cost-effectiveness, and real-world evidence. Pembrolizumab monotherapy and combination regimens do not negatively influence health-related quality of life and are cost-effective relative to comparators. Ongoing phase 3 studies with pembrolizumab will expand the current understanding of its use in breast and gynecologic cancers. Several of these studies are in patients with early-stage disease with the hope of curing patients. The main objective of this review is to summarize the clinical, humanistic, and economic value of pembrolizumab in these settings and to describe the future challenges for patients, caregivers, clinicians, and payers.

Small, hormone receptor-positive (HR+), HER2-negative (HER2-), lymph node-negative breast cancers are associated with relatively low rates of disease recurrence and have therefore been underrepresented in clinical trials assessing the effects of systemic therapy. Consequently, it remains uncertain if this patient population derives benefit from these treatments. For this exploratory analysis, we selected MINDACT (NCT00433589) patients with a HR+, HER2-, T1ab (<= 1 cm) tumor and negative lymph nodes. Patients with discordant clinical risk and MammaPrint genomic risk classification were randmomized to receive chemotherapy based on either the clinical or the genomic risk assessment. Endocrine therapy treatment was based on local guidelines. 715/6693 (10.7%) MINDACT patients had HR+, HER2-, T1abN0 breast cancer and were included in this analysis. All were clinically low-risk, 124/715 (17.3%) were genomic high-risk. For genomic high-risk tumors, 8-year distant metastasis-free survival (DMFS) was 92.9% (95% CI 86.2-96.4%) compared to 95.0% (95% CI 92.8-96.6%) for genomic low-risk tumors. For genomic high-risk tumors treated with or without chemotherapy, 8-year DMFS was 89.2% (95% CI 73.6-95.8%) and 94.1% (95% CI 82.9-98.1%), respectively. For genomic low-risk tumors, the 8-year DMFS and disease-free survival (DFS) were 96.1% (95% CI 93.4-97.6%) and 89.3% (95% CI 85.5-92.2%) when treated with endocrine therapy and 92.9% (95% CI 87.9-95.9%) and 79.4% (95% CI 72.5-84.8%) without. In conclusion, although the number of randomized patients is small, patients with small, genomic high-risk breast cancer did not seem to derive benefit from chemotherapy. Endocrine therapy was associated with improved outcomes even in genomic low-risk breast cancers.

BACKGROUND:In patients with early-stage triple-negative breast cancer, the phase 3 KEYNOTE-522 trial showed significant improvements in pathological complete response and event-free survival with the addition of pembrolizumab to platinum-containing chemotherapy. Here we report the final results for overall survival. 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 and event-free survival. Overall survival was a secondary end point. RESULTS:Of the 1174 patients who underwent randomization, 784 were assigned to the pembrolizumab-chemotherapy group and 390 to the placebo-chemotherapy group. At the data-cutoff date (March 22, 2024), the median follow-up was 75.1 months (range, 65.9 to 84.0). The estimated overall survival at 60 months was 86.6% (95% confidence interval [CI], 84.0 to 88.8) in the pembrolizumab-chemotherapy group, as compared with 81.7% (95% CI, 77.5 to 85.2) in the placebo-chemotherapy group (P = 0.002). Adverse events were consistent with the established safety profiles of pembrolizumab and chemotherapy. CONCLUSIONS:Neoadjuvant pembrolizumab plus chemotherapy followed by adjuvant pembrolizumab resulted in a significant improvement, as compared with neoadjuvant chemotherapy alone, in overall survival among patients with early-stage triple-negative breast cancer. (Funded by Merck Sharp and Dohme, a subsidiary of Merck [Rahway, NJ]; KEYNOTE-522 ClinicalTrials.gov number, NCT03036488.).

Additional therapies are needed to improve outcomes in patients with hormone receptor-positive/human epidermal growth factor receptor 2-negative breast cancer. Research on the potential role of immunotherapy, particularly programmed cell death protein 1/programmed cell death ligand 1 inhibitors, is rapidly expanding in both the early and metastatic settings with some preliminary evidence suggesting benefit when used as part of combination therapy. Several ongoing phase 3 studies should help define their future role in treating these patients.

Abstract Background Tucatinib is a highly selective HER2-directed tyrosine kinase inhibitor approved in combination with trastuzumab and capecitabine for previously treated HER2+ locally advanced or metastatic breast cancer (LA/MBC). Trastuzumab emtansine (T-DM1) is a HER2-directed antibody-drug conjugate approved to treat HER2+ LA/MBC previously treated with trastuzumab and a taxane. This is the first report of HER2CLIMB-02 (NCT03975647), a randomized, double-blind, placebo-controlled phase 3 study assessing the efficacy and safety of tucatinib combined with T-DM1 in patients with previously treated HER2+ LA/MBC. Methods Eligible patients had HER2+ LA/MBC previously treated with trastuzumab and a taxane in any setting with ECOG performance status ≤1 and adequate hepatic, renal, hematologic, and cardiac function. Patients with previously treated stable, progressing, or untreated brain metastases (BMs) not requiring immediate local therapy were also eligible. Patients were randomly assigned 1:1 to receive 21-day cycles of either tucatinib (300 mg orally twice a day [PO BID]) or placebo (PO BID), combined with T-DM1 (3.6 mg/kg intravenously every 3 weeks). The primary endpoint was progression-free survival (PFS) by investigator assessment per RECIST v1.1. Alpha-controlled secondary endpoints included overall survival (OS) and objective response rate (ORR) per RECIST v1.1 for the overall population, and PFS and OS for the subset of patients with BMs at baseline. Safety was analyzed as a secondary endpoint. Results From October 8, 2019, to June 16, 2022, 463 patients were randomly assigned, comprising 228 to the tucatinib arm (tucatinib + T-DM1) and 235 to the control arm (placebo + T-DM1). The median duration of follow-up (OS) was 24.4 months for the overall population. Patient demographics and baseline characteristics were balanced between the 2 arms. Almost half (44.1%) of the overall population had either active or stable BMs at baseline. As of the data cutoff (June 29, 2023), the study met its primary endpoint with a statistically significant improvement in PFS in the tucatinib arm vs control arm. The risk of progression or death decreased by 24.1% in the tucatinib arm (hazard ratio [HR]=0.759 [95% CI, 0.607-0.950]; P=0.0163). Median PFS was 9.5 months (95% CI, 7.4-10.9) vs 7.4 months (95% CI, 5.6-8.1) for the tucatinib and control arms, respectively. HRs for PFS across all prespecified subgroups were consistent with the HR of the overall population, including patients with BMs at baseline (HR=0.639 [95% CI, 0.459-0.891]). The interim OS results were immature with 134 of 253 total required events (53%) and did not meet the prespecified crossing boundary. The confirmed ORR was numerically higher in the tucatinib arm (42.0%) vs the control arm (36.1%). The most common treatment-emergent adverse events (TEAEs) included nausea (65.4% vs 49.4% for tucatinib and control arms, respectively), diarrhea (56.7% vs 26.6%), and fatigue (48.9% vs 37.3%). The most common grade ≥3 TEAEs in the tucatinib arm were alanine and aspartate aminotransferase elevations, each reported in 38 patients (16.5%) in the tucatinib arm and 6 patients (2.6%) in the control arm. TEAEs associated with any treatment discontinuation occurred in 51 patients (22.1%) in the tucatinib arm and 27 (11.6%) in the control arm. TEAEs leading to deaths occurred in 3 patients (1.3%) in the tucatinib arm and 2 patients (0.9%) in the control arm. Conclusion HER2CLIMB-02 demonstrated that the addition of tucatinib to T-DM1 significantly improved median PFS in patients with previously treated HER2+ LA/MBC, including those with BMs. Although discontinuations due to TEAEs were more common in the tucatinib arm, no new safety signals emerged for the combination therapy. Citation Format: Sara Hurvitz, Sherene Loi, Joyce O'Shaughnessy, Alicia Okines, Sara Tolaney, Joo Hyuk Sohn, Cristina Saura, Xiaofu Zhu, David Cameron, Thomas Bachelot, Erika Hamilton, Giuseppe Curigliano, Antonio Wolff, Nadia Harbeck, Norikazu Masuda, Linda Vahdat, Khalil Zaman, Frances Valdes-Albini, Margaret Block, Timothy Pluard, Tira Tan, Chelsea Gawryletz, Arlene Chan, Philippe Bedard, Rinat Yerushalmi, Binghe Xu, Konstantinos Tryfonidis, Michael Schmitt, Joan Xie, Virginia Borges. HER2CLIMB-02: Randomized, Double-Blind Phase 3 Trial of Tucatinib and Trastuzumab Emtansine for Previously Treated HER2-Positive Metastatic Breast Cancer [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr GS01-10.

Abstract Background: KEYNOTE-756 (NCT03725059) is a global phase 3 study of neoadjuvant pembrolizumab or placebo + chemotherapy followed by adjuvant pembrolizumab or placebo + endocrine therapy (ET) in patients with early-stage high-risk ER+/HER2– breast cancer. Here, we report primary pCR results and residual cancer burden (RCB) outcomes. Methods: Eligible patients with T1c-2 (≥2 cm) cN1-2 or T3-4 cN0-2, centrally confirmed, grade 3, invasive ductal ER+/HER2− breast cancer were randomized 1:1 to receive neoadjuvant pembrolizumab 200 mg Q3W or placebo, both given with paclitaxel QW for 12 weeks, then 4 cycles of doxorubicin or epirubicin + cyclophosphamide (neoadjuvant treatment). After definitive surgery (± radiation therapy), patients received pembrolizumab or placebo for 9 cycles + standard ET. Stratification factors include region (Eastern Europe, China, or Other), tumor PD-L1 status (CPS ≥1 [positive] vs CPS < 1 [negative]), nodal involvement (positive vs negative), ER positivity (≥10% vs < 10%) and anthracycline schedule (Q3W vs Q2W). Dual primary endpoints are pCR (ypT0/Tis ypN0) and EFS. Secondary endpoints include OS, pCR defined as ypT0 ypN0 and ypT0/Tis and safety. RCB was an exploratory endpoint and was assessed by a local pathologist at the time of surgery. RCB-0, -1, -2, and -3 denote increasingly larger residual disease. Results: 1278 patients were randomized to pembrolizumab + chemotherapy (n=635) or placebo + chemotherapy (n=643). At the final pCR analysis (May 25, 2023, first interim analysis data cutoff), median follow-up was 33.2 mo (range, 9.7-51.8). In the ITT population, pembrolizumab + chemotherapy showed a statistically significant improvement in pCR (ypT0/Tis ypN0) vs placebo + chemotherapy: 24.3% (95% CI, 21.0-27.8) vs 15.6% (95% CI, 12.8-18.6); estimated difference, 8.5 percentage points (95% CI, 4.2-12.8); P=0.00005; results were consistent for the secondary pCR definitions, ypT0 ypN0 (21.3% vs 12.8%) and ypT0/Tis (29.4% vs 18.2%). The benefit of pembrolizumab + chemotherapy on pCR was generally consistent in the prespecified subgroups. There were more patients with RCB-0 (24.7% vs. 15.6%) and RCB-1 (10.2% vs 8.1%) and fewer patients in the RCB-2 (40.8% vs. 45.3%) and RCB-3 categories (20.5% vs. 28.9%) in the pembrolizumab group versus the placebo group. In the neoadjuvant phase, grade ≥3 treatment-related AE rates were 52.5% with pembrolizumab + chemotherapy and 46.4% with placebo + chemotherapy, with 1 death in the pembrolizumab arm due to acute myocardial infarction. EFS results are still immature and continue to be evaluated. Conclusions: The addition of pembrolizumab to chemotherapy significantly increased the pCR rate and shifted RCB to lower residual disease categories in patients with early-stage high-risk ER+/HER2− breast cancer. Safety was consistent with the known profiles of each regimen. Citation Format: Fatima Cardoso, Joyce O'Shaughnessy, Heather McArthur, Peter Schmid, Javier Cortés, Nadia Harbeck, Melinda Telli, David Cescon, Peter A. Fasching, Zhimin Shao, Delphine Loirat, Yeon Hee Park, Manuel Gonzalez Fernandez, Gabor Rubovszky, Seock-Ah Im, Rina Hui, Toshimi Takano, Fabrice André, Hiroyuki Yasojima, Zhenzhen Liu, Yu Ding, Liyi Jia, Vassiliki Karantza, Konstantinos Tryfonidis, Aditya Bardia. Phase 3 study of neoadjuvant pembrolizumab or placebo plus chemotherapy, followed by adjuvant pembrolizumab or placebo plus endocrine therapy for early-stage high-risk ER+/HER2− breast cancer: KEYNOTE-756 [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr GS01-02.

Background: KEYNOTE-522 demonstrated statistically signi fi cant improvements in pathological complete response (pCR) with neoadjuvant pembrolizumab plus chemotherapy and event-free survival (EFS) with neoadjuvant pembrolizumab plus chemotherapy followed by adjuvant pembrolizumab in patients with high -risk, early-stage triple-negative breast cancer (TNBC). Prior studies have shown the prognostic value of the residual cancer burden (RCB) index to quantify the extent of residual disease after neoadjuvant chemotherapy. In this preplanned exploratory analysis, we assessed RCB distribution and EFS within RCB categories by treatment group. Patients and methods: A total of 1174 patients with stage T1c/N1-2 or T2 -4/N0-2 TNBC were randomized 2 : 1 to pembrolizumab 200 mg or placebo every 3 weeks given with four cycles of paclitaxel + carboplatin, followed by four cycles of doxorubicin or epirubicin + cyclophosphamide. After surgery, patients received pembrolizumab or placebo for nine cycles or until recurrence or unacceptable toxicity. Primary endpoints are pCR and EFS. RCB is a prespeci fi ed exploratory endpoint. The association between EFS and RCB was assessed using a Cox regression model. Results: Pembrolizumab shifted patients into lower RCB categories across the entire spectrum compared with placebo. There were more patients in the pembrolizumab group with RCB-0 (pCR), and fewer patients in the pembrolizumab group with RCB-1, RCB-2, and RCB-3. The corresponding hazard ratios (95% con fi dence intervals) for EFS were 0.70 (0.38-1.31), 0.92 (0.39-2.20), 0.52 (0.32-0.82), and 1.24 (0.69-2.23). The most common fi rst EFS events were distant recurrences, with fewer in the pembrolizumab group across all RCB categories. Among patients with RCB-0/1, more than half [21/38 (55.3%)] of all events were central nervous system recurrences, with 13/22 (59.1%) in the pembrolizumab group and 8/16 (50.0%) in the placebo group. Conclusions: Addition of pembrolizumab to chemotherapy resulted in fewer EFS events in the RCB-0, RCB-1, and RCB-2 categories, with the greatest bene fi t in RCB-2. These fi ndings demonstrate that pembrolizumab not only increased pCR rates, but also improved EFS among most patients who do not have a pCR.

Background: KEYNOTE-756 (NCT03725059) is a global phase 3 study of neoadjuvant pembrolizumab (pembro) or placebo (pbo) + chemotherapy (chemo) followed by adjuvant pembro or pbo + endocrine therapy (ET) in patients (pts) with early-stage high-risk ER+ /HER2– breast cancer. We report primary pCR results and residual cancer burden (RCB) outcomes.

BACKGROUND:KEYNOTE-522 demonstrated statistically significant improvements in pathological complete response (pCR) with neoadjuvant pembrolizumab plus chemotherapy and event-free survival (EFS) with neoadjuvant pembrolizumab plus chemotherapy followed by adjuvant pembrolizumab in patients with high-risk, early-stage triple-negative breast cancer (TNBC). Prior studies have shown the prognostic value of the residual cancer burden (RCB) index to quantify the extent of residual disease after neoadjuvant chemotherapy. In this preplanned exploratory analysis, we assessed RCB distribution and EFS within RCB categories by treatment group. PATIENTS AND METHODS:A total of 1174 patients with stage T1c/N1-2 or T2-4/N0-2 TNBC were randomized 2 : 1 to pembrolizumab 200 mg or placebo every 3 weeks given with four cycles of paclitaxel + carboplatin, followed by four cycles of doxorubicin or epirubicin + cyclophosphamide. After surgery, patients received pembrolizumab or placebo for nine cycles or until recurrence or unacceptable toxicity. Primary endpoints are pCR and EFS. RCB is a prespecified exploratory endpoint. The association between EFS and RCB was assessed using a Cox regression model. RESULTS:Pembrolizumab shifted patients into lower RCB categories across the entire spectrum compared with placebo. There were more patients in the pembrolizumab group with RCB-0 (pCR), and fewer patients in the pembrolizumab group with RCB-1, RCB-2, and RCB-3. The corresponding hazard ratios (95% confidence intervals) for EFS were 0.70 (0.38-1.31), 0.92 (0.39-2.20), 0.52 (0.32-0.82), and 1.24 (0.69-2.23). The most common first EFS events were distant recurrences, with fewer in the pembrolizumab group across all RCB categories. Among patients with RCB-0/1, more than half [21/38 (55.3%)] of all events were central nervous system recurrences, with 13/22 (59.1%) in the pembrolizumab group and 8/16 (50.0%) in the placebo group. CONCLUSIONS:Addition of pembrolizumab to chemotherapy resulted in fewer EFS events in the RCB-0, RCB-1, and RCB-2 categories, with the greatest benefit in RCB-2. These findings demonstrate that pembrolizumab not only increased pCR rates, but also improved EFS among most patients who do not have a pCR.

Abstract Background The current first-line (1L) standard of care (SOC) for human epidermal growth factor receptor 2-positive (HER2+) metastatic breast cancer (MBC) is trastuzumab (T) plus pertuzumab (P) and a taxane. Despite advances in 1L SOC, most patients progress during maintenance therapy with T+P. Tucatinib is a tyrosine kinase inhibitor (TKI) approved in combination with T and capecitabine for adults with HER2+ MBC, with and without brain metastases (BM). In HER2CLIMB, addition of tucatinib significantly prolonged progression-free survival (PFS) and overall survival (OS) in patients with HER2+ MBC and was well tolerated. Adding tucatinib also reduced the risk of disease progression or death in patients with untreated and/or active BM (Murthy et al. NEJM 2020, Curigliano et al. Ann Oncol 2022). HER2CLIMB-05 investigates whether adding tucatinib to 1L SOC as maintenance therapy will extend PFS while maintaining quality of life (QOL). Methods HER2CLIMB-05 (NCT05132582) is a phase 3, randomized, double-blind study evaluating tucatinib plus T+P as maintenance therapy for HER2+ MBC. Approximately 650 patients will be enrolled. Eligible patients will have advanced HER2+ disease, no progression on 4–8 cycles of prior 1L SOC, Eastern Cooperative Oncology Group Performance Status of 0 or 1, and no or asymptomatic BM. Exclusion criteria include prior treatment with anti-HER2 and/or anti-epidermal growth factor receptor TKI (prior SOC for early BC is permitted) or inability to undergo contrast magnetic resonance imaging of the brain. Patients will be randomized 1:1 to receive either tucatinib or placebo twice daily, with T+P once every 21 days. Patients with hormone receptor-positive disease may receive endocrine therapy. The primary endpoint is investigator-assessed PFS. Secondary endpoints include OS, time to deterioration of health-related QOL, central nervous system PFS, safety, and pharmacokinetic (PK) parameters. PFS and OS will be compared using a two-sided stratified log-rank test between treatment groups. Time-to-event endpoints will be summarized using the Kaplan–Meier method. PK and safety data will be summarized using descriptive statistics. Enrollment is ongoing in Austria, Chile, Greece, Italy, Japan, Poland, Portugal, Spain, the US, and several other European, APAC, and LATAM countries. This abstract was previously presented at ESMO-BC 2022, FPN (Final Publication Number): 415, by Veronique Dieras (reused with permission). Citation Format: Erika Hamilton, Junji Tsurutani, Giuseppe Curigliano, Miguel Martín, Ciara O'Sullivan, Joo Hyuk Sohn, Konstantinos Tryfonidis, Libero Santarpia, Shan Yang, Véronique Diéras. Phase 3 Study of Tucatinib or Placebo in Combination With Trastuzumab and Pertuzumab as Maintenance Therapy for HER2+ Metastatic Breast Cancer (HER2CLIMB-05, Trial in Progress) [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO1-19-11.

Abstract Background: In KEYNOTE-522 (NCT03036488), neoadjuvant pembrolizumab (pembro) plus chemotherapy (chemo) followed by adjuvant pembro showed statistically significant and clinically meaningful improvements in pathological complete response (pCR) and event-free survival (EFS) compared with neoadjuvant placebo (pbo) plus chemo followed by adjuvant pbo in patients (pts) with early-stage triple-negative breast cancer (TNBC). Here, we present updated EFS results after a median follow-up of ~5 y. Methods: Eligible pts with previously untreated, non-metastatic, centrally confirmed TNBC (stage T1c N1-2 or T2-4 N0-2 per American Joint Committee on Cancer) were randomized 2:1 to neoadjuvant pembro 200 mg Q3W or placebo (pbo), both given with 4 cycles of paclitaxel + carboplatin, then with 4 cycles of doxorubicin or epirubicin + cyclophosphamide. After definitive surgery, pts received adjuvant pembro or pbo for 9 cycles or until recurrence or unacceptable toxicity. Dual primary endpoints are pCR (ypT0/Tis ypN0) and EFS (time from randomization to disease progression that precluded definitive surgery, local/distant recurrence, second primary cancer, or death from any cause). Results: 1174 pts were randomized to pembro (n=784) or pbo (n=390) group. At data cutoff (March 23, 2023), median follow-up was 63.1 mo. 145 pts (18.5%) in the pembro group and 108 pts (27.7%) in the pbo group had an EFS event (hazard ratio [HR] 0.63 [95% CI, 0.49-0.81]). The 60-mo EFS rate (95% CI) was 81.3% (78.4-83.9) vs 72.3% (67.5-76.5), respectively; the median was not reached in either group. The benefit of neoadjuvant pembro + chemo followed by adjuvant pembro versus neoadjuvant chemo alone was consistent with the primary EFS results in all 5 sensitivity analyses, showing durable and robust EFS benefit in the pembro arm. The EFS benefit with pembro was consistent across prespecified subgroups, including PD-L1 expression, nodal status, disease stage, menopausal status, HER2 status, and lactate dehydrogenase (LDH) level (table). In a prespecified, non-randomized, exploratory analysis, 5-yr EFS rates in the pembro and pbo groups were 92.2% vs 88.2% in pts with a pCR, and 62.6% vs 52.3% in pts without a pCR. Additional analyses will be included in the presentation. Follow-up for OS is ongoing Conclusions: Neoadjuvant pembro + chemo followed by adjuvant pembro continues to show a clinically meaningful improvement in EFS compared with neoadjuvant chemo alone in pts with early-stage TNBC. This is seen across subgroups and regardless of the pCR outcome. Table. EFS results in overall population and by subgroup Citation Format: Peter Schmid, Javier Cortés, Rebecca Dent, Lajos Pusztai, Heather McArthur, Sherko Küemmel, Carsten Denkert, Yeon Hee Park, Rina Hui, Nadia Harbeck, Masato Takahashi, Theodoros Foukakis, Marie-Ange Mouret-Reynier, Marta Ferreira, Seock-Ah Im, Fatima Cardoso, Yu Ding, Wilbur Pan, Konstantinos Tryfonidis, Joyce O'Shaughnessy. Neoadjuvant pembrolizumab or placebo plus chemotherapy followed by adjuvant pembrolizumab or placebo for early-stage triple-negative breast cancer: Updated event-free survival results from the phase 3 KEYNOTE-522 study [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr LBO1-01.

TPS1115 Background: The current first-line (1L) standard of care (SOC) for human epidermal growth factor receptor 2-positive (HER2+) metastatic breast cancer (MBC) is trastuzumab (T) plus pertuzumab (P) and a taxane. Despite advances in 1L SOC, most patients progress during maintenance therapy with T + P. Tucatinib is a tyrosine kinase inhibitor (TKI) approved in combination with T and capecitabine for adults with HER2+ MBC, with and without brain metastases (BM). In HER2CLIMB, the addition of tucatinib significantly prolonged progression-free survival (PFS) and overall survival (OS) in patients with HER2+ MBC and was well tolerated. Adding tucatinib also reduced the risk of disease progression or death in patients with untreated and/or active BM (Murthy et al. 2020, Curigliano et al. 2021). HER2CLIMB-05 investigates whether adding tucatinib to 1L SOC as maintenance therapy will extend PFS while maintaining quality of life (QOL). Methods: HER2CLIMB-05 (NCT05132582) is a phase 3, randomized, double-blind study evaluating tucatinib plus T + P as maintenance therapy for HER2+ MBC. Approximately 650 patients will be enrolled. Eligible patients will have advanced HER2+ disease, no progression on 4–8 cycles of prior 1L SOC, Eastern Cooperative Oncology Group Performance Status of 0 or 1, and no or asymptomatic BM. Exclusion criteria include prior treatment with anti-HER2 and/or anti-epidermal growth factor receptor TKI (prior SOC for early BC is permitted) or inability to undergo contrast magnetic resonance imaging of the brain. Patients will be randomized 1:1 to receive either tucatinib or placebo twice daily, with T + P once every 21 days. Patients with hormone receptor-positive disease may receive endocrine therapy. The primary endpoint is investigator-assessed PFS. Secondary endpoints include OS (key endpoint), PFS by Blinded Independent Central Review (BICR), time to deterioration of health-related QOL, central nervous system PFS, safety, and pharmacokinetic (PK) parameters. PFS and OS will be compared using a 2-sided stratified log-rank test between treatment groups. Time-to-event endpoints will be summarized using the Kaplan–Meier method. PK and safety data will be summarized using descriptive statistics. Enrollment is ongoing in the US, Canada, Brazil, APAC and EU countries with additional sites planned. Clinical trial information: NCT05132582 .

Abstract Background: The current first-line (1L) standard of care (SOC) for human epidermal growth factor receptor 2-positive (HER2+) metastatic breast cancer (MBC) is trastuzumab (T) plus pertuzumab (P) and a taxane. Despite advances in 1L SOC, most patients (pts) progress during maintenance therapy with T+P. Tucatinib is a tyrosine kinase inhibitor (TKI) approved in combination with T and capecitabine for adults with HER2+ MBC, with and without brain metastases (BM). In HER2CLIMB, the addition of tucatinib significantly prolonged progression-free survival (PFS) and overall survival (OS) in pts with HER2+ MBC and was well tolerated. Adding tucatinib also reduced the risk of disease progression or death in pts with untreated and/or active BM (Murthy et al. 2020, Curigliano et al. 2021). HER2CLIMB-05 investigates whether adding tucatinib to 1L SOC as maintenance therapy will extend PFS while maintaining quality of life (QOL). Methods: HER2CLIMB-05 (NCT05132582) is a phase 3, randomized, double-blind study evaluating tucatinib plus T+P as maintenance therapy for HER2+ MBC. Approximately 650 pts will be enrolled. Eligible pts will have advanced HER2+ disease, no progression on 4–8 cycles of prior 1L SOC, ECOG Performance Status of 0 or 1, and no or asymptomatic BM. Exclusion criteria include prior treatment with anti-HER2 and/or anti-epidermal growth factor receptor TKI (prior SOC for early BC is permitted) or inability to undergo contrast magnetic resonance imaging of the brain. Pts will be randomized 1:1 to receive either tucatinib or placebo twice daily, with T+P once every 21 days. Pts with HR+ disease may receive endocrine therapy. The primary endpoint is investigator-assessed PFS. Secondary endpoints include OS (key endpoint), time to deterioration of health-related QOL, central nervous system PFS, safety, and pharmacokinetic (PK) parameters. PFS and OS will be compared using a 2-sided stratified log-rank test between treatment groups. Time-to-event endpoints will be summarized using the Kaplan–Meier method. PK and safety data will be summarized using descriptive statistics. Enrollment is ongoing in the US, with additional sites planned. Citation Format: Erika Hamilton, Junji Tsurutani, Giuseppe Curigliano, Miguel Martín, Ciara C. O’Sullivan, Joo Hyuk Sohn, Konstantinos Tryfonidis, Libero Santarpia, Shan Yang, Véronique Diéras. Phase 3 study of tucatinib or placebo in combination with trastuzumab and pertuzumab as maintenance therapy for HER2+ metastatic breast cancer (HER2CLIMB-05, trial in progress) [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr OT2-16-03.

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

local assessments of progression free survival

Background A high-risk subpopulation of ER+/HER2− breast cancer (BC) is characterized by high-grade tumors, decreased sensitivity to endocrine therapy (ET), higher responsiveness to chemotherapy (CT), and worse prognosis. Prior studies suggest that increased pathological complete response (pCR) rates after neoadjuvant CT may have a substantial impact for patients with high-risk, early-stage, HR+/HER2− BC. KEYNOTE-756 (NCT03725059) is a global, randomized, double-blind, phase 3 study of pembrolizumab (vs placebo) + CT as neoadjuvant treatment followed by pembrolizumab (vs placebo) + ET as adjuvant treatment for patients with high-risk, early-stage, ER+/HER2− BC. Trial design Patients with T1c-2 cN1-2 (tumor size ≥2 cm) or T3-4 cN0-2 grade 3, invasive, ductal ER+/HER2− BC will be stratified by lymph node involvement (positive vs negative), tumor PD-L1 status (positive [CPS ≥1] vs negative [CPS Clinical trial identification NCT03725059. Legal entity responsible for the study Merck & Co., Inc. Funding Funding for this study was provided by Merck Sharp & Dohme Corp., a subsidiary of Merck & Co., Inc., Kenilworth, NJ, USA. Disclosure F. Cardoso: Advisory / Consultancy: Amgen; Advisory / Consultancy: Astellas/Medivation; Advisory / Consultancy: AstraZeneca; Advisory / Consultancy: Celgene; Advisory / Consultancy: Daiichi-Sankyo; Advisory / Consultancy: Eisai; Advisory / Consultancy: GE Oncology; Advisory / Consultancy: Genentech; Advisory / Consultancy: GlaxoSmithKline; Advisory / Consultancy: Macrogenics; Advisory / Consultancy: Medscape; Advisory / Consultancy: Merck-Sharp; Advisory / Consultancy: Merus BV; Advisory / Consultancy: Mylan; Advisory / Consultancy: Mundipharma GmbH; Advisory / Consultancy: Novartis; Advisory / Consultancy: Pfizer; Advisory / Consultancy: Pierre-Fabre; Advisory / Consultancy: prIME Oncology; Advisory / Consultancy: Roche. A. Bardia: Advisory / Consultancy, Research grant / Funding (self): bioTheranostics; Advisory / Consultancy: Genentech; Advisory / Consultancy: Genentech/Roche; Advisory / Consultancy: Immunomedics; Advisory / Consultancy: Innocrin Pharmaceuticals; Advisory / Consultancy: Merck; Advisory / Consultancy: Novartis; Advisory / Consultancy: Pfizer; Advisory / Consultancy: Radius Health; Advisory / Consultancy: Radius Pharma; Advisory / Consultancy: Sanofi; Advisory / Consultancy: Spectrum Pharmaceuticals. F. Andre: Research grant / Funding (institution): Novartis; Research grant / Funding (institution): AstraZeneca; Research grant / Funding (institution): Pfizer; Research grant / Funding (institution): Lilly; Research grant / Funding (institution): Roche. D.W. Cescon: Honoraria (self), Advisory / Consultancy: Novartis; Honoraria (self), Advisory / Consultancy: Pfizer; Advisory / Consultancy: AstraZeneca; Advisory / Consultancy: Genomic Health; Advisory / Consultancy, Research grant / Funding (institution): GlaxoSmithKline; Advisory / Consultancy, Research grant / Funding (institution): Merck; Research grant / Funding (institution): Roche/Genentech. H. McArthur: Advisory / Consultancy: Celgene; Advisory / Consultancy, Research grant / Funding (self): Merck; Advisory / Consultancy: OBI Pharma; Advisory / Consultancy: Roche; Advisory / Consultancy: Spectrum Pharmaceuticals; Advisory / Consultancy: Syndax Pharmaceuticals; Advisory / Consultancy: Peregrine; Advisory / Consultancy: Calithera; Research grant / Funding (self): Bristol-Myers Squibb; Research grant / Funding (self): Eli Lilly; Research grant / Funding (self): MedImmunne; Research grant / Funding (self): LLC/AstraZeneca. M. Telli: Advisory / Consultancy, Research grant / Funding (institution): Merck; Advisory / Consultancy, Research grant / Funding (institution): Genentech; Advisory / Consultancy: Aduro; Advisory / Consultancy, Research grant / Funding (institution): Pfizer; Advisory / Consultancy: Immunomedics; Advisory / Consultancy: Celldex; Advisory / Consultancy, Research grant / Funding (institution): Tesaro; Research grant / Funding (institution): OncoSec; Research grant / Funding (institution): Biothera; Research grant / Funding (institution): Vertex; Research grant / Funding (institution): Calithera; Research grant / Funding (institution): Merck Serono; Research grant / Funding (institution): PharmaMar. S. Loi: Advisory / Consultancy: AstraZeneca/MedImmune; Advisory / Consultancy, Research grant / Funding (institution): Bristol-Myers Squibb; Advisory / Consultancy, Research grant / Funding (institution): Merck; Advisory / Consultancy: Pfizer; Advisory / Consultancy, Research grant / Funding (institution): Roche/Genentech; Advisory / Consultancy: Seattle Genetics; Research grant / Funding (institution): Lilly; Research grant / Funding (institution): Novartis; Research grant / Funding (institution): Puma Biotechnology. J. Cortes: Shareholder / Stockholder / Stock options: MedSIR; Honoraria (self), Travel / Accommodation / Expenses: Novartis; Honoraria (self), Research grant / Funding (institution), Travel / Accommodation / Expenses: Eisai; Honoraria (self), Advisory / Consultancy: Celgene; Honoraria (self), Research grant / Funding (institution), Travel / Accommodation / Expenses: Pfizer; Honoraria (self), Advisory / Consultancy, Travel / Accommodation / Expenses: Roche; Honoraria (self): Samsung; Advisory / Consultancy: Cellestia Biotech; Advisory / Consultancy, Research grant / Funding (institution): AstaZeneca; Advisory / Consultancy: Biothera; Advisory / Consultancy: Merus; Advisory / Consultancy: Seattle Genetics; Advisory / Consultancy: Daiichi-Sankyo; Advisory / Consultancy: ERYTECH Pharma; Advisory / Consultancy: Polyphor; Research grant / Funding (institution): ARIAD; Research grant / Funding (institution): Baxalta GmbH; Research grant / Funding (institution): Bayer; Research grant / Funding (institution): Guardant Health; Research grant / Funding (institution): Merck. P. Schmid: Full / Part-time employment: Roche; Honoraria (self), Research grant / Funding (institution): AstraZeneca; Honoraria (self): Bayer; Honoraria (self): Boehringer Ingelheim; Honoraria (self): Celgene; Honoraria (self): Eisai; Honoraria (self), Research grant / Funding (institution): Genentech/Roche; Honoraria (self), Research grant / Funding (institution): Merck; Honoraria (self), Research grant / Funding (institution): Novartis; Honoraria (self): Pfizer; Honoraria (self): Puma Biotechnology; Research grant / Funding (institution): Astellas Pharma; Research grant / Funding (institution): Medivation; Research grant / Funding (institution): Oncogenex. N. Harbeck: Honoraria (self), Advisory / Consultancy: Lilly; Honoraria (self), Advisory / Consultancy: Novartis; Honoraria (self), Advisory / Consultancy: Pfizer. C. Denkert: Honoraria (self), Advisory / Consultancy: Amgen; Honoraria (self): Novartis; Honoraria (self): Pfizer; Honoraria (self): Teva; Honoraria (self): Roche; Shareholder / Stockholder / Stock options: Sividon Diagnostics; Advisory / Consultancy: Daiichi-Sankyo; Advisory / Consultancy: MSD Oncology; Licensing / Royalties, patent application—therapy response: EP20150702464; Licensing / Royalties, patent application— cancer immunotherapy: EP18209672; Licensing / Royalties, digital pathology software: VMScope. C. Jackisch: Honoraria (self), Advisory / Consultancy: Merck. L. Jia: Travel / Accommodation / Expenses, Shareholder / Stockholder / Stock options, Full / Part-time employment: Merck. K. Hirshfield: Shareholder / Stockholder / Stock options, Full / Part-time employment: Merck. V. Karantza: Shareholder / Stockholder / Stock options, Full / Part-time employment: Merck.