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William J. Gradishar, MD, FACP, FASCO
William J. Gradishar, MD, FACP, FASCO
Posted: Tuesday, December 12, 2023
Fatima Cardoso, MD, of Champalimaud Clinical Center, Lisbon, and colleagues recently reported pathologic complete response–quantified and residual cancer burden (RCB) data for KEYNOTE-756. This phase III trial evaluated neoadjuvant pembrolizumab or placebo plus chemotherapy, followed by adjuvant pembrolizumab or placebo plus endocrine therapy, for early-stage, high-risk, estrogen receptor (ER)-positive, HER2-negative breast cancer.
Presented at the 2023 San Antonio Breast Cancer Symposium (SABCS; Abstract GS01-02), their data demonstrated that the addition of neoadjuvant pembrolizumab to chemotherapy significantly increased the measured pathologic complete response rate and shifted RCB (a pathologist-designated exploratory endpoint) toward lower residual disease in assessed patients.
A total of 1,278 patients were randomly assigned to receive pembrolizumab plus chemotherapy (n = 635) or placebo plus chemotherapy (n = 643). They all had T1c–2 (≥ 2 cm) cN1–2 or T3–4 cN0–2, centrally confirmed, grade 3, invasive ductal ER-positive, HER2-negative breast cancer.
At the final pathologic complete response analysis, the median follow-up was 33.2 months (range, 9.7–51.8 months). In the intention-to-treat population, pembrolizumab plus chemotherapy yielded a statistically significant improvement in the primary pathologic complete response–defined outcome (ypT0/Tis ypN0) compared with placebo plus chemotherapy; the respective rates were 24.3% (95% confidence interval [CI] = 21.0%–27.8%) and 15.6% (95% CI = 12.8%–18.6%; P = .00005). Results were consistent for the secondary pathologic complete response–defined outcomes: ypT0 ypN0 (21.3% vs 12.8%) and ypT0/Tis (29.4% vs 18.2%), respectively. More patients were found to have lower residual cancer burdens (RCB-0/RCB-1) than higher residual burdens (RCB-2/RCB-3).
The rates of treatment-related adverse events were 52.5% with pembrolizumab plus chemotherapy and 46.4% with placebo plus chemotherapy. One death (from acute myocardial infarction) occurred in the pembrolizumab arm.
Disclosure: For full disclosures of study authors, visit atgproductions.net.
2023 San Antonio Breast Cancer Symposium
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