Multinational phase 3 trial of neoadjuvant pembrolizumab plus chemotherapy, followed by adjuvant pembrolizumab plus endocrine therapy for high-risk ER+/HER2- breast cancer

The multinational phase 3 KEYNOTE-756 trial randomized patients with early-stage high-risk ER-positive/HER2-negative breast cancer to neoadjuvant pembrolizumab plus chemotherapy (n=635) or placebo plus chemotherapy (n=643) followed by surgery and pembrolizumab plus endocrine therapy or placebo plus endocrine therapy. Coprimary endpoints are pathologic complete response (pCR) and event-free survival (EFS). First interim analysis results (median follow-up 33.2 months; range 7.9-51.8) have now been presented. Addition of pembrolizumab to neoadjuvant chemotherapy significantly increased the pCR rate and shifted residual cancer burden to lower residual disease categories. Safety was consistent with the known profiles of each regimen. EFS results are immature and continue to be evaluated.