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Dr Heather McArthur Speaks on the KEYNOTE-522 Trial

Dr Heather McArthur Speaks on the KEYNOTE-522 Trial

Pembrolizumab Meets Dual Endpoints in KEYNOTE-522 Trial for Triple-Negative Breast Cancer


Pembrolizumab met its dual endpoints of event-free survival (EFS) and pathological complete response (pCR) at the interim analysis of the phase 3 KEYNOTE-522 trial, which explored the anti–PD-1 therapy’s efficacy in high-risk, early-stage, triple-negative breast cancer (TNBC).

In the KEYNOTE-522 trial, 1174 patients were randomized 2:1 to receive paclitaxel and carboplatin plus either pembrolizumab or placebo for 4 cycles, followed by cyclophosphamide and doxorubin or epirubicin plus either pembrolizumab or placebo for 4 cycles as neoadjuvant therapy before surgery. Following surgery, patients received 9 cycles of either pembrolizumab or placebo post-surgery. There were 784 patients in the pembrolizumab cohort and 390 in the placebo cohort.

According to the interim analysis, the pembrolizumab arm showed a statistically significant and clinically meaningful improvement in EFS when compared to the placebo arm. No new safety signals for pembrolizumab were identified in this trial.

“To assess the robustness and consistency of the primary EFS result… [f]ive prespecified sensitivity analyses for EFS were performed, including 2 that assessed the impact of different censoring rules and 3 that assessed the impact of different event definitions,” wrote Peter Schmid, MD, PhD, Barts Cancer Institute, Queen Mary University London, lead author of the abstract discussing KEYNOTE-522 presented at the 2021 SABC Symposium.

The study authors concluded, “The benefit of neoadjuvant pembro + chemo followed by adjuvant pembro vs neoadjuvant chemo alone was generally consistent with the primary EFS results for all five sensitivity analyses and in each subgroup evaluated.”



Merck announces phase 3 KEYNOTE-522 trial met dual primary endpoint of event-free survival (EFS) in patients with high-risk early-sStage triple-negative breast cancer (TNBC). News release. Merck. May 13, 2021. Accessed March 12, 2022.

Schmid P, Cortes J, Dent R, et al. KEYNOTE-522 study of neoadjuvant pembrolizumab + chemotherapy vs placebo + chemotherapy, followed by adjuvant pembrolizumab vs placebo for early-stage TNBC: Event-free survival sensitivity and subgroup analyses. Abstract