• Javier Cortes, Hope S Rugo, David W Cescon, Seock-Ah Im, Mastura M Yusof, Carlos Gallardo, Oleg Lipatov, Carlos H Barrios, Jose Perez-Garcia, Hiroji Iwata, Norikazu Masuda, Torregroza OteroMarcoMFrom the International Breast Cancer Center, Pangaea Oncology, Quirónsalud Group, Barcelona (J.C., J.P.-G.), and the Faculty of Biomedical and Health Sciences, Department of Medicine, Universidad Europea de Madrid, Madrid (J.C.) - bo, Erhan Gokmen, Sherene Loi, Zifang Guo, Xuan Zhou, Vassiliki Karantza, Wilbur Pan, Peter Schmid, and KEYNOTE-355 Investigators.
• From the International Breast Cancer Center, Pangaea Oncology, Quirónsalud Group, Barcelona (J.C., J.P.-G.), and the Faculty of Biomedical and Health Sciences, Department of Medicine, Universidad Europea de Madrid, Madrid (J.C.) - both in Spain; the Department of Medicine, University of California San Francisco Comprehensive Cancer Center, San Francisco (H.S.R.); Princess Margaret Cancer Centre, Toronto (D.W.C.); Seoul National University Hospital, Cancer Research Institute, Seoul National University College of Medicine, Seoul (S.-A.I.); Cancer Center at Pantai Hospital Kuala Lumpur, Kuala Lumpur, Malaysia (M.M.Y.); the Oncology Institute, Arturo Lopez Perez Foundation, Santiago, Chile (C.G.); the Department of Oncology, Republican Clinical Oncology Dispensary, Ufa, Russia (O.L.); the Oncology Research Unit, Hospital São Lucas, Pontifical Catholic University of Rio Grande do Sul, Porto Alegre, Brazil (C.H.B.); the Department of Breast Oncology, Aichi Cancer Center Hospital (H.I.), and the Department of Breast and Endocrine Surgery, Nagoya University Graduate School of Medicine (N.M.) - both in Nagoya, Japan; the Department of Hematology and Oncology, Oncomedica, Montería, Colombia (M.T.O.); Ege University Medical Faculty, Izmir, Turkey (E.G.); the Division of Cancer Research, Peter MacCallum Cancer Centre, Melbourne, and the Sir Peter MacCallum Department of Oncology, University of Melbourne, Parkville - both in Australia (S.L.); Merck, Rahway, NJ (Z.G., X.Z., V.K., W.P.); and the Centre for Experimental Cancer Medicine, Barts Cancer Institute, Queen Mary University of London, London (P.S.).
• N. Engl. J. Med. 2022 Jul 21; 387 (3): 217-226.

BackgroundIn an interim analysis of this phase 3 trial, the addition of pembrolizumab to chemotherapy resulted in longer progression-free survival than chemotherapy alone among patients with advanced triple-negative breast cancer whose tumors expressed programmed death ligand 1 (PD-L1) with a combined positive score (CPS; the number of PD-L1-staining tumor cells, lymphocytes, and macrophages, divided by the total number of viable tumor cells, multiplied by 100) of 10 or more. The results of the final analysis of overall survival have not been reported.MethodsWe randomly assigned patients with previously untreated locally recurrent inoperable or metastatic triple-negative breast cancer in a 2:1 ratio to receive pembrolizumab (200 mg) every 3 weeks plus the investigator's choice of chemotherapy (nanoparticle albumin-bound paclitaxel, paclitaxel, or gemcitabine-carboplatin) or placebo plus chemotherapy. The primary end points were progression-free survival (reported previously) and overall survival among patients whose tumors expressed PD-L1 with a CPS of 10 or more (the CPS-10 subgroup), among patients whose tumors expressed PD-L1 with a CPS of 1 or more (the CPS-1 subgroup), and in the intention-to-treat population. Safety was also assessed.ResultsA total of 847 patients underwent randomization: 566 were assigned to the pembrolizumab-chemotherapy group, and 281 to the placebo-chemotherapy group. The median follow-up was 44.1 months. In the CPS-10 subgroup, the median overall survival was 23.0 months in the pembrolizumab-chemotherapy group and 16.1 months in the placebo-chemotherapy group (hazard ratio for death, 0.73; 95% confidence interval [CI], 0.55 to 0.95; two-sided P = 0.0185 [criterion for significance met]); in the CPS-1 subgroup, the median overall survival was 17.6 and 16.0 months in the two groups, respectively (hazard ratio, 0.86; 95% CI, 0.72 to 1.04; two-sided P = 0.1125 [not significant]); and in the intention-to-treat population, the median overall survival was 17.2 and 15.5 months, respectively (hazard ratio, 0.89; 95% CI, 0.76 to 1.05 [significance not tested]). Adverse events of grade 3, 4, or 5 that were related to the trial regimen occurred in 68.1% of the patients in the pembrolizumab-chemotherapy group and in 66.9% in the placebo-chemotherapy group, including death in 0.4% of the patients in the pembrolizumab-chemotherapy group and in no patients in the placebo-chemotherapy group.ConclusionsAmong patients with advanced triple-negative breast cancer whose tumors expressed PD-L1 with a CPS of 10 or more, the addition of pembrolizumab to chemotherapy resulted in significantly longer overall survival than chemotherapy alone. (Funded by Merck Sharp and Dohme; KEYNOTE-355 ClinicalTrials.gov number, NCT02819518.).Copyright © 2022 Massachusetts Medical Society.

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