HealthDay News — The addition of pembrolizumab to chemotherapy is associated with significantly longer overall survival than chemotherapy alone among patients with advanced triple-negative breast cancer whose tumors express programmed death ligand 1 (PD-L1) with a combined positive score (CPS) of 10 or more (CPS-10 subgroup), according to a study published in the July 21 issue of the New England Journal of Medicine.

Javier Cortes, MD, PhD, from the International Breast Cancer Center in Barcelona, Spain, and colleagues randomly assigned patients with previously untreated locally recurrent inoperable or metastatic triple-negative breast cancer to receive pembrolizumab every 3 weeks plus the investigator’s choice of chemotherapy or placebo plus chemotherapy (566 and 281 patients, respectively). Primary end points included overall survival among the CPS-10 subgroup and among the CPS-1 subgroup. Patients were followed for a median of 44.1 months.

The researchers found that the median overall survival was 23.0 and 16.1 months in the pembrolizumab-chemotherapy and placebo-chemotherapy groups, respectively, in the CPS-10 subgroup (hazard ratio for death, 0.73; 95% CI, 0.55 to 0.95; two-sided P =.0185 [criterion for significance met]). The median overall survival was 17.6 and 16.0 months, respectively, in the CPS-1 subgroup (hazard ratio, 0.86; 95% CI, 0.72 to 1.04; two-sided P =.1125 [not significant]). Adverse events of grade 3, 4, or 5 that were related to the trial regimen occurred in 68.1 and 66.9% of patients, respectively.

“These results confirm the relationship between [PD-L1] expression and the activity of pembrolizumab in preclinical and clinical studies,” writes the author of an accompanying editorial.

The study was funded by Merck Sharp and Dohme, the manufacturer of pembrolizumab.

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