Breast Cancer Coverage from Every Angle

KEYNOTE-119: Pembrolizumab Versus Chemotherapy in Triple-Negative Breast Cancer

By: Noelle Cutter, PhD
Posted: Monday, May 3, 2021

Based on the phase III KEYNOTE-119 trial, published in The Lancet Oncology, pembrolizumab monotherapy versus single-drug chemotherapy for patients with previously treated metastatic triple-negative breast cancer did not significantly improve overall survival. However, patients with PD-L1–enriched tumors experienced longer progression-free survival with the anti–PD-1 inhibitor.

“These finding suggest that patients with PD-L1–positive, triple-negative breast cancer have an increased likelihood of clinical response to immune checkpoint inhibitors,” noted Eric P. Winer, MD, of Dana-Farber Cancer Institute, Boston, and colleagues. “These findings might inform future research of pembrolizumab monotherapy for selected subpopulations of patients…and inform a combinatorial approach for the treatment of patients with metastatic triple-negative breast cancer.”

The 31-month study included 150 medical centers in 31 countries. A total of 622 patients with confirmed metastatic triple-negative breast cancer were randomly assigned to receive either 200 mg of pembrolizumab intravenously every 3 weeks or the investigator’s choice of chemotherapy. PD-L1 expression was determined using a PD-L1 immunohistochemical assay. 

The median survival with pembrolizumab was 9.9 months versus10.8 months with chemotherapy (hazard ratio = 0.97 [95% confidence interval [CI] = 0.82–1.15]) in the overall population. In patients with a PD-L1 combined positive score (CPS) of 10 or more, the median overall survival was 12.7 months with pembrolizumab and 11.6 months with chemotherapy (HR = 0.78 [95% CI = 0.57–1.06] log-rank P = .057). The median overall survival for participants with a PD-L1 CPS of 1 or more was 10.7 months with pembrolizumab and 10.2 months with chemotherapy (HR = 0.97 [95% CI = 0.69–1.06]; log-rank P = .073).

Grade 3 or 4 treatment-related adverse events were seen in 43 of 309 patients (14%) in the pembrolizumab group and 105 of 292 patients (36%) in the chemotherapy group. Serious adverse events were seen in 20% of both patient groups. Of the 601 participants, 3 were reported to have had treatment-related adverse events that led to death. 

Disclosure: For full disclosures of the study authors, visit

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