Pembrolizumab in Patients With Advanced Triple-Negative Breast Cancer: Phase Ib KEYNOTE-012 Study

PurposeImmune checkpoint inhibition has been demonstrated to be an effective anticancer strategy. Several lines of evidence support the study of immunotherapy in triple-negative breast cancer (TNBC). We assessed the safety and antitumor activity of the programmed cell death protein 1 (PD-1) inhibitor pembrolizumab in patients with advanced TNBC.MethodsKEYNOTE-012 (ClinicalTrials.gov identifier: NCT01848834) was a multicenter, nonrandomized phase Ib trial of single-agent pembrolizumab given intravenously at 10 mg/kg every 2 weeks to patients with advanced PD-L1–positive (expression in stroma or ≥ 1% of tumor cells by immunohistochemistry) TNBC, gastric cancer, urothelial cancer, and head and neck cancer. This report focuses on the TNBC cohort.ResultsAmong 111 patients with TNBC whose tumor samples were screened for PD-L1 expression, 58.6% had PD-L1–positive tumors. Thirty-two women (median age, 50.5 years; range, 29 to 72 years) were enrolled and assessed for safety and antitumor activity. The median numbe...