Pembrolizumab in the preoperative setting of triple-negative breast cancer: safety and efficacy.

INTRODUCTION: In 2019, the PD-L1 inhibitor atezolizumab became the first immune checkpoint inhibitor approved for treatment in patients with breast cancer. The approval is restricted to patients with metastatic triple-negative breast cancer (TNBC) whose tumors are PD-L1 positive. There is a rationale to believe that using PD-1/L1 inhibitors in the early disease setting may be associated with even greater benefit than seen in the metastatic setting.

AREAS COVERED: We review the results of pembrolizumab studies in the metastatic setting as well as the rationale for using immunotherapy in the preoperative setting. We also present current data pembrolizumab in the treatment of breast cancer with focus on the early-stage setting and discuss areas of uncertainty.

EXPERT OPINION: The KEYNOTE-552 study showed, for the first time, that the addition of pembrolizumab to preoperative chemotherapy increases pathologic complete response rates. Event-free survival data are promising and longer follow-up is needed to determine whether the addition of pembrolizumab significantly improves long-term outcomes for patients with early-stage TNBC.