The evolving role of immune checkpoint inhibitors in the treatment of triple-negative breast cancer.

Triple-negative breast cancer (TNBC) is an aggressive subtype of breast cancer for which chemotherapy had been the only active treatment option once metastatic disease developed. Immune checkpoint inhibitors (ICIs) are now available to treat patients with advanced TNBC who have programmed cell death ligand 1 (PD-L1)-positive tumors; these agents have been shown to improve clinical outcomes. Additionally, long-term disease control can be achieved in a subset of patients. Continued investigations of ICIs and optimal combinations with chemotherapy and targeted agents to enhance the immune response are ongoing, along with studies aimed at identifying the patients most likely to benefit. For early-stage TNBC, the data to date on administering ICI-based combination therapies in the neoadjuvant setting are compelling and suggest that the benefit from immunotherapy does not depend on PD-L1 expression. This review will discuss the clinical trial data on ICIs as monotherapy and in combination with chemotherapy in the treatment of patients with metastatic and early-stage TNBC.