Checkpoint inhibitors in triple-negative breast cancer (TNBC): Where to go from here

Advances in cancer immunotherapy and a growing body of research have focused on the role of the antitumor response in breast cancer. Triple-negative breast cancer (TNBC) is the most immunogenic breast cancer subtype, and there is strong evidence that tumor-infiltrating lymphocytes in TNBC have prognostic value and are associated with clinical outcome and improved survival. Evading antitumor immunity is a hallmark for the development and progression of cancer. Immunotherapy studies have focused on the role of the programmed cell death-1 (PD-1) receptor/programmed death-ligand 1 (PD-L1) pathway in maintaining immunosuppression in the tumor microenvironment. Blockade of the PD-1/PD-L1 axis has emerged as a promising therapeutic option to enhance antitumor immunity and is actively being investigated in TNBC, with encouraging results. In this article, the authors review the current literature on checkpoint inhibitors in TNBC with a focus on PD-1/PD-L1 antibodies and discuss combination strategies and novel approaches for improving antitumor immunity and clinical outcome. Cancer 2018;124:2086-103. © 2018 American Cancer Society.