PD‑L1/PD‑1 blockade in breast cancer: The immunotherapy era (Review).

Breast cancer is a common malignant tumor in women. Triple‑negative breast cancer (TNBC) is highly invasive with a high rate of metastasis and poor prognosis. Programmed death ligand 1 (PD‑L1) plays an important role in mediating the escape of tumor cells from immune surveillance. There have been significant advances in understanding the biology of TNBC. This review presents a detailed discourse on the available data on the expression of PD‑L1 in breast cancer and preliminary clinical outcome of PD‑L1/PD‑1 inhibitors in breast cancer patients. Early clinical trials involving PD‑L1/PD‑1 inhibitors have exhibited efficacy in tumor response and/or disease control in patients with refractory metastatic breast cancer, particularly TNBC. Furthermore, the mechanisms and factors that influence the immunoediting process are summarized and their functions in detail are analyzed.