The progress of combination therapy with immune checkpoint inhibitors in breast cancer

Immunotherapy targets the dysfunctional immune system to induce cancer cell killing by CD8-positive T cells. Immune checkpoint inhibitors (ICIs), specifically anti-PD-1 antibodies, anti-PD-L1 antibodies, and anti-CTLA4 antibodies, have revolutionized the management of many malignancies due to their significant role in generating a durable clinical response. However, clinical data suggest that response rates to ICI monotherapy are low due to the immunologically silent characteristics of breast cancer (BC). Chemotherapy, surgery, radiotherapy, and targeted therapy were recently reported to alter the tumor microenvironment and enhance the ICI response. Some clinical studies supported that ICIs, in combination with other treatment strategies, show superior efficacy in BC control, especially triple-negative breast cancer. Therefore, seeking a reasonable combination therapy is a promising way to improve ICI response. The present review highlights the clinical efficacy of ICIs treatment options in combination with standard-of-care therapies, such as chemotherapy and targeted therapy.