Immunotherapy in Triple-Negative Breast Cancer

Currently, immunotherapy has led to a paradigmatic shift in the treatment of many cancer types, including triple-negative breast cancer. Immunotherapy increases the efficacy of the immune system in treating cancer, with a durable effect due to immunologic memory. The PD-1 inhibitor, pembrolizumab, combined with neoadjuvant chemotherapy, improved event-free survival and is a new standard of care for patients with high-risk, early stage triple-negative breast cancer (TNBC), regardless of tumor PD-L1 expression. For metastatic TNBC, pembrolizumab combined with chemotherapy is a new standard of care for first-line therapy for PD-L1⁺ metastatic TNBC, and it improves overall survival. The PD-L1 inhibitor, atezolizumab, combined with nab-paclitaxel, is also approved for first-line treatment of metastatic PD-L1⁺ TNBC. The aim of this review is to examine the existing evidence and ongoing studies on immunotherapy in patients with early stage and metastatic triple-negative breast cancer (TNBC), including new combination strategies with several drugs, such as chemotherapy, targeted therapy, or radiation and to discuss immune checkpoint inhibitor (ICI) applications and the possibility of emerging strategies in different TNBC stages.