Triple-negative breast cancer (TNBC) is an aggressive form lacking estrogen, progesterone, and HER2 receptors, which historically limited treatment to chemotherapy. Recent advances in immunotherapy have transformed care, especially because TNBC tumors are often more immunogenic, with higher levels of tumor-infiltrating lymphocytes and PD-L1 expression that make them responsive to immune-targeting treatments.
Checkpoint inhibitors are the main immunotherapy option for TNBC. Pembrolizumab (Keytruda) is FDA-approved for both early-stage and advanced disease. In high-risk early-stage TNBC, it is combined with neoadjuvant chemotherapy and continued as adjuvant monotherapy, improving response rates and event-free survival. For advanced PD-L1-positive tumors, pembrolizumab is used with chemotherapy. Atezolizumab (Tecentriq) previously established immunotherapy’s role in metastatic TNBC. PD-L1 testing guides therapy for advanced disease, though early-stage high-risk patients receive treatment regardless of PD-L1 status.
Ongoing research aims to enhance outcomes for non-responders by combining immunotherapy with antibody-drug conjugates, PARP inhibitors, cancer vaccines, adoptive cell therapy, and oncolytic viruses.