Metastatic triple-negative breast cancer has a poor prognosis and poses significant therapeutic challenges. Until recently, limited therapeutic options have been available for patients with advanced disease after failure of first-line chemotherapy. The aim of this review is to assess the current evidence supporting second-line treatment options in patients with metastatic triple-negative breast cancer. Evidence was reviewed from controlled clinical trials in which eribulin, vinorelbine, capecitabine, gemcitabine, gemcitabine plus carboplatin, fam-trastuzumab-deruxtecan, sacituzumab govitecan, olaparib, and talazoparib were used in the second-line treatment for metastatic breast cancer, either as study drugs or as comparators. The benefit of treatment was evaluated using the European Society for Medical Oncology-Magnitude of Clinical Benefit Scale. Based on the evidence review, sacituzumab govitecan was identified as the preferred second-line treatment option for patients with metastatic triple-negative breast cancer, supported by clinical evidence and consensus across international clinical guidelines. Olaparib and talazoparib are of use in patients with human epidermal growth factor receptor 2-negative metastatic breast cancer and germline BRCA1/2 mutations. Exploratory data for fam-trastuzumab-deruxtecan suggest a survival benefit in human epidermal growth factor receptor 2-low, hormone-receptor-negative patients, but further solid evidence is required. Other chemotherapies with lower European Society for Medical Oncology-Magnitude of Clinical Benefit Scale scores may continue to be useful in highly selected patients.
