[The evolution of a luminal breast cancer to a triple-negative and its impact on disease control with sacituzumab govitecan.]

Triple negative breast cancer (TNBC) represents 15% of invasive breast cancer cases and is an aggressive subtype. Patients with metastatic TNBC have a poor prognosis. Efforts have been made to develop new therapeutic options and identify molecular biomarkers to improve overall survival and quality of life for TNBC patients. Immunotherapy has shown promising frontline clinical activity. To determine which patients will derive the most benefit from a combination of immune checkpoint inhibitors and chemotherapy in metastatic disease, it is essential to evaluate PD-L1 expression. Approximately 15% of TNBC patients have a germline mutation in BRCA1 and/or BRCA2, and for these patients, innovative therapeutic options such as olaparib and talazoparib, which are PARP inhibitors, are available. Sacituzumab govitecan (SG) is a humanized monoclonal antibody-drug conjugate directed against the surface antigen of human trophoblastic cells (Trop-2) expressed in approximately 90% of TNBC, coupled with SN-38, the active metabolite of irinotecan, a topoisomerase I inhibitor. Here, we present the case of a woman who was initially diagnosed with localized luminal B breast cancer (ER-positive; HER2-negative) and was treated with curative therapy. However, she later experienced a recurrence with metastatic TNBC (ER-negative/HER2-negative) and received treatment with sacituzumab govitecan, which resulted in prolonged disease control.