Abstract
Triple-negative breast cancer poses distinct challenges because it lacks hormone receptors and does not have human epidermal growth factor receptor 2 (HER2) amplification. Mutations in BRCA1/2 genes are associated with homologous recombination deficiency tumors, rendering them susceptible to poly (ADP-ribose) polymerase (PARP) inhibitors. Notably, germline BRCA1/2 mutations are linked to distinct clinical features, including an increased risk of triple-negative breast cancer (TNBC) and a younger age of onset. PARP inhibitors such as olaparib and talazoparib have demonstrated efficacy in patients with BRCA mutations, leading to FDA approvals for ovarian and breast cancers. However, there remains limited data on PARP inhibitor response rates in patients with somatic BRCA mutations. This case series demonstrates the use of rucaparib in metastatic breast cancer patients harboring both germline and somatic BRCA1/2 mutations, discussing the advancing landscape of targeted therapies in breast cancer management. In the first case, despite undergoing anthracycline-based chemotherapy followed by hormonal therapy, disease progression ensued. However, transitioning to rucaparib yielded a remarkable complete response lasting over two years, highlighting its efficacy in this clinical setting. Similarly, in the second case, rucaparib demonstrated effectiveness as a maintenance therapy subsequent to achieving a near-complete response to taxane and platinum-based treatment. These findings emphasize the promising role of rucaparib in managing metastatic breast cancer in patients with BRCA1/2 mutations, further contributing to the expanding armamentarium of targeted therapies in breast cancer care.