Response of Estrogen-Receptor-Positive Metastatic Breast Cancer to Olaparib in Late-Line Therapy

Monotherapy with olaparib provides significant benefits over standard therapy in patients with a germline BRCA mutation and human epidermal growth factor receptor 2 (HER2) negative metastatic breast cancer, who had two or fewer previous chemotherapeutic regimens for metastatic disease. Olaparib was approved on July 2, 2018, in Japan for the treatment of patients with metastatic breast cancer with a BRCA mutation and HER2-negative status. Thus, the current experience with this drug is relatively limited. In this article, we report a case of luminal-type metastatic breast cancer harboring a BRCA1 mutation detected through BRACAnalysis (Myriad Genetics). Despite the late-line treatment, in this patient, olaparib was effective against metastatic breast cancer.