Olaparib Maintenance Therapy in Metastatic Breast Cancer

Olaparib, a PARP inhibitor, is proven as an effective therapy for germline BRCA1/2-mutated breast cancer; however, the therapeutic efficacy for somatic mutation in BRCA1/2 or genes of homologous recombination DNA repair is unclear. Maintenance of Oalaprib can delay the disease progression in patients with BRCA1/2 mutated advanced ovarian cancer after treatment with platinum based chemotherapy. The investigators design a phase 2 study to evaluate the efficacy of maintenance of Olaparib in patients with metastatic breast cancer. The investigators enroll patients with metastatic ER(+)Her2(-) or triple-negative breast cancer. Patients who are chemotherapy-naïve or prior 1-line chemotherapy are eligible for screening. All eligible patients will receive 4 cycles of platinum based chemotherapy. Gene test will be performed on their breast tumor. If patients have mutation of HR genes and at least stable disease after platinum based chemotherapy, they will be randomized to treatment arm (Olaparib maintenance) or control arm (continuation of chemotherapy). The primary end-point is progression-free survival, and the secondary end-point is to assess the response rate, overall survival and quality of life.