A Two-stage Simon Design Phase II Study for Non-BRCA MBC Patients With HRD Treated With Olaparib Single Agent

This is an international, multi-centre, non-controlled, open-label, single arm, two-stage Simon Design phase II study for non-BRCA metastatic breast cancer (MBC) patients with homologous recombination deficiency treated with Olaparib single agent. The main objective is to assess the efficacy of olaparib single agent as determined by Clinical Benefit Rate (CBR) using the Response Evaluation Criteria in Solid Tumors (RECIST 1.1). In the first stage Triple negative (TN) non-BRCA, metastatic breast cancer (MBC) patients whose tumours exhibited any characteristic related to homologous recombination deficiency (HRD). In the second stage, luminal patients (RH positive HER2 negative) will be allowed in the same conditions that TN. Patients whose tumours are identified as Homologous Recombination Deficient by deleterious HRR gene mutations (according to Foundation Medicine's Foundation One assay) will receive olaparib 300 mg (two tablets of 150mg) orally twice daily (bid) on days 1-28 each 28 days. Study commitment is 39 patients: 17 patients will be enrolled at first stage and 22 at the second stage. The total duration of the study period is 34 months.