Predictive factors for prolonged response to olaparib as maintenance therapy in ovarian cancer patients with BRCA mutations.

5558 Background: To investigate clinical factors predictive for prolonged progression-free survival (PFS) in ovarian cancer (OC) patients carrying BRCA mutations and receiving olaparib as a maintenance therapy. Methods: Multicentric (7 cancer centers) international (France and Switzerland) retrospective study of OC patients having germline or somatic mutations of BRCA1/BRCA2 genes and treated with olaparib as maintenance therapy after platinum-based chemotherapy. Results: One hundred and fifteen patients were included. Median age was 60 years. There were 92 BRCA1 carriers, 22 BRCA2 carriers and one patient had double mutation of BRCA1 and BRCA2 genes. Ninety-two percent had serous carcinomas. Six patients had somatic mutations (all BRCA1) and 109 had germline mutations. Median follow-up was 9.8 months. Ninety percent of the patients were platinum-sensitive: 24% had platinum-free interval (PFI) at 6-12 months and 65% had PFI > 12 months. Responses to platinum-based chemotherapy before olaparib as maintenance therapy were: SD (15.7%), PR (52.2%) and CR (32.2%). In multivariate analysis, factors predictive for prolonged PFS under olaparib were: CR (HR = 0.13; 95%CI 0.06-0.28; p< 10-3), PFI > 12 months (HR = 0.43; 95%CI 0.26-0.73; p= 0.002) and BRCA2 mutations (HR = 0.42; 95%CI 0.24-0.94; p= 0.033). Conclusions: Complete response to platinum before olaparib, PFI > 12 months, and BRCA2 mutations are predictive for prolonged PFS in BRCA carriers who received olaparib as maintenance therapy.