1199 Efficacy of bevacizumab versus PARP inhibitors as maintenance therapy after first-line platinum-based chemotherapy for homologous recombination proficient, advanced high-grade ovarian cancer patients: a retrospective study

Introduction/Background Homologous Recombination deficiency (HRd) testing is an essential tool to tailor the maintenance treatment strategy after first-line, platinum-based chemotherapy for advanced high-grade ovarian cancer (aHGOC) patients. Bevacizumab and PARP inhibitors (PARPi) monotherapy are alternative options for the Homologous Recombination proficient (HRp) population. However, there is no direct comparison between the two therapeutic options in previous studies. Methodology We retrospectively analyzed 84 HRp aHGOC patients (serous/endometrioid) treated with bevacizumab or PARPi as first-line maintenance therapy at Fondazione Policlinico Universitario A. Gemelli, IRCCS. We assessed the efficacy of bevacizumab versus PARPi in terms of progression-free survival (PFS) and overall survival (OS). Median PFS (mPFS) and OS (mOS) were calculated using the Kaplan-Meier method. Cox proportional-hazards model was used to calculate hazard ratio (HR) and 95% confidence intervals (95%CI). Results Forty-eight HRp aHGOC patients were treated with bevacizumab and 36 with PARPi. No differences were found between the two groups in PFS (mPFS: 13.8 with bevacizumab vs. 14.4 months with PARPi; HR 0.67 95%CI, 0.40–1.12; p=0.13) and OS (mOS: 35.2 with bevacizumab vs. 33.1 months with PARPi; HR 0.98 95%CI, 0.42–2.31; p>0.9) after a median follow-up of 23.7 months. Considering the high-risk subpopulation (FIGO stage IVB, neoadjuvant chemotherapy, unresectable disease, residual disease at surgery), 32 patients were treated with bevacizumab and 34 with PARPi. No statistically significant differences in PFS (mPFS = 13.8 with bevacizumab vs. 14.4 months with PARPi; HR 0.69 95%CI 0.39–1.23, p=0.2) and OS (mOS = not reached with bevacizumab vs. 33.1 months with PARPi; HR 0.85 95%CI 0.27–2.67, p=0.8) were observed. Conclusion No differences in terms of efficacy were found between bevacizumab and PARPi as first-line maintenance treatment for HRp aHGOC patients (both all comers and high-risk sub-population). More robust data are warranted to confirm our findings. In this context, results from the randomized, phase 2, MITO25.1 trial are urgently awaited. Disclosures V.S. reports Honoraria/consultation fees from AstraZeneca, MSD, GSK, Pharmamar and Novocure. D.L. reports consulting or advisory role at PharmaMar, Merck Serono, Novartis; speakers' bureau fees from AstraZeneca, Clovis Oncology, PharmaMar, and Tesaro/GSK; research funding (to institution) from Clovis Oncology, Merck, PharmaMar, and Tesaro/GSK; personal financial interest in AstraZeneca, Clovis Oncology, PharmaMar, Roche, and Tesaro/GSK; Honoraria from AstraZeneca, Clovis Oncology, Genmab, Immunogen, Merck, Roche, and Tesaro/GSK; Expert testimony on behalf of Clovis Oncology. G.S. reports Honoraria/consultation fees from Covidien AG, AstraZeneca, MSD, speakers' bureau fees from Olympus Europa, Baxter Healthcare, Intuitive Surgical Inc., GlaxoSmithKline. A.F. reports Honoraria/consultation fees from Johnson&Johnson, research grants/supports from AstraZeneca, speakers' bureau fees from Fondazione Interazionale Menarini. C.M. reports Honoraria/consultation fees from AstraZeneca and Pharmamar, research grants/supports from AstraZeneca, Pharmamar, MSD, GSK, and Menarini. E.G, L.V., G.M.I, A.P., V.G., C.M.S., R.E., M.D. have nothing to disclose.