582 CA125 and platinum free interval as potential predictive biomarkers of PARP inhibitors’ effectiveness in platinum-sensitive recurrent ovarian cancer: a multicentric retrospective analysis

Introduction/Background In platinum-sensitive recurrent ovarian cancer (PSROC) patients, PARP inhibitors (PARPis) represent the first choice for maintenance therapy (if PARPis naïve). Several real word data suggested that a normalized CA125 at baseline, as well as a longer prior platinum free interval (PFI) could be predictive of a better outcome patients in PARPis era. Methodology This is a real-world multicenter retrospective analysis including high grade serous and endometrioid PSROC patients who received PARPis after complete or partial response to platinum-based chemotherapy at the time of first or second recurrence. The objective of this exploratory analysis was to describe the predictive role of CA125 and PFI on the effectiveness of PARPi as maintenance therapy in a relapsed setting, in terms of progression free survival (PFS) and overall survival (OS). Results Clinical data from a dataset including 519 patients were analyzed, among them 36% were BRCA 1–2 mutated. Cut off for CA125 normal value was settled at 12 m) seemed to benefit more from PARPi therapy than partially platinum sensitive patients (PFI: 6–12 months) both in terms of PFS (17 vs 9.6 months) and OS (not reached vs 24.9). Controversially BRCA status didn't impact PFS and OS. Conclusion Considering the limitations related to retrospective study, our data supports a maximal benefit from PARPi-based therapy in a population with a normal CA 125 value at baseline and a longer prior PFI. Disclosures The authors declare no disclosures.