Real-world effectiveness of first-line niraparib maintenance therapy in Korean patients with advanced ovarian cancer: A multicenter retrospective cohort study.

e17562 Background: Although first-line maintenance therapy with poly(ADP-ribose) polymerase (PARP) inhibitors has significantly improved progression-free survival in advanced epithelial ovarian cancer, the overall survival benefit of niraparib remains uncertain in randomized trials, largely due to substantial post-progression crossover to PARP inhibitors. Real-world data from clinical settings with limited crossover may therefore provide a more appropriate assessment of the survival impact of niraparib, particularly in underrepresented Asian populations. Methods: This multicenter, retrospective cohort study included patients with newly diagnosed FIGO stage III–IV EOC who completed first-line platinum-based chemotherapy between December 2019 and October 2022 at nine tertiary institutions in South Korea. Patients were categorized into those receiving niraparib maintenance and those with no maintenance. Propensity score matching (PSM) adjusted for baseline differences including age, neoadjuvant chemotherapy, and BRCA mutation status. Primary endpoints were progression-free survival (PFS) and overall survival (OS), analyzed using Kaplan–Meier and Cox models with predefined subgroup analyses. Results: A total of 554 patients were included (niraparib, n=248; no maintenance, n=306). In the unmatched cohort, niraparib was associated with significantly longer PFS (p=0.00017) and OS (p=0.0011). After 1:1 PSM, 189 matched pairs were analyzed. The 3-year PFS rate was higher with niraparib (43.1% vs. 25.7%; p=0.00011), as was the 3-year OS rate (86.3% vs. 74.7%; p=0.0046). Subgroup analyses showed PFS benefit in both BRCA-mutated (60.3% vs. 37.1%; p=0.0071) and BRCA wild-type patients (35.4% vs. 23.0%; p=0.017). OS benefit was evident in BRCA wild-type (p=0.017) but not BRCA-mutated patients (p=0.47). Crossover to subsequent PARP inhibitors occurred only in the no-maintenance group, more frequently in BRCA-mutated tumors (21.4%) than wild-type (4.1%). Niraparib benefit was most pronounced in patients undergoing primary debulking surgery with complete cytoreduction. Conclusions: First-line niraparib maintenance improved PFS regardless of BRCA status. OS benefit was observed in the matched cohort, particularly among BRCA wild-type patients with minimal crossover to post-progression PARPi.