795P Tolerability and Effectiveness of Niraparib in Long-Term Responders with Platinum-Sensitive Recurrent Ovarian Cancer (GEICO-88R Study)

The GEICO-88R study assessed the real-world use of niraparib as maintenance treatment in patients (pts) with platinum-sensitive recurrent high-grade ovarian cancer (OC) within the Spanish expanded access program. A preplanned sub-analysis of long-term responders (LTR) is presented. In this retrospective study across 57 Spanish sites pts received niraparib at a fixed starting dose (FSD) of 300 mg/day or individualized starting dose (ISD) according to weight and platelet count. A specific assessment of LTR to niraparib maintenance treatment (exposure ≥1 year) was performed, describing patient characteristics, niraparib dosing, tolerability, and effectiveness. This sub-analysis included 107 pts (33.8% of 316 from general study), with median age 64 years (43-88) and a median of 2 previous lines (53.3% 1-2, 46.7% ≥3). Main initial FIGO stages were III (58.8%) and IV (18.6%). Forty-five (42%) pts received prior bevacizumab and 81.3% were gBRCAwt. 99 pts had surgery at primary diagnosis (72.7% primary and 27.3% interval debulking), R0 in 69.9%. 31 (29%) pts had surgery at relapse, R0 in 64.5%. At baseline, ECOG was 0 (56.1%) or 1 (43.9%). Relevant comorbidities were reported in 46.7% of pts. Niraparib was initiated at FSD in 24 pts and at ISD in 83 (80.7% at 200 mg/day; 19.3% at 300 mg/day). Overall median dose was 200 mg. Median treatment duration was 26.2 months (12-60.7). 68.2% of pts required at least one dose interruption or reduction. 39 (36.4%) pts remained on treatment upon analysis (91.1% discontinued due to progression, 2.9% toxicity, and 4.4% physician/patient decision). The most frequent all-grade adverse events were thrombocytopenia (42.1%), anemia (36.4%), and asthenia (29.9%), with no significant differences between FSD vs ISD pts. Of 85 pts with pre-niraparib measurable disease, PR+CR was 63.5%. With median follow-up of 29.95 months, median PFS, PFS2 an OS were 27.2 (95% CI 23.6- 29.6), 42.3 (95% CI 34.2-NA) and not reached (85.4% of pts alive). A durable response was achieved in a substantial proportion of pts, even despite the high risk of this population (majority BRCAwt, pre-treated, significant comorbidities) with a good tolerability profile in a real-world setting.