Efficacy of niraparib maintenance therapy in Chinese women with platinum-sensitive recurrent ovarian cancer with and without secondary cytoreductive surgery: Results from the NORA trial.

5534 Background: NORA is the first, phase III, randomized controlled trial (RCT) that demonstrated individualized starting dose regimen of niraparib, which significantly improved PFS in Chinese patients with platinum-sensitive recurrent ovarian cancer (PSROC). This sub-group analysis evaluated the efficacy of niraparib maintenance therapy with and without secondary cytoreductive surgery (SCS) in PSROC. Methods: The NORA phase III RCT included adult (≥18 years) Chinese women with PSROC who were randomized in a 2:1 ratio to receive oral niraparib (n = 177) or matched placebo (n = 88). This retrospective subgroup analysis was based on the progression-free survival (PFS) of niraparib maintenance therapy in these two groups of patients with PSROC, patients with SCS, and patients without SCS. The PFS was assessed by blinded independent central review. The Kaplan-Meier (KM) estimator and log-rank test were performed to calculate the median PFS time. Results: Of the 265 evaluable patients, 69 (26.0%) patients received the SCS (niraparib, n = 48; placebo, n = 21), and 196 (74.0%) patients were without SCS (niraparib, n = 129; placebo, n = 67). Among patients with and without SCS, baseline characteristics for BRCA mutation were 26.1% vs 41.8%, complete response to last platinum-based chemotherapy were 68.1% vs 43.9%, time (6-12 months) to progression after penultimate therapy were 23.2% vs 34.7%, respectively. Treatment with niraparib led to a significant reduction of risk to disease progression compared with placebo in patients with SCS (Hazard ratio [95% CI]: 0.32 [0.13–0.78]; P = 0.0102) and without SCS (0.34 [0.23–0.50]; P< 0.001). Moreover, in the subgroups of patients who received SCS, niraparib maintenance therapy had a significantly longer PFS compared with placebo (Median [95% CI]: not reached [18.33 – not estimable] vs 5.75 months [3.68 – not estimable]; P = 0.0102). This trend was also similar in the subgroup of patients who did not receive SCS (Median [95% CI]: 10.28 months [7.49 – 18.37] vs 4.90 months [3.71 – 5.52]; P < 0.0001). Conclusions: The results from this retrospective sub-group analysis revealed that niraparib maintenance therapy provided significant clinical efficacy in patients with PSROC, irrespective of SCS. Clinical trial information: NCT03705156.