RT Journal Article SR Electronic T1 O017/#15 Efficacy and safety of niraparib maintenance treatment in platinum-sensitive recurrent ovarian cancer after shorter or longer chemotherapy: a post hoc subgroup analysis JF International Journal of Gynecologic Cancer JO Int J Gynecol Cancer FD BMJ Publishing Group Ltd SP A10 OP A11 DO 10.1136/ijgc-2021-IGCS.17 VO 31 IS Suppl 4 A1 Y Gao A1 X Wu A1 J Zhu A1 R Yin A1 J Yang A1 J Liu A1 J Wang A1 L Wu A1 Z Liu A1 D Wang A1 G Lou A1 H Yang A1 Q Zhou A1 B Kong A1 Y Huang A1 L Chen A1 G Li A1 R An A1 T Tan A1 J Dong YR 2021 UL http://ijgc.bmj.com/content/31/Suppl_4/A10.2.abstract AB Objectives Traditionally ≥6 cycles of platinum-containing chemotherapy (Pt-chemo) are recommended for platinum-sensitive recurrent ovarian cancer (PSROC). PARP inhibitor maintenance treatment (MT) can be initiated upon clinical complete/partial response (CR/PR) after ≥4 cycles of chemotherapy. Shorter chemotherapy may improve patient experience without compromising efficacy. This study aims to compare the efficacy and safety of niraparib to placebo as MT administered after ≤4 or >4 cycles of Pt-chemo.Methods This is a post hoc analysis of the published NORA phase III study (NCT03705156). Adults with PSROC and CR/PR to most recent Pt-chemo were randomized 2:1 to niraparib or placebo. Primary endpoint was PFS by BICR. Subgroups comprised patients with ≤4 or >4 cycles of most recent Pt-chemo.Results Table 1 summarizes key baseline characteristics which were overall balanced between groups. Median (95% CI) PFS was 18.37 months (8.54–not estimable [NE], ≤4-cycle/niraparib) versus 3.88 months (3.68–7.43, ≤4-cycle/placebo; HR=0.36 [p=0.0016]), and was 18.33 months (10.28–NE, >4-cycle/niraparib) versus 5.49 months (3.71–5.75, >4-cycle/placebo; HR=0.33 [p<0.0001]) (figure 1). Overall safety profiles were comparable between ≤4-cycle/niraparib and >4-cycle/niraparib, with similar percentages of patients experiencing neutrophil count decrease (60.4%; 58.1%), anemia (50.0%; 55.0%), and platelet count decrease (45.8%; 58.1%). Composition of grade ≥3 TEAEs was consistent with the overall NORA results.View this table:Abstract O017/#15 Table 1 Key baseline characteristics for subgroups with ≤4 or >4 treatment cycles of most recent PT-chemoAbstract O017/#15 Figure 1 PFS by blinded independent central review (interaction-to-treat)Conclusions Similar niraparib-versus-placebo PFS benefits were observed after ≤4-cycle or >4-cycle Pt-chemo in CR/PR patients. The efficacy and safety of niraparib MT after shorter Pt-chemo remain to be verified in larger samples.