Background: In SOLO1 (NCT01844986), maintenance olaparib significantly improved progression-free survival (PFS) vs placebo (HR 0.30; 95% CI 0.23–0.41; Moore et al. N Engl J Med 2018) in pts with newly diagnosed advanced OC and a BRCAm. This analysis evaluates olaparib efficacy by timing of surgery, presence of residual tumor following surgery and response status after completion of chemotherapy in SOLO1. Methods: Pts underwent cytoreductive surgery and were in clinical complete response (CR) or partial response (PR) after platinum-based chemotherapy. Pts were stratified by response and received olaparib tablets 300 mg twice daily or placebo. Investigator-assessed PFS and objective response were assessed using modified RECIST v1.1. Results: 260 pts were randomized to olaparib and 131 to placebo; one pt did not receive placebo. Median follow-up was 41 months in both arms. 63% and 35% of pts underwent upfront and interval surgery, 21% and 76% had residual and no residual macroscopic disease after surgery, and 74% and 26% entered the study in clinical CR and PR (based on electronic case report form [eCRF] data). PFS was significantly improved regardless of the timing of surgery, residual disease status after surgery or response after platinum-based chemotherapy (Table). In pts with baseline radiologic evidence of disease (n=80; eCRF), the objective response rate was 43% for olaparib (CR, 28%) and 23% for placebo (CR, 12%). Conclusions: Maintenance olaparib improved outcomes compared with placebo in pts with newly diagnosed advanced OC and a BRCAm, regardless of surgical or tumor status. Clinical trial information: NCT01844986

*NED and a normal CA-125 level. ^†≥30% decrease in tumor volume or NED after chemotherapy but an abnormal CA-125 level. ^‡By eCRF. NED, no radiologic evidence of disease; NR, not reached; O, olaparib; P, placebo