Background: In the Phase III PAOLA-1/ENGOT-ov25 trial, maintenance olaparib + bevacizumab (bev) provided a significant progression-free survival (PFS) benefit vs placebo (pbo) + bev in patients (pts) with newly diagnosed advanced ovarian cancer in response to platinum-based chemotherapy. Subgroup analyses revealed a substantial PFS benefit in homologous recombination deficiency (HRD)-positive (including BRCA1/2 mutation) pts, leading to US/EU labels for this combination. Preliminary analyses reported that olaparib did not alter global health-related quality of life (G-HQoL; Ray-Coquard I et al. NEJM 2019). We analyzed HQoL by domains and molecular subgroups and explored the impact of disease progression (DP) on HQoL in the 1L setting. Methods: Eligible pts with newly diagnosed advanced (FIGO stage III?IV) HGOC were randomized 2:1 to maintenance olaparib + bev or pbo + bev. Pts completed European Organisation for Research and Treatment of Cancer QLQ-C30 and QLQ-OV28 HQoL questionnaires at baseline and every 12 weeks for 2 years? follow-up, irrespective of DP. The minimal important difference for clinically relevant change was fixed at 10 points. Longitudinal data were analyzed by mixed model for repeated measures (MMRM) and time until definitive deterioration (TUDD). Analyses were in the intent-to-treat population and HRD-positive subgroup. HQoL analyses at DP (± 60 days) were explored. Results: 806 pts were randomized to olaparib + bev (n=537) or pbo + bev (n=269). 465 pts had DP over 2 years? follow-up. Compliance to HQoL questionnaires was high at baseline (95%) and over time (>70%). MMRM models by HQoL domain did not reveal a clinically relevant difference between treatment arms over time. TUDD of G-HQoL did not differ between arms (hazard ratio [HR] 0.88, 95% confidence interval [CI] 0.72?1.07). In the HRD-positive subgroup (n=372), we observed no difference by HQoL domain between treatment arms. Interestingly, TUDD of G-HQoL was statistically significantly in favor of olaparib + bev compared with pbo + bev (HR 0.70, 95% CI 0.52?0.93). We also observed a clinically significant deterioration in emotional (mean change −12.30 points, 95% CI −16.46 to −8.13) and social (−11.17 points, 95% CI −16.21 to −6.12) functioning in both treatment arms at DP, among 103 pts with HQoL questionnaires at DP. Conclusions: The substantial PFS benefit provided by maintenance olaparib + bev in the newly diagnosed setting was achieved without detrimental effect on HQoL domains, even with longer TUDD of G-HQoL in the HRD-positive subgroup. Use of an effective maintenance therapy (ie one with a significant PFS benefit) in HGOC patients in the 1L setting is likely to delay the clinically significant deterioration in emotional and social functioning we identified in patients at DP across PAOLA-1 treatments arms. Clinical trial information: NCT02477644.