Immunotherapy with anti-PD-1 or PD-L1 in advanced ovarian cancer (OC): A meta-analysis of randomized trials.

5570 Background: Immunotherapy (IO) has shown promising results in several solid tumors, including gynaecological malignancies. While PARP inhibitors and bevacizumab had deeply improved outcomes in OC, prognosis remains poor, underscoring the need for innovative treatment strategies. Anti-PD-1 and PD-L1 monoclonal antibodies have been evaluated in randomized trials across both first-line and recurrent OC settings. This meta-analysis summarizes the available evidence to assess progression-free survival (PFS) benefits from IO-based strategies. Methods: Phase II and III randomized clinical trials (RCTs) evaluating IO-based strategies using PD1 or PDL1 inhibitors published between 2019 and 2024 were identified through PubMed, Embase, and the Cochrane Library, as well as conference proceedings. Eight trials with PFS as primary endpoint, conducted in first-line and recurrence settings, were included. Data on PFS by PD-L1 status were available in seven trials. Three trials included two experimental arms and were analysed separately. Hazard ratios (HRs), 95% confidence intervals (CIs), and PFS events were extracted for overall populations and subgroups. A random-effects model was employed for data analysis, with sensitivity analyses performed to explore outcome variability. Results: The meta-analysis included 8 trials comprising 6,205 patients. The addition of IO to chemotherapy or placebo showed no improvement in PFS (HR = 1.02, 95% CI 0.86-1.22). Subgroup analyses indicated no significant differences in PFS in first-line (HR = 0.99, 95% CI 0.78-1.26) or recurrence settings (HR= 1.07, 95% CI 0.80-1.44). In trials reporting PD-L1 status (47.5% PD-L1 positive population), IO-based therapies demonstrated a non-significant trend towards PFS improvement (HR = 0.94, 95% CI 0.77-1.13). Excluding IO-only arms yielded similar results (HR = 0.94, 95% CI 0.79-1.11). Conclusions: IO-based strategies did not provide a substantial PFS benefit in advanced OC, irrespective of disease setting or PD-L1 status. Identifying effective combination strategies and patient subgroups that may benefit from IO remains an open research question.