Adjuvant Chemotherapy in Stage I Ovarian Clear Cell Carcinoma: A Systematic Review and Meta-analysis.

Abstract

To investigate the treatment effect of adjuvant chemotherapy for stage I ovarian clear cell carcinoma. We searched Cochrane, PubMed, International Standard Randomised Controlled Trial Number registry, ClinicalTrials.gov, the World Health Organization International Clinical Trials Registry Platform, and Ichushi-Web to January 22, 2025. We included randomized controlled trials (RCTs) and non-RCTs that included more than 50 patients with stage I ovarian clear cell carcinoma. The primary and secondary outcomes were disease-free survival and overall survival, respectively. We performed a meta-analysis of the stage-adjusted hazard ratios (HRs) of adjuvant chemotherapy compared with placebo or no intervention. The substage-related heterogeneity of effects was also assessed. A meta-analysis of proportions was also conducted to assess 5-year disease-free survival and 5-year overall survival. Risk of bias was assessed with the Risk of Bias in Non-randomized Studies of Interventions tool. Because no RCTs reported HRs for the ovarian clear cell carcinoma subgroup, data from nine non-RCTs were analyzed. The pooled substage-adjusted HR for disease-free survival associated with use of chemotherapy was 0.47 (95% CI, 0.29-0.74) and that for overall survival was 0.66 (95% CI,0.43-1.00). Heterogeneity in the effect by substage was not evident for either disease-free survival (P for subgroup difference=.91) or overall survival (P=.60). The pooled 5-year disease-free survival was 0.80 (95% CI, 0.65-0.89) for stage I overall, 0.95 (95% CI, 0.47-1.0) for stage IA, and 0.61 (95% CI, 0.47-0.74) for stage IC. The estimated number needed to treat was 10.2 (95% CI, 5.8-18.6) for stage I overall, 40.8 (95% CI, 3.9-infinity) for stage IA, and 5.2 (95% CI, 3.9-7.8) for stage IC. Adjuvant chemotherapy improves disease-free survival and may prolong overall survival in patients with stage I ovarian clear cell carcinoma. Available evidence suggests that recurrence is reduced by approximately 50%. Treatment decisions should consider the baseline recurrence risks and absolute benefits. PROSPERO, CRD42024562486.