Adjuvant taxane plus platinum chemotherapy for stage I ovarian clear cell carcinoma with complete surgical staging: are more than three cycles necessary?

Previous studies on adjuvant chemotherapy for patients with ovarian clear cell carcinoma (OCCC) have included a limited number of Asian patients with surgical stage I OCCC, despite differences in OCCC survival by race and stage. The aim of this study was to estimate the survival effect of the number of cycles of adjuvant taxane plus carboplatin chemotherapy in Asian patients with surgical stage I OCCC. We retrospectively identified 227 patients with surgical stage I OCCC at 14 institutions from 1995 to 2017. Kaplan–Meier analysis and Cox proportional hazard regression with inverse probability of treatment weighting (IPTW) adjustment were performed to evaluate overall survival (OS) and recurrence-free survival (RFS) in patients receiving ≤ 3 and 4–6 cycles of taxane plus platinum adjuvant chemotherapy. Eighty-nine and 138 patients received ≤ 3 and 4–6 cycles of adjuvant chemotherapy, respectively. There was no between-group difference in OS or RFS with or without IPTW adjustment. In Cox proportional hazards analysis, 4–6 cycles of adjuvant chemotherapy were not associated with improved OS (HR 1.090; 95% CI 0.518–2.291; p = 0.821) or RFS (HR 1.144; 95% CI 0.619–2.114; p = 0.669) compared to ≤ 3 cycles, even with IPTW adjustment. Subgroup analysis in different substages of stage I OCCC showed that the number of cycles of adjuvant chemotherapy had no impact on OS or RFS. Three or fewer cycles of taxane plus carboplatin chemotherapy may be a reasonable treatment regime for patients with surgical staging I OCCC.