An exploratory analysis about cycles of adjuvant chemotherapy and outcomes by substage for stage I ovarian clear cell carcinoma: a single institution retrospective study.

This retrospective cohort study was designed to explore the prognostic impact of adjuvant chemotherapy and tumor substage on stage I ovarian clear cell carcinoma (OCCC). Data of 102 patients with stage I OCCC who underwent surgery at the National Cancer Center/Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College from February 1999 to December 2018 was retrospectively analyzed. Prognostic factors were evaluated using the Cox Regression Model. The disease-free survival (DFS) and overall survival (OS) were assessed by the Kaplan-Meier method and compared between different groups with the log-rank test. P < 0.05 was considered statistically significant. The median follow-up duration was 40.5 months. Thirty-one (30.4%) patients were at stage IA, and 17 (16.7%), 5 (24.5%) and 17 (16.7%) patients were at stage IC1, IC2 and IC3 respectively. The 5-year and 10-year DFS rates of the entire cohort were 82.8% and 78.8% respectively, and the 5-year OS was 97.9%. Patients at stages ICI (intraoperatively ruptured tumor) and IA had similar DFS (P=0.538, OR=0.024), and that of patients at stages IC2 (tumor ruptured preoperatively or tumor on ovarian surface) or IC3 (ascites or peritoneal washings with positive cytology) was significantly lower (72.6% vs. 95.1%, P=0.039, OR=5.051). The 5-year DFS of patients receiving four (83.9%) and more than four (81.7%) cycles adjuvant chemotherapy were similar. Furthermore, univariate analysis showed that age, tumor size and CA199 levels were significantly correlated with DFS, although none of these variables were identified as independent prognostic factors in the multivariate analysis. In summary, our results suggest that patients with stage I OCCC have overall good prognosis. However, tumor surface involvement or positive cytology can worsen prognosis, and the prognosis may not be improved by more than four cycles chemotherapy following surgery. The remarkable increased CA199 may be a potential indicator of poor prognosis in stage I OCCC.