Less impact of adjuvant chemotherapy for stage I clear cell carcinoma of the ovary: a retrospective Japan Clear Cell Carcinoma Study.

Introduction: Ovarian clear cell carcinoma (CCC) is regarded as grade 3 tumor, and the National Comprehensive Cancer Network (NCCN) Clinical Practice Guidelines recommend adjuvant chemotherapy for the tumor even at stage IA. However, CCC often showed chemo-resistant phenotype, and the effect of adjuvant chemotherapy still remained uncertain. Methods: Clear cell carcinoma cases treated at collaborating institutions during the period 1992-2005 were retrospectively identified. After a central pathological review, survival analysis was estimated by the Kaplan-Meier method, and prognostic factors were evaluated using a Cox regression model. Results: Among 219 patients with stage I CCC, 195 patients received adjuvant chemotherapy (C+) and 24 patients (C−) did not. The C+ group had 77 pT1a and 118 pT1c cases, and the C− group included 18 pT1a and 6 pT1c tumors (P Conclusions: Although the present study was a limited retrospective investigation, it suggested that adjuvant chemotherapy had little impact on the survival of stage I CCC patients. Further strategy, such as a molecular targeting agent, is needed to improve survival of CCC, especially in cases with positive peritoneal washing.