Low-Stage Ovarian Clear Cell Carcinoma: Population-Based Outcomes in British Columbia, Canada, With Evidence for a Survival Benefit As a Result of Irradiation

Purpose To evaluate the population-based outcomes of stage I and II ovarian clear cell carcinoma (OCCC) in a North American population treated with carboplatin/paclitaxel and abdominopelvic irradiation. Patients and Methods Retrospective analysis was performed of 241 patients referred in the carboplatin/paclitaxel era. Irradiation was to be used with a few defined exceptions. However, because of differing beliefs as to its effectiveness, its use was consistently avoided by specific oncologists, allowing the opportunity to study its possible effect on disease-free survival (DFS) in these concurrent cohorts. Results Five- and 10-year DFS rates were 84% and 70% for stage IA/B; 67% and 57% for stage IC; and 49% and 44% for stage II, respectively. Five- and 10-year DFS rates for those with stage IC disease based purely on rupture were similar to rates for patients with stage IA/B, at 92% and 71%, respectively. The remaining patients with stage IC had 48% 5- and 10-year DFS. Multivariate analysis using a decision tree identified positive cytology as the most important factor (72% relapse rate if positive and 27% if negative or unknown). If, in addition, the capsule surface was involved, then the relapse rate was 93%. Irradiation had no discernible survival benefit for patients with stage IA and IC (rupture alone), whereas for the remainder of patients with stage IC and stage II, it improved DFS by 20% at 5 years (relative risk, 0.5); the benefit was most evident in the cytologically negative/unknown group. Conclusion DFS is similar in this North American population with early OCCC to the DFS reported in Asia. A potential benefit from irradiation was evident in a subset.