The effect of adjuvant radiation on survival in early stage clear cell ovarian carcinoma.

OBJECTIVE:To assess the impact of adjuvant radiotherapy (RT) on survival in patients with stage I and II ovarian clear cell carcinoma (OCCC). METHODS:Data collection and analysis of stage I and II OCCC patients treated at two tertiary centers in Toronto, between 1995 and 2014, was performed. Descriptive statistics and Kaplan-Meier survival probability estimates were completed. The log-rank test was used to compare survival curves. RESULTS:163 patients were eligible. 44 (27%) patients were treated with adjuvant RT: 37 of them received adjuvant chemotherapy (CT), and 7 had RT only. In the no-RT group, there were 119 patients: 83 patients received adjuvant CT and 36 had no adjuvant treatment. The 10year progression free survival (PFS) was 65% for patients treated with RT, and 59% no-RT patients. There were a total of 41 (25%) recurrences in the cohort: 12 (27.2%) patients in RT group and 29 (24.3%) in the no-RT group. On multivariable analysis, adjuvant RT was not significantly associated with an increased PFS (0.85 (0.44-1.63) p=0.63) or overall survival (OS) (0.84 (0.39-1.82) p=0.66). In the subset of 59 patients defined as high-risk: stage IC with positive cytology and/or surface involvement and stage II: RT was not found to be associated with a better PFS (HR 1.18 (95% CI: 0.55-2.54) or O S(HR 1.04 (95% CI: 0.40-2.69)). CONCLUSION:Adjuvant RT was not found to be associated with a survival benefit in patients with stage I and II ovarian clear cell carcinoma or in a high risk subset of patients including stage IC cytology positive/surface involvement and stage II patients.