Objective This study aimed to report clinical outcomes of salvage radiotherapy for recurrent ovarian cancer and identify predictors of clinical outcomes.

Methods We retrospectively reviewed data of patients who received salvage radiotherapy for recurrent ovarian cancer between January 2011 and June 2021. Stereotactic body radiotherapy, involved-field radiotherapy with conventional fractionation, and non-involved-field radiotherapy with conventional fractionation were included in this study. Local failure-free survival, progression-free survival, chemotherapy-free survival, and overall survival were assessed. Additionally, potential prognostic factors for survival were analyzed.

Results A total of 79 patients were included with 114 recurrent lesions. The median follow-up was 18.3 months (range 1.7–83). The 2-year local failure-free survival, progression-free survival, chemotherapy-free survival, and overall survival rates were 80.7%, 10.6%, 21.2%, and 74.7%, respectively. Pre-radiotherapy platinum resistance (hazard ratio (HR) 3.326, p<0.001) and short pre-radiotherapy CA-125 doubling time (HR 3.664, p<0.001) were associated with poor chemotherapy-free survival. The 1-year chemotherapy-free survival rates of patients with both risk factors, a single risk factor, and no risk factor were 0%, 20.4%, and 53.5%, respectively. The difference between risk groups was statistically significant: low risk versus intermediate risk (p<0.001) and intermediate risk versus high risk (p<0.001).

Conclusions Salvage radiotherapy for recurrent ovarian cancer resulted in local control with improved chemotherapy-free survival in carefully selected patients. Our results suggest that the consideration of pre-radiotherapy platinum resistance and pre-radiotherapy CA-125 doubling time could help with patient selection.