19 A large, multicenter, retrospective study on efficacy and safety of stereotactic body radiotherapy (SBRT) in oligometastatic ovarian cancer (MITO RT1 study)

Objectives The aim of this retrospective, multicenter study (MITO RT-01) was to define activity and safety of Stereotactic Body Radiotherapy (SBRT) in a very large, real life dataset of metastatic/persistent/recurrent ovarian cancer (MPR-OC) patients. Clinical and SBRT parameters have been analyzed in order to identify predictors of outcome. Methods The endpoints of the study were the rate of complete response (CR) to SBRT, and the 24-month actuarial local control (LC) rate on “per lesion” basis. The secondary end-points were acute and late toxicities, and the 24-month actuarial late toxicity free survival. Toxicity was evaluated by RTOG/EORTC and CTC-AE scales, according to center policy. Logistic and Cox regression were used for the uni- and multivariate analysis of factors predicting clinical CR and actuarial outcomes. Results CR, PR and SD were observed in 291 (65.2%), 106 (23.8%), and 33 (7.4%) lesions. Patient age 70 Gy were associated with higher chance of CR in the multivariate analysis. With a median follow-up of 22 months (range: 3–120), the 24-month actuarial LC rate was 81.9%. Achievement of CR and total dose >25 Gy were associated with better LC rate in the multivariate analysis. Mild toxicity was experienced in 54 (20.7%) patients. The 24- month late toxicity free survival rate was 95.1%. Conclusions This study confirms the activity and safety of SBRT in MPR-OC patients and identifies clinical and treatment parameters able to predict CR and LC rate.