Background. Recent studies have reported improvement of outcomes (progression‐free survival, overall survival, and prolongation of androgen deprivation treatment‐free survival) with stereotactic body radiotherapy (SBRT) in non‐small cell lung cancer and prostate cancer. The aim of this retrospective, multicenter study (MITO RT‐01) was to define activity and safety of SBRT in a very large, real‐world data set of patients with metastatic, persistent, and recurrent ovarian cancer (MPR‐OC). Materials and 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 endpoints were acute and late toxicities and the 24‐month actuarial late toxicity‐free survival. Objective response rate (ORR) included CR and partial response (PR). Clinical benefit (CB) included ORR and stable disease (SD). Toxicity was evaluated by the Radiation Therapy Oncology Group (RTOG) and the European Organization for Research and Treatment of Cancer (EORTC) and Common Terminology Criteria for Adverse Events (CTCAE) 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, giving a rate of CB of 96.4%. Patient aged ≤60 years, planning target volume (PTV) ≤18 cm³, lymph node disease, and biologically effective dose α/β10 > 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; of 63 side effects, 48 were grade 1, and 15 were grade 2. The 24‐month late toxicity‐free survival rate was 95.1%. Conclusions. This study confirms the activity and safety of SBRT in patients with MPR‐OC and identifies clinical and treatment parameters able to predict CR and LC rate. Implications for Practice. This study aimed to define activity and safety of stereotactic body radiotherapy (SBRT) in a very large, real life data set of patients with metastatic, persistent, recurrent ovarian cancer (MPR‐OC). Patient age <60 years, PTV 70 Gy were associated with higher chance of complete response (CR). Achievement of CR and total dose >25 Gy were associated with better local control (LC) rate. Mild toxicity was experienced in 20.7% of patients. In conclusion, 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.

PET/CT is a valuable tool to detect lymph node (LN) metastases in patients with biochemical failure after primary treatment for prostate cancer (PCa). The aim was to assess the predictive role of imaging parameters derived by ¹¹C-choline PET/CT on survival outcomes—overall survival, locoregional relapse-free survival, clinical relapse-free survival (cRFS), and biochemical relapse-free survival (bRFS)—in patients treated with helical tomotherapy (HTT) for LN recurrence. Methods: This retrospective study included 68 patients affected by PCa (mean age, 68 y; age range, 51–81 y) with biochemical recurrence after primary treatment (median prostate-specific antigen values obtained at the time of PET/CT scan, 2.42 ng/mL; range, 0.61–27.56 ng/mL) who underwent ¹¹C-choline PET/CT from January 2005 to January 2013 and were treated with HTT in correspondence of the pathologic choline LN uptake. PET-derived parameters, including maximum/mean standardized uptake value (SUV_max and SUV_mean, respectively) and metabolic tumor volume (MTV) with a threshold of 40%, 50%, and 60% were calculated. The best cutoff values of PET-derived parameters discriminating between patients with and without relapse, after treatment guided by PET, were assessed by receiver-operating-characteristic (ROC) curve analysis. Univariate and multivariate Cox regression analysis including the most predictive PET-derived parameters and survival outcomes were performed. Results: The median follow-up was 20 mo (mean, 26 mo; range, 3–97 mo). ¹¹C-choline PET/CT showed pathologic LN uptake in 4 patients at the pelvic level, in 5 at the abdominal level, in 13 at both the pelvic and the abdominal level, and in 46 at the abdominal or pelvic or other sites. The 2-y overall survival, locoregional relapse-free survival, cRFS, and bRFS were 87%, 91%, 51%, and 40%, respectively. On the basis of ROC curves, the most discriminative cutoff value for MTV values was an MTV threshold of 60% (MTV60) of greater than 0.64 cm³. No significant cutoff values were found for SUV_max or SUV_mean at univariate analysis, whereas MTV60 was confirmed as an independent predictor in multivariate analysis and significantly correlated with bRFS and cRFS. MTV60 and extrapelvic disease well predict the risk of cRFS. Conclusion: ¹¹C-choline PET/CT performed as a guide for HTT on LN recurrence is predictive of survival. In particular, MTV60 and extrapelvic disease were the best predictors of tumor response for bRFS and cRFS in PCa patients with LN recurrence after primary treatment. This information may be useful in emerging treatment strategies.