Metastasis-directed stereotactic radiotherapy for oligoprogressive castration-resistant prostate cancer: a multicenter study

PURPOSE: Herein, we report the clinical outcomes of a multicenter study evaluating the role of SBRT in a cohort of patients affected by oligoprogressive castration-resistant prostate cancer (CRPC). MATERIALS AND METHODS: This is a retrospective multicenter observational study including eleven centers. Inclusion criteria of the current study were: (a) Karnofsky performance status > 80, (b) histologically proven diagnosis of PC, (c) 1-5 oligoprogressive metastases, defined as progressive disease at bone or nodes levels (detected by means of choline PET/CT or CT plus bone scan) during ADT, (d) serum testosterone level under 50 ng/ml during ADT, (e) controlled primary tumor, (f) patients treated with SBRT with a dose of at least 5 Gy per fraction to a biologically effective dose (BED) of at least 80 Gy using an alpha-to-beta ratio of 3 Gy, (g) at least 6 months of follow-up post-SBRT. RESULTS: Eighty-six patients for a total of 117 lesions were treated with SBRT. The median follow-up was 30.7 months (range 4-91 months). The median new metastasis-free survival after SBRT was 12.3 months (95% CI 5.5-19.1 months). One- and two-year distant progression-free survival was 52.3% and 33.7%, respectively. Twenty-six out of 86 patients underwent a second course of SBRT due to further oligoprogressive disease: This resulted in a median systemic treatment-free survival of 21.8 months (95% CI 17.8-25.8 months). One-year systemic treatment-free survival was 72.1%. CONCLUSION: SBRT appears to be a promising approach in oligoprogressive castration-resistant prostate cancer. Further investigations are warranted.