Background:The aim of the present study is to evaluate the impact of metastases-directed stereotactic body radiotherapy in two groups of oligometastatic prostate cancer (PC) patients: oligorecurrent PC and oligoprogressive castration-resistant PC (oligo-CRPC).Methods:Inclusion criteria of the present multicentre retrospective analysis were: (1) oligorecurrent PC, defined as the presence of 1–3 lesions (bone or nodes) detected with choline positron emission tomography or CT plus bone scan following biochemical recurrence; (2) oligo-CRPC, defined as metastases (bone or nodes) detected after a prostatic-specific antigen rise during androgen deprivation therapy (ADT). Primary end points were: distant progression-free survival (DPFS) and ADT-free survival in oligorecurrent PC patients; DPFS and second-line systemic treatment-free survival in oligo-CRPC patients.Results:About 100 patients with oligorecurrent PC (139 lesions) and 41 with oligo-CRPC (70 lesions), treated between March 2010 and April 2016, were analysed. After a median follow-up of 20.4 months, in the oligorecurrent group 1- and 2-year DPFS were 64.4 and 43%. The rate of LC was 92.8% at 2 years. At a median follow-up of 23.4 months, in the oligo-CRPC group 1- and 2-year DPFS were 43.2 and 21.6%. Limitations include the retrospective design.Conclusions:Stereotactic body radiotherapy seems to be a useful treatment both for oligorecurrent and oligo-CRPC.

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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.

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