The efficacy of Stereotactic body radiation therapy and the impact of systemic treatments in oligometastatic patients from prostate cancer

Background: Diagnoses of oligometastatic prostate cancer (PC) increased in the recent years thanks to the advancement in imaging and more effective systemic therapies. Here we evaluate the efficacy of Stereotactic Body Radiation Therapy (SBRT) in oligorecurrent and oligoprogressive PC. Methods: We included patients with a maximum of five metastases diagnosed in a maximum of two target organs. Concomitant treatment with hormonal therapies or chemotherapies was allowed. End points of the present study were the outcome in terms of Local control of treated metastases (LC), out-field progression free survival, overall progression free survival (PFS), and overall survival. Results: We included in the analysis 64 patients treated on 90 metastases. Fifty (78.1%) patients were treated on lymph nodes, 2 (3.1%) patients simultaneously on lymph node and bone while 10 (15.7%) patients on bone only. Lung metastases were treated in 2 (3.1%) patients. Thirty-seven (57.81%) were without androgen deprivation therapy when treated with SBRT. Median follow-up was 15.2 months. Rates of LC at 6-, 12-, and 18- months were 94%, 88%, and 84%, respectively. Oligoprogressive patients compared to oligorecurrent (HR 9.10, P = 0.049) and prolongation of time from diagnosis of metastases to SBRT (HR 1.03, P = 0.047) were associated with worse LC. Median PFS was 6.6 months (range 1.1-42.4). Castration resistant patients experienced worse PFS compared to castration sensitive group (HR 2.12, P = 0.021). Conclusions: Stereotactic body radiation therapy seems to be an effective treatment for metastases from PC. Prospective trials are necessary to better define selection of patients and to evaluate combination of SBRT and new systemic drugs in castration resistant patients.