Efficacy and Safety of Prostate Stereotactic Body Radiotherapy for Metastatic Castration-Resistant Prostate Cancer: A Prospective Cohort Study

Abstract Background The efficacy and safety of prostate SBRT in men with mCRPC is unknown. Materials and methods A prospective cohort study was conducted with 125 men diagnosed with mCRPC. All patients received ADT plus chemotherapy. Patients were randomly assigned to receive daily prostate SBRT (36–48 Gy in 6–8 fractions). Patients who did not receive SBRT served as controls. Results The primary endpoints were PFS and OS. After 89 months of total follow-up, the median PFS was 13.8 months in the SBRT group (n = 61) and 12.0 months in the control group (n = 64) (HR, 0.87; 95% CI, 0.61–1.24; P = 0.249). The OS was 25.7 months in the SBRT group and 23.8 months in the control group (HR, 0.93; 95% CI, 0.65–1.33; P = 0.230). A non-significant increase in the PSA response rate (50.8% vs. 43.7%) and time to PSA progression (8.3 months vs. 7.0 months) was observed in the SBRT group compared to the control group; however, the time to symptomatic progression was significantly prolonged in the SBRT group (11.3 months) compared to the control group (8.5 months) (HR, 0.76; 95% CI, 0.53–1.08; P = 0.019). There was an 11.5% incidence of radiation cystitis and radiation rectitis in the SBRT group, and the degree and incidence of hormone-related and chemotherapy-related adverse events were similar between the two groups. Conclusion Adding prostate SBRT significantly prolonged the time to symptomatic progression and non-significantly prolonged PFS and OS among men with mCRPC compared to treatment with ADT plus chemotherapy alone.