Stereotactic Body Radiotherapy for High-Risk Localized CARcinoma of the Prostate (SHARP) Consortium: Analysis of 344 Prospectively Treated Patients.

ABSTRACT Purpose To explore the efficacy and toxicity of stereotactic body radiotherapy (SBRT) in high risk prostate cancer (HRPCa) in a consortium of seven institutional phase II trials and prospective registries. Methods and materials Individual patient data were pooled for 344 patients with a minimum follow-up of 24 months. Biochemical recurrence-free survival (BCRFS) and distant metastasis-free survival (DMFS) were estimated using a Kaplan-Meier framework. Fine and Gray competing risk and Cox proportional hazards regression models were developed to assess the association between time to BCR and time to distant metastasis and pre-specified variables of interest. Logistic regression models were developed to evaluate associations between acute and late grade ≥2 genitourinary (GU) and gastrointestinal (GI) and the following a priori specified variables: age, dose per fraction, ADT use, and nodal radiotherapy. Results Median follow-up was 49.5 months. Seventy-two percent of patients received ADT, with a median duration of 9 months, and 19% received elective nodal radiotherapy. Estimated four-year BCRFS and DMFS rates were 81.7% (95% CI, 77.2-86.5%) and 89.1% (95% CI, 85.3%-93.1%). The crude incidences of late grade ≥3 genitourinary and gastrointestinal toxicity were 2.3% and 0.9%. Conclusions These data support a favorable toxicity and efficacy profile for SBRT for HRPCa. Further prospective studies are needed to evaluate the optimal dose and target volume in the context of SBRT for HRPCa.