Salvage Radiation Therapy for Biochemical Failure Following Radical Prostatectomy

Background: Radiotherapy to the prostate bed is used to eradicate residual microscopic disease following radical prostatectomy for prostate cancer. Recommendations are based on historical series. Objectives: To determine outcomes and toxicity of contemporary salvage radiation therapy (SRT) to the prostate bed. Methods: We reviewed a prospective ethics committee approved-database of 229 patients referred for SRT. Median pre-radiation prostate-specific antigen (PSA) was 0.5 ng/ml and median follow-up was 50.4 months (range 13.7-128). Treatment was planned and delivered using modern three-dimensional radiation techniques. Mean bioequivalent dose was 71 Gy (range 64-83 Gy). Progression was defined as two consecutive increases in PSA level > 0.2 ng/ml, metastases on follow-up imaging, commencement of anti-androgen treatment for any reason, or death from prostate cancer. Kaplan-Meier survival estimates and multivariate analysis were performed using STATA. Results: Five year progression-free survival was 68% (95% CI 59.8-74.8%), and stratified by PSA the rates were 87%, 70% and 47% for PSA < 0.3, 0.3-0.7 and > 0.7 ng/ml (P < 0.001). Metastasis free survival was 92.5%, prostate cancer-specific survival 96.4%, and overall survival 94.9%. Low pre-radiation PSA value was the most important predictor of progression-free survival (HR 2.76, P < 0.001). Daily image guidance was associated with reduced risk of gastrointestinal and genitourinary toxicity (P < 0.005). Conclusions: Contemporary SRT is associated with favorable outcomes. Early initiation of SRT at PSA < 0.3 ng/ml improves progression-free survival. Daily image guidance with online correction is associated with a decreased incidence of late toxicity.