The Timing of Salvage Radiotherapy After Radical Prostatectomy: A Systematic Review

Abstract

Salvage radiotherapy (SRT) after radical prostatectomy can potentially eradicate residual microscopic disease. Defining the optimal patient and treatment factors is essential and is particularly relevant within the context of adjuvant vs early vs delayed postoperative radiotherapy (RT). A systematic review of all published SRT studies was performed to identify the pathologic, clinical, and treatment factors associated with relapse-free survival (RFS) after SRT. A total of 41 studies encompassing 5597 patients satisfied the study entry criteria. Radiobiologic interpretation of biochemical tumor control was used to provide the framework for the observed relationships. Prostate-specific antigen (PSA) level before SRT (P<.0001) and RT dose (P=.0052) had a significant and independent association with RFS. There was an average 2.6% loss of RFS for each incremental 0.1 ng/mL PSA at the time of SRT (95% CI, ∼2.2-3.1). With a PSA level of 0.2 ng/mL or less before SRT, the RFS approached 64%. The dose for salvage RT in the range of 60-70 Gy seemed to be on the steep part of the sigmoidal dose-response curve, with a dose of 70 Gy achieving 54% RFS compared with only 34% for 60 Gy. There was a 2% improvement in RFS for each additional Gy (95% CI, ∼0.9-3.2). The observed dose-response was less robust on sensitivity analysis. This study provides Level 2a evidence for initiating SRT at the lowest possible PSA. Dose escalation is also suggested by the data. Progressively better tumor control rates with SRT after radical prostatectomy are achieved with a lower PSA at initiation and with a higher RT dose. Early salvage RT may be an equivalent strategy to adjuvant RT.