Improved Outcomes With Higher Doses for Salvage Radiotherapy After Prostatectomy

Purpose: To evaluate relapse-free survival with higher doses for patients receiving salvage radiotherapy (RT) after radical prostatectomy (RP). Patients and Methods: A total of 122 patients with pathologically negative lymph nodes received salvage RT after RP from 1984 to 2004. Median prostate bed dose was 60 Gy for 38 patients and 70 Gy for 84 patients. Four months of total androgen suppression and whole-pelvic RT were given concurrently to 68 and 72 patients, respectively. The median follow-up was >5 years. Kaplan-Meier and Cox proportional hazards multivariable analyses were performed for all clinical, pathologic, and treatment factors predicting for biochemical relapse-free survival (bRFS). Results: There were 60 biochemical failures after salvage RT, with a median time to failure of 1.2 years. A dose response was observed, with a 5-year bRFS rate of 25% vs. 58% for prostate bed doses of 60 Gy vs. 70 Gy (p < 0.0001). For patients receiving RT alone the 5-year bRFS rate was 17% vs. 55% (p = 0.016), and for those receiving prostate-bed-only RT it was 23% vs. 66% (p = 0.037) for doses of 60 Gy vs. 70 Gy, respectively. On multivariate analysis a prostate bed dose of 70 Gy (p = 0.012, hazard ratio [HR] 0.48 [95% Confidence Interval (CI), 0.27-0.87]), pre-RT prostate-specific antigen value ≤1 ng/mL (p < 0.0001, HR 0.28 [95% CI, 0.16-0.48]), and lack of seminal vesicle involvement (p = 0.009, HR 0.44 [95% CI, 0.26-0.77]) remained independently significant. Conclusions: A clinically significant dose response from 60 Gy to 70 Gy was observed in the setting of salvage RT after prostatectomy. A dose of 70 Gy to the prostate bed is recommended to achieve optimal disease-free survival.