Radiotherapy after radical prostatectomy: Effect of timing of postprostatectomy radiation on functional outcomes

Introduction and objective: The timing of radiotherapy (RT) after prostatectomy is controversial, and its effect on sexual, urinary, and bowel function is unknown. This study seeks to compare patient-reported functional outcomes after radical prostatectomy (RP) and postprostatectomy radiation as well as elucidate the timing of radiation to allow optimal recovery of function. Methods: The Comparative Effectiveness Analysis of Surgery and Radiation (CEASAR) study is a prospective, population-based, observational study of men with localized prostate cancer. Patient-reported sexual, urinary, and bowel functional outcomes were measured using the 26-item Expanded Prostate Index Composite at baseline and at 6, 12, 36, and 60 months after enrollment. Functional outcomes were compared among men undergoing RP alone, post-RP adjuvant radiation (RP + aRT), and post-RP salvage radiation (RP + sRT) using multivariable models controlling for baseline clinical, demographic, and functional characteristics. Results: Among 1,482 CEASAR participants initially treated with RP for clinically localized prostate cancer, 11.5% (N = 170) received adjuvant (aRT, N = 57) or salvage (sRT, N = 113) radiation. Men who received post-RP RT had worse scores in all domains (sexual function [−9.0, 95% confidence interval {−14.5, −3.6}, P < 0.001], incontinence [−8.8, {−14.0, −3.6}, P < 0.001], irritative voiding [−5.9, {−9.0, −2.8}, P < 0.001], bowel irritative [−3.5, {-5.8, −1.2}, P = 0.002], and hormonal function [−4.5, {−7.2, −1.7}, P = 0.001]) compared to RP alone at 5 years of follow-up. Compared to men treated with RP alone in an adjusted linear model, sRT was associated with significantly worse scores in all functional domains. aRT was associated with significantly worse incontinence, urinary irritation, and hormonal function domain scores compared to RP alone at 5 years of follow-up. On multivariable modeling, RT administered approximately 24 months after RP was associated with the smallest decline in sexual domain score, with an adjusted mean decrease of 8.85 points (95% confidence interval [−19.8, 2.1]) from post-RP, pre-RT baseline. Conclusions: In men with localized prostate cancer, post-RP RT was associated with significantly worse sexual, urinary, and bowel function domain scores at 5 years compared to RP alone. Radiation delayed for approximately 24 months after RP may be optimal for preserving erectile function compared to radiation administered closer to the time of RP.