Severe genitourinary toxicity following radiation therapy for prostate cancer - How long does it last?

Purpose: Radiation therapy is a common treatment for localized prostate cancer but long-term data are sparse on treatment related toxicity compared to observation. We evaluated the time course of grade 2-4 genitourinary toxicities in men treated with primary radiation or observation for T1-T2 prostate cancer. Materials and Methods: We performed a population based cohort study using Medicare claims data linked to SEER (Surveillance, Epidemiology and End Results) data. Cumulative incidence functions for time to first genitourinary event were calculated based on the competing risks model with death before any genitourinary event as a competing event. The generalized estimating equation method was used to evaluate the risk ratios of recurrent events. Results: Of the study patients 60,134 received radiation therapy and 25,904 underwent observation. The adjusted risk ratio for genitourinary toxicity was 2.49 (95% CI 2.00-3.11) for 10 years and thereafter. Patients who had required prior procedures for obstruction/stricture, including transurethral prostate resection, before radiation therapy were at significantly increased risk for genitourinary toxicity (risk ratio 2.78, 95% CI 2.56-2.94). Conclusions: This study demonstrates that the increased risk of grade 2-4 genitourinary toxicities attributable to radiation therapy persists 10 years after treatment and thereafter. Patients who required prior procedures for obstruction/stricture were at higher risk for genitourinary toxicity than those without these preexisting conditions.