Predictive factors for acute and late urinary toxicities after permanent prostate brachytherapy.

Abstract

90 Background: To describe the frequency of acute and late Radiation Therapy Oncology Group (RTOG) urinary toxicity associated with predictive factors and International Prostate Symptom Score (IPSS) in consecutive prostate brachytherapy patients. Methods: From January 2004 to April 2011, 466 patients underwent permanent 125I-seed brachytherapy (median follow-up, 48 months). The IPSS and RTOG toxicity data were prospectively collected. The prostate volume, IPSS before and after brachytherapy and postimplant analysis were examined for an association with urinary toxicity which was defined as urinary RTOG toxicity 1 or more. Logistic regression analysis was used to examine the factors associated with urinary toxicities. Results: The rate of RTOG urinary toxicity Grade 1 or more at 1, 6, 12, 24, 36, 48 months was 67%, 40%, 21%, 31%, 27%, 28%, respectively. Grade 2 or more urinary toxicities were less than 1% at an each point. IPSS was highest at 3 months and returned to normal level at 12 months after brachytherpapy. On univariate analysis, patients with larger prostate size, greater baseline IPSS, the higher post V100 (volume of the prostate covered by 100% of the dose), higher post V150 and higher post D90 (dose that 90% of the target volume received) had more acute urinary toxicities 1 month as well as 12 months after brachytherapy. On multivariate analysis, the significant predictors for urinary toxicities were a greater baseline IPSS and post V100 one month as well as 12 months after brachytherapy (shown below). Conclusions: Most urinary symptoms were tolerated and resolved within 12 months after prostate brachytherapy. Acute and late urinary toxicities after brachytherapy were strongly related with baseline IPSS and the post V100.