Predictors for Chronic Urinary Toxicity After the Treatment of Prostate Cancer With Adaptive Three-Dimensional Conformal Radiotherapy: Dose–Volume Analysis of a Phase II Dose-Escalation Study

To identify factors predictive for chronic urinary toxicity secondary to high-dose adaptive three-dimensional conformal radiation.From 1999 to 2002, 331 consecutive patients with clinical Stage II-III prostate cancer were prospectively treated (median dose, 75.6 Gy). The bladder was contoured, and the bladder wall was defined as the outer 3 mm of the bladder solid volume. Toxicity was quantified according to the National Cancer Institute Common Toxicity Criteria 2.0. Median follow-up was 1.6 years.The 3-year rates of Gradeor =2 and Grade 3 chronic urinary toxicity were 17.0% and 3.6%, respectively. Prostate volume, confidence-limited patient-specific planning target volume, bladder wall volume, and acute urinary toxicity were all found to be accurate predictors for chronic urinary toxicity. The volume of bladder wall receivingor =30 Gy (V30) andor =82 Gy (V82), along with prostate volume, were all clinically useful predictors of Gradeor =2 and Grade 3 chronic urinary toxicity and chronic urinary retention. Both Gradeor =2 (p = 0.001) and Grade 3 (p = 0.03) acute urinary toxicity were predictive for the development of Gradeor =2 (p = 0.001, p = 0.03) and Grade 3 (p = 0.05, p0.001) chronic urinary toxicity. On Cox multivariate analysis the development of acute toxicity was independently predictive for the development of both Gradeor =2 and Grade 3 chronic urinary toxicity.Acute urinary toxicity and bladder wall dose-volume endpoints are strong predictors for the development of subsequent chronic urinary toxicity. Our recommendation is to attempt to limit the bladder wall V30 to30 cm(3) and the V82 to7 cm(3) when possible. If bladder wall information is not available, bladder solid V30 and V82 may be used.