Urethral strictures following high-dose-rate brachytherapy for prostate cancer: Analysis of risk factors

PURPOSE: High-dose-rate brachytherapy is an established technique to deliver a conformal dose of radiation to patients with prostate cancer. The William Buckland Radiotherapy Center has been performing high-dose-rate brachytherapy with external beam radiation treatment for prostate cancer since 1998 and has an extensive prospective database on all patients treated. The purpose of this analysis was to assess the risk of stricture formation and identify the predictive or causative factors. METHODS AND MATERIALS: Three hundred fifty-four patients were treated between 1998 and 2008. Patients received one of three differing dose schedules: 20 Gy in four treatments (20 Gy/4), 18 Gy/3, and 19 Gy/2 during three sequential time periods. Nelson-Aalen cumulative hazard modeling was used to estimate risk of events over time. Potential risk factors, including dose, were identified and used in the analysis. RESULTS: There were 45 patients who developed at least one stricture, an overall risk of 8.2% at 2 years. The 2-year risk of stricture formation was 3.4%, 2.3%, and 31.6% for 18 Gy/3, 20 Gy/4, and 19 Gy/2, respectively. Most strictures occurred in the bulbomembranous urethra (50%) or external sphincter region (33%). On multivariable analysis, the dose schedule used was the only significant predictor for increased stricture formation. CONCLUSIONS: In our patients, those who received 19 Gy/2 were at a significantly higher risk of stricture formation. Most of these, strictures were mild, requiring only one intervention but a 2-year stricture risk of 31.6% was striking, and we have modified our protocol. (C) 2013 American Brachytherapy Society. Published by Elsevier Inc. All rights reserved.