Urinary morbidity after permanent prostate brachytherapy - impact of dose to the urethra vs. sources placed in close vicinity to the urethra.

Abstract

The impact of the dose to the urethra and sources placed close to the urethra on urinary morbidity after permanent prostate brachytherapy (PPB) is not well known. Fifty-nine patients were surveyed prospectively before treatment (A), 1 month after (B) and > 1 year after PPB (C) using a validated questionnaire (Expanded Prostate Cancer Index Composite). Computed tomography (CT) postimplant scans were performed at days 1 (Foley catheter in situ) and 30 after PPB and sources within 5mm of the urethra at day 1 were identified. As opposed to the urethral dose-volume histogram, a larger number of sources within 5mm of the urethra at day 1 predicted significantly larger urinary bother score changes at times B and C - with an impact on incontinence and frequency (e.g. moderate/big problem with leaking urine in 25% vs. 3%, p = 0.02; moderate/big problem with frequent urination in 33% vs. 7%, p < 0.01, at time C with vs. without ≥ 3 sources in a single strand placed close to the urethra). Placement of sources with a minimum distance of a few mm to the urethra should be a major aim to avoid urinary morbidity irrespective of the urethral dose-volume histogram.