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

Abstract

Background and purpose: 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.

Materials and methods: 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.

Results: 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).

Conclusions: 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.