Radiother Oncol. 2008; published online ahead of print

Bulbomembranous (BM) urethral strictures are the most common grade 2 or higher urinary toxicity following high dose rate brachytherapy (HDRB), according to Australian investigators.

The findings, by researchers affiliated with the Peter MacCallum Cancer Centre and University of Melbourne, are based on a study of 474 patients with clinical localized prostate cancer treated with HDRB. At a median follow-up of 41 months, 38 patients (8%) were diagnosed with urethral stricture (a six-year actuarial risk of 12%), the authors reported. Ninety-two percent of the strictures were BM.

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The researchers estimated the overall actuarial rate of grade 2 or higher BM urethral stricture to be 10.8%, with a median time to diagnosis of 22 months. All strictures were initially managed with either dilatation or optical urethrotomy. Seventeen cases (49%) required second-line therapy and three (9%) required third-line therapy. One patient needed open urethroplasty.

Hypertension also was associated with a 2.8 times higher risk of stricture. Men who had a previous transurethral resection of the prostate (TURP) had a 28% increased risk of stricture compared with men who did not have a prior TURP or hypertension. In addition, each 1-Gy increase in radiation dose per fraction was associated with a 33% increased risk of stricture.

“Both clinical and dosimetric factors appear to influence the risk of stricture formation,” the authors concluded.

The investigators stated that most BM urethral strictures are manageable with minimally invasive procedures.