Correlation between prostate brachytherapy-related urethral stricture and peri-apical urethral dosimetry: a matched case-control study.

BACKGROUND AND PURPOSE: Radiation dose to the bulbomembranous urethra has been shown to correlate with urethral stricture formation. This retrospective case-control study was designed to explore the relationship between dose to the apical/peri-apical regions of the urethra and development of brachytherapy (BXT)-related urethral stricture.

MATERIALS AND METHODS: Cases were patients who developed urethral stricture after treatment with BXT as monotherapy and who had urethral dosimetry post-implant. Each case was matched with a control that had not developed urethral stricture. Dosimetry was compared between cases and controls.

RESULTS: Twenty-three cases were pair matched with 23 controls. There were no significant differences between the two groups in terms of age, presenting Prostate Specific Antigen (PSA), International Prostate Symptom Score (IPSS) or Gleason score. The dose delivered to the peri-apical and apical urethra was significantly higher for cases when compared with controls (peri-apical urethra: mean V(150) 1.1 Vs 0.8 cc [p=0.02]; apical urethra: mean dose 200 Vs 174 Gy [p=0.01]). The distance from the prostate apex to isodose lines was also found to be significant in predicting stricture formation.

CONCLUSION: There was evidence to suggest that the development of BXT-related stricture was associated with radiation dose at the apical and peri-apical urethra. Attention to the dose delivered to those areas may minimise the risk of developing such morbidity.