(Objective) Enlarged prostate often causes pubic arch interference during needle insertion on transperineal interstitial permanent prostate brachytherapy. Pre-treatment hormonal therapy is necessary for downsizing the prostate gland in such cases. The degree of prostate downsizing with antiandrogen treatment before iodine 125 permanent seed implant brachytherapy and its relation to clinical as well as pathological parameters were assessed. (Methods) From September 2003 to March 2005, 110 patients underwent permanent seed implantation and 86 patients of all received antiandrogen depriviation prior to the treatment at our institute. Prostate volume was measured using transrectal ultrasound at the time of cancer diagnosis and before the seed implant. Correlations between prostate downsizing and clinical as well as pathological parameters were evaluated. (Results) Mean percent volume of the prostate after the size reduction with average of 6.0 months antiandrogen monotherapy, 7.7 months LHRH agoniost and 8.2 months maximum androgen blockage (MAB) was 83%, 63%, and 60%, respectively. Mann-Whitney U test revealed that the degree of prostate downsizing is significantly correlated with the prostate volume in patients with prostate cancer utilizing LHRH agonists. (Conclusions) Antiandrogen monotherapy can be an alternative for prostate downsizing before interstitial brachytherapy. Utilizing LHRH agonists or MAB is recommended for cases with larger gland volume.
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