Transition zone volume and transition zone ratio: predictor of uroflow response to finasteride therapy in benign prostatic hyperplasia patients

Objectives. The aim of this study was to: (1) determine effects of finasteride on transition zone (TZ) volume, TZ ratio (TZ volume/total prostate volume), and total prostate volume; (2) analyze differences in TZ and total volume reduction among patients who improve peak urinary flow rates following finasteride therapy with those who do not; (3) investigate which parameters correlate with improvement in peak urinary flow rate and urinary symptom score; and (4) establish if there is any predictive value of these parameters for response to therapy. Methods. Twenty-three patients with symptomatic benign prostatic hyperplasia (BPH) were treated with finasteride (5 mg/d) for 12 months and underwent transrectal ultrasound (TRUS) evaluation of total and TZ volume of prostate and measurement of peak flow rate and modified Boyarsky symptom score at baseline and at 12 months. Statistical analysis was done by unpaired t, Mann-Whitney, and Spearman rank correlation tests among responders (more than 3 cc/s improvement in peak flow rate) and nonresponders (less than 3 cc/s improvement in peak flow rate) to therapy. Results. (1) Responders had substantial reduction in TZ volume (44.8% versus 16.05%; P < 0.03) and TZ ratio (25% versus 5% increase, P < 0.02) compared with non-responders. (2) There was a significant correlation between reduction in TZ volume (r = 0.50; P < 0.03) and TZ ratio (r = 0.60; P < 0.006) with improvement in peak flow rates. No similar correlation was seen with total prostate volume changes. (3) Pretreatment TZ ratio helped in predicting peak flow improvement following finasteride therapy (r = 0.52; P < 0.01) and there was a 2.5-fold increased chance of improvement if baseline TZ ratio was more than 0.51. The modified Boyarsky symptom score decreased by 3.1 (mean), but there was no correlation with changes in peak urinary flow rate, total prostate volume, TZ volume, and TZ ratio. TZ ratio did not have significant predictive value for improvement in symptom score. Conclusions. This study provides data that simple measurable parameters are available which may be used prior to therapy to predict uroflow response to finasteride and similar agents.