LONG-TERM EFFECTS OF FINASTERIDE ON PROSTATE TISSUE COMPOSITION

Objectives. To determine the long-term effects of finasteride treatment on prostate tissue composition; to relate these effects to clinical outcomes; and to test the hypothesis that finasteride exerts a selective or preferential action on the transition zone. Methods. Nineteen men with symptomatic benign prostatic hyperplasia (BPH) who completed a 6-month double-blind trial of finasteride were enrolled in a 24-month open-label extension study of drug responders. Magnetic resonance imaging and prostate biopsy for morphometric analysis were performed together 70 times: at baseline (n 5 19), after treatment periods of intermediate duration (6 to 18 months, n 5 32), and after long-term drug treatment (24 to 30 months, n 5 19). At baseline, prostate volume averaged 51 cc, of which 57 % was transition zone. Results. Decreases in symptom score, dihydrotestosterone and prostate-specific antigen levels, and pros-tate volume occurred at 6 months (P,0.01), stabilized, and were maintained without further long-term decreases. Prostate epithelium contracted progressively from baseline (19.2 % tissue composition; 6.0-cc volume; 3.2 stroma/epithelial ratio) to intermediate (12.5%, 3.3 cc, and 5.6, respectively) to long-term treatment (6.4%, 2.0 cc, and 17.4, respectively, P,0.01 for all). Percent epithelial contraction was simila