Prediction of alpha-blocker response in men with benign prostatic hyperplasia by magnetic resonance imaging.

Objectives: To assess the value of magnetic resonance imaging (MRI) for predicting the alpha-blocker response in men with symptomatic benign prostatic hyperplasia (BPH) and to examine the relationship between MRI and the area density of smooth muscle cells in BPH.

Methods: Twenty-eight men were consecutively enrolled in this study and received tamsulosin 0.2 mg once daily for 4 to 6 weeks. The efficacy of tamsulosin was determined by measuring improvements in the maximum urinary flow rate (Qmax) and International Prostate Symptom Score (IPSS). The patients underwent T2-weighted MRI and were separated into a high (H) or iso-low (IL) group according to the signal intensity of the inner gland of the prostate compared with that of bone marrow of the proximal femur head. The area density of smooth muscle cells was determined using immunostaining with antiactin antibody in 16 prostate specimens.

Results: IPSS significantly decreased after the administration of tamsulosin from 16 +/- 1 to 8 +/- 1 (n = 28, P <0.0001 ), and 76.7% of the patients had an improved IPSS of 25% or greater. Qmax was significantly increased in group IL (P = 0.03) but not in group H. Of the patients in group IL, 53.3% had a Qmax response (an increase of Qmax of 30% or more); 15.4% did so in group H (P = 0.04). The area density of smooth muscle cells was 48.1 +/- 3.7% in group IL (n = 9) and 36.7 +/- 3.2% in group H (n = 7, P = 0.04).

Conclusions: MRI is useful in estimating the area density of smooth muscle cells in the prostate and in predicting Qmax response for alpha-blocker therapy in patients with symptomatic BPH.