Prostate volume predicts outcome of treatment of benign prostatic hyperplasia with finasteride: meta-analysis of randomized clinical trials.

[OBJECTIVES] Six randomized clinical trials have compared at least 1 year of 5 mg finasteride to placebo in the treatment of clinical benign prostatic hyperplasia (BPH). The findings for the 2601 men in these trials provide an opportunity to investigate the heterogeneity of the effects seen in the individual studies and to identify pretreatment predictors of outcomes as expressed by symptoms or peak urinary flow rates.

[METHODS] A formal meta-analysis using an Empirical Bayes approach employed data from all finasteride studies which included the Phase III trials in North America and Internationally, the Prospect, Early Intervention, and SCARP trials, and the Veterans Administration Cooperative Study which compared terazosin, finasteride, and the combination of these two drugs. A pooled analysis was also undertaken on the combined dataset.

[RESULTS] The effect of finasteride treatment on improvements in total symptom severity, frequency score, and peak urinary flow rate was consistent across all six trials and similar among men with similar prostate volumes at baseline. Symptom severity improved by 1.8 points (95% confidence interval [CI], 0.7 to 2.9) in men with prostate volumes less than 20 cc (n = 72), while the improvement was 2.8 points (95% CI, 2.1 to 3.5) for men with volumes greater than 60 cc (n = 272) on the Quasi-IPSS Scale (range 0 to 30). Similarly, improvements in peak urinary flow rate ranged from 0.89 mL/s (95% CI, -0.05 to 1.83) for men with prostate volumes less than 20 cc to 1.84 mL/s (95% CI, 1.37 to 2.30) in men with volumes greater than 60 cc. The difference in the magnitude of improvement between finasteride and placebo becomes significant (that is, no overlap in 95% CI) for men with a baseline prostate volume assessed by either transrectal ultrasonography or magnetic resonance imaging of greater than 40 cc, which encompasses approximately 50% of the entire population. Baseline prostate volume is a key predictor of treatment outcomes: approximately 80% of the variation in the treatment effects noted between studies could be attributed to differences in mean prostate volumes at baseline. Variation in entry criteria results in large differences in baseline symptom severity status, prostate volume, and consequently apparent inconsistencies in the overall outcomes of these trials.

[CONCLUSIONS] This meta-analysis suggests that finasteride is most effective in men with large prostates. Men with small prostates may not be suitable candidates for finasteride therapy for BPH. The need for a careful reevaluation of the definitions and terminology used when discussing urination problems is apparent.