Does Finasteride Prevent Prostate Cancer?

Journal Watch. 2003;2(7) 

Introduction

Finasteride (Proscar), which inhibits conversion of testosterone to the more potent androgen dihydrotestosterone, reduces symptoms of benign prostatic hyperplasia (BPH). Because androgens promote the development of prostate cancer, a multicenter trial was undertaken to determine whether finasteride prevents prostate cancer.

Researchers randomized more than 18,000 men (age, 55 or older) with normal digital examinations and prostate-specific antigen (PSA) levels of ≤3 ng/mL to receive either finasteride (5 mg daily) or placebo for 7 years. During the trial, prostate biopsies were recommended if digital exams became abnormal or if PSA levels exceeded 4.0 ng/mL (in the finasteride group, PSA values were adjusted to account for finasteride's PSA-lowering effect); biopsies also were recommended for all participants at the end of the study. About half the participants ultimately underwent biopsies.

Among men who underwent biopsies, prostate cancer was diagnosed in 18.4% of finasteride recipients and 24.4% of placebo recipients -- a significant difference. However, high-grade tumors (Gleason score, 7-10) were diagnosed more frequently in the finasteride group than in the placebo group (6.4% vs. 5.1% of participants). Compared with placebo recipients, finasteride recipients experienced fewer urinary symptoms (due to finasteride's effect on BPH) but more sexual dysfunction.

The results of this study are not straightforward: Finasteride was associated with a reduced incidence of prostate cancer but with a greater proportion of cases with high-grade histology. The authors and an editorialist discuss several possible reasons for this finding, none of which is proven. The editorialist concludes, "on balance, finasteride does not seem to be an attractive agent for the chemoprevention of prostate cancer."

-- Allan S. Brett, MD

Thompson IM et al. The influence of finasteride on the development of prostate cancer. N Engl J Med 2003 Jul 17; 349:215-24.

Scardino PT. The prevention of prostate cancer -- The dilemma continues. N Engl J Med 2003 Jul 17; 349:297-9.

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