A Cochrane review [Abstract] 1 included 13 studies with a total of 34 410 subjects. 3 studies using finasteride lasted 4 years or longer but only one (the Prostate Cancer Prevention Trial, PCPT) was specifically designed to assess the impact of five-alpha-reductase inhibitors (5ARI) on prostate cancer period-prevalence. The mean PSA of enrollees was 2.1 ng/mL. For-cause prostate cancers (prostate cancer clinically detected based on symptoms, an abnormal digital rectal exam, or detected as a result of an abnormal prostate specific antigen value) comprised 54% of all cancers detected. Finasteride was associated with a 26% relative risk reduction in prostate cancers detected for-cause among all randomized subjects (RR 0.74, 95% CI 0.67 to 0.83; absolute risk reduction, ARR = 1.4%; 3.5% versus 4.9%). 6 studies assessed prostate cancers detected overall (for-cause + those detected due to study protocol) with a pooled 26% relative reduction favouring 5ARI (RR 0.74, 95% CI 0.55 to1.00; 2.9% absolute reduction, 6.3% versus 9.2%). Reductions were observed regardless of age, race or family history of prostate cancer but not among men with baseline PSA > 4.0 ng/mL.
A greater number of high Gleason score tumors (7-10 or 8-10) occurred in men on finasteride in the PCPT (Gleason 8-10 tumors identified overall 0.96% in finasteride group versus 0.56% in placebo group; RR 1.70, 95%CI 1.22 to 2.39). Impotence or erectile dysfunction (RR 1.71, 95% CI 1.11 to 2.65) or endocrine effects were more common with finasteride than placebo. There were no differences in overall or prostate cancer mortality between finasteride and placebo in any trial. No trial was designed to assess mortality outcomes though the pooled overall mortality estimates favored placebo statistically nonsignificantly (RR 1.06, 95% CI 0.95 to1.18; 5 studies, n=21539).
Comment: The quality of evidence is downgraded by indirectness (information is inadequate to assess the impact on mortality).
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