Note: Separate PDQ summaries on Prostate Cancer Screening, Prostate Cancer Treatment, and Levels of Evidence for Cancer Screening and Prevention Studies are also available.
Benefits From Finasteride and Dutasteride Chemoprevention
Based on solid evidence, chemoprevention with finasteride and dutasteride reduces the incidence of prostate cancer, but the evidence is inadequate to determine whether chemoprevention with finasteride or dutasteride reduces mortality from prostate cancer.
Magnitude of Effect: Absolute reduction in incidence for more than 7 years with finasteride was 6% (24.4% with placebo and 18.4% with finasteride); relative risk reduction (RRR) for incidence was 24.8% (95% confidence interval [CI], 18.6%-30.6%). There was no difference in the number of men dying from prostate cancer in the two groups, though the number of deaths was small.
In the dutasteride trial, absolute risk reduction was 5.1% at 4 years, and RRR was 22.8% (95% CI, 15.2%-29.8%). There was no difference in prostate cancer or overall mortality. The reduction in prostate cancer incidence occurred primarily in Gleason 5 to 6 cancers. The reduction in incidence primarily in less aggressive cancers (i.e., Gleason 5-6) and not in more aggressive cancers (i.e., Gleason 7-10) raises the question of whether this reduction in incidence would lead to any reduction in mortality. This question is presently unanswered.
|Study Design: Two randomized controlled trials; one for finasteride and one for dutasteride.|
|Internal Validity: Good for the outcome of incidence, poor for the outcome of mortality.|
|External Validity: Fair for the finasteride trial, because of small numbers of African American and Hispanic men. In the dutasteride trial, all men were at higher risk, with a prostate-specific antigen (PSA) of 2.5 to 10.0. Thus, these results are generalizable primarily to high-risk men.|
Harms From Finasteride and Dutasteride Chemoprevention
Men in the finasteride group had statistically significantly more erectile dysfunction, loss of libido, and gynecomastia than men in the placebo group. Men in the finasteride group had a statistically significant incidence of high-grade (Gleason sum 8-10) cancers during the study. Whether this was a histological artifact or not is uncertain.
Magnitude of Effect: Statistically significant increases in the following outcomes were observed in the finasteride group (an additional 9% of men in the finasteride group discontinued therapy at least temporarily because of one of these side effects):
|Percentage in finasteride group versus percentage in placebo group:|
|Reduced volume of ejaculate (60.4% vs. 47.3%).|
|Erectile dysfunction (67.4% vs. 61.5%).|
| Loss of libido (65.4% vs. 59.6%).|
| Gynecomastia (4.5% vs. 2.8%).|
Men in the dutasteride group had a higher incidence of decreased libido and erectile dysfunction than men in the placebo group.