Benefits from Finasteride Chemoprevention
Harms from Finasteride Chemoprevention
Benefits and Harms of Other Prevention Interventions

Note: Separate PDQ summaries on Screening for Prostate Cancer, Prostate Cancer Treatment, and Levels of Evidence for Cancer Screening and Prevention Studies are also available.

Based on good evidence, chemoprevention with finasteride reduces the incidence of prostate cancer, but the evidence is insufficient to determine whether chemoprevention with finasteride reduces mortality from prostate cancer. One large randomized controlled trial (RCT) showed that finasteride, given to men who have not had prostate cancer, reduces the risk of developing this disease. Slightly fewer men in the finasteride group had urinary urgency and urinary frequency; however, the incidence of higher-grade prostate cancer increased in the finasteride group. The clinical significance of histologic grade in men taking finasteride is uncertain.

Levels of Evidence

A. Study Design (Level of Evidence 1)

1: Evidence obtained from randomized controlled trials.

B. Internal Validity: Good for the outcome of incidence, poor for the outcome of mortality.

C. Consistency: Not applicable.

D. Direction and Magnitude of Effect: Absolute reduction in incidence over 7 years was 6% (24.4% with placebo and 18.4% with finasteride); relative risk reduction for incidence was 24.8% (95% confidence interval (CI) 18.6% to 30.6%). There was no difference in the number of men dying from prostate cancer in the 2 groups, although the number of deaths was small.

E. External Validity: Fair, because of small numbers of African American and Hispanic men.

Men in the finasteride group had statistically significantly more erectile dysfunction, loss of libido, and gynecomastia than men in the placebo group.

Levels of Evidence

A. Study Design (Level of Evidence 1)

1: Evidence obtained from randomized controlled trials.

B. Internal Validity: Fair. An RCT of finasteride for the prevention of prostate cancer used an interview (rather than a patient-completed questionnaire) to examine erectile dysfunction and libido during treatment (rather than both before and during treatment).

C. Consistency: Good (evidence other than the RCT supports these effects).

D. Direction and 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% versus 47.3%).
• Erectile dysfunction (67.4% versus 61.5%).
• Loss of libido (65.4% versus 59.6%).
• Gynecomastia (4.5% versus 2.8%).

E. External Validity: Fair, because of small numbers of African American and Hispanic men.

The evidence is insufficient that the prevention strategies of dietary change (i.e., reducing dietary fat or increasing fruits and vegetables), or vitamin E (alpha-tocopherol), selenium, or lycopene supplementation, are effective in reducing prostate cancer incidence or mortality.

Levels of Evidence

A. Study Design for vitamin E and selenium (Level of Evidence 1*)

1: Evidence obtained from randomized controlled trials (*in this case, secondary endpoints from randomized trials).

Study Design for the other interventions (Levels of Evidence 3, 4)

3: Evidence obtained from cohort or case-control studies.

4: Evidence obtained from ecologic and descriptive studies (e.g., international patterns studies, time series).

B. Internal Validity: Fair.

C. Consistency: Poor.

D. Direction and Magnitude of Effect: Uncertain.

E. External Validity: Fair.

Back to Top

Next Section >