Initially, the trial randomly assigned more than 18,000 men to receive either finasteride or a placebo. After seven years, the study compared rates of prostate cancer in the two groups. While men in the finasteride group were 25% less likely overall to have prostate cancer, they were also paradoxically more likely to have high-grade prostate cancer. Ultimately, these results led to recommendations against using the drug for the prevention of prostate cancer.
In January of this year, PCPT investigators reported data after 18 years of follow up in a letter to the editor of The New England Journal of Medicine. Their statistical analysis found that prostate cancer-specific mortality between patients in the finasteride and placebo groups were comparable (.43% vs. .60%, respectively). The results were surprising due to the earlier results that showed a higher risk for highgrade prostate cancer, which tends to grow more aggressively and can be more difficult to treat.
Finasteride is a 5-alphareductase inhibitor,
a hormone blocking drug, that is prescribed for enlarged prostate (benign prostatic hyperplasia, or BPH) and male pattern baldness. Trade names include Proscar and Propecia. Finasteride works by blocking the body's production of a male hormone called dihydrotestosterone. Finasteride may help control conditions of baldness and BPH, but it will not cure them. If men discontinue treatment, the conditions will return.
A similar drug is dutasteride, trade name Avodart, that also has been shown in clinical trials to be associated with significantly more high-grade prostate cancer.
Dr. Catalona commented, "All of these men had no evidence of prostate cancer when they were enrolled in the trial, and virtually all either underwent prostate biopsy during the trial because of screening test results or as part of the trial protocol socalled 'end of study' biopsies. Thus, most of the cancers detected were treated very early, likely a key reason for the low prostate cancer mortality rates observed in the study - approximately one-half percent. As such, these results might not be generalizable to men in other circumstances."
Side effects still a serious concern
Other discussions in the medical community concern finasteride's potential adverse side effects. In addition to the greater risk of highgrade prostate cancer, the FDA label for 5-alpha-reductase inhibitors include a warning of potential adverse sexual events and depression. Several studies have assessed these risks in patients taking finasteride, which can have a significant and persistent impact on mental and sexual health.
The U.S. National Institutes of Health also recognizes Post-Finasteride Syndrome (PFS), which describes persistent sexual, neurological, and physical adverse reactions in patients who have taken finasteride. Visit the Post-Finasteride Syndrome Foundation website to learn more www.pfsfoundation.org.
In addition, previous QUEST articles have reported on the research assessing these side effects. Visit www.drcatalona.com and search "finasteride" for more detailed coverage of these issues.