Treatment with finasteride for seven years reduced the incidence of prostate cancer by approximately 25% without increasing the incidence of aggressive prostate cancers. These findings, which included a reanalysis of previously reported results, were published in Cancer Prevention Research. 

Finasteride (marketed as Proscar, Propecia, Fincar, Finpecia, Finax, Finast, Finara, Finalo, Prosteride, Gefina, Finasterid IVAX, and Finasterid Alternova) is a drug that has been approved by the FDA for the treatment of benign hypertrophy of the prostate and is also marketed in some countries for treatment of male pattern baldness. Finasteride works by inhibiting the conversion of the male hormone testosterone to the potent androgen dihydrotestosterone; in doing so, finasteride reduces the size of the prostate. The main side effects of finasteride are reduced volume of ejaculate, erectile dysfunction, loss of libido, and enlargement of the breasts in males.

Researchers affiliated with the Finastride Prostate Prevention Trial recently conducted a reanalysis of the original large trial, in which 18,882 men over the age of 55 years were treated either with finasteride or placebo (inactive substitute) for seven years or until they developed prostate cancer. Planned biopsies (removal of a sample of tissue for laboratory evaluation) were performed at the end of seven years. In the original analysis, prostate cancer was detected in 19.4% of the patients in the finasteride group compared with 24% in the placebo group. However, 6% of the prostate cancers in the finasteride group were considered to be aggressive, compared with 5% in the placebo group. This led researchers to believe that finasteride may actually increase the risk of aggressive prostate cancers among users.

The researchers recently conducted four updated analyses from the trial with a longer follow-up to further explore the relationship between finasteride and prostate cancer.

• Overall, patients treated with finasteride did not have a higher incidence of aggressive prostate cancers compared with those who received placebo.
• Men who were treated with finasteride had an approximate 25% lower risk of developing prostate cancer than those who received placebo.
• Treatment with finasteride for seven years remained safe and generally well-tolerated.

The researchers concluded that the long-term use of finasteride appears to be an appropriate way in which to reduce the risk of prostate cancer among men who are at a high risk of developing the disease.  Men who are at a high risk of developing prostate cancer may wish to speak with their physician regarding their individual risks and benefits of participation in a clinical trial further evaluating finasteride or other novel approaches to reduce the risk of developing prostate cancer. Two sources of information regarding ongoing clinical trials include the National Cancer Institute (www.cancer.gov) and www.eCancerTrials.com.

References:

1. Thompson IM, Goodman PJ, Tangen CM, et al. The influence of finasteride on the development of prostate cancer. New England Journal of Medicine. 2003;349:213-222.
2. Redman MW, Tangen CM, Goodman PJ, et al. Finasteride does not increase the risk of high-grade prostate prostate cancer: A bias-adjusted modeling approach. Cancer Prevention Research [online publication]. May 18, 2208. 10.1158/1940-6207.CAPR-08-0092.
3. Pinsky P, Parnes H, and Ford L. Estimating rates of true high-grade disease in the prostate prevention trial. Cancer Prevention Research [online publication]. May 18, 2008. 10.1158/1940-6207.CAPR-07-0007. 
4. Lucia MS, Darke AK, Goodman PJ, et al. Pathologic characteristics of cancers detected in the prostate prevention trial: Implications for prostate cancer detection and prevention. Cancer Prevention Research [online publication]. May 18, 2008. 10.1158/1940-6207.CAPR-08-0078.
5. Logothetis CJ and Schellhammer PF. High-grade prostate cancer and the Cancer Prevention Trial. Cancer Prevention Research [online publication]. May 18, 2008.10.1158/1940-6207.CAPR-08-0085.

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