In 2003, the National Cancer Institute published the results from the Prostate Cancer Prevention Trial (PCPT), a randomized trial to assess the efficacy of finasteride (brand named Proscar), a 5-alpha reductase inhibitor that prevents the conversion of testosterone to dihydrotestosterone and is used for the treatment and shrinkage of benign prostatic hypertrophy.
This trial randomized over 18,000 men to finasteride or placebo and found that finasteride reduced the overall incidence of prostate cancer by nearly 25 percent, but was associated with a 25.5% increase in the number of high-grade cancers, which are often aggressive.
It was not known whether the drug caused more high-grade prostate cancers or merely facilitated their detection. However, as a consequence of this finding, the drug has never become a popular preventive agent for prostate cancer.
Two new studies just published in the Journal of the National Cancer Institute now suggest that finasteride is merely facilitating the detection of the high-grade tumors but not actually increasing their incidence.
In the first study, Dr. Yael Cohen of Gamida Cell in Jerusalem and colleagues determined that finasteride reduces the volume of the prostate and thereby increases the likelihood of finding high-grade cancer cells in a biopsy. They concluded that finasteride accelerates the detection of high-grade cancer, but may not promote its development.
The second study analyzed prostatectomies from the PCPT and found that the relative increase in high-grade tumors in the finasteride group was less than originally believed. The findings further suggest that enhanced detection contributed to the increase in high-grade disease in the finasteride group, reported a team led by Dr. M. Scott Lucia of the University of Colorado Health Sciences Center.
For now, these studies should encourage those who are pursuing the chemopreventive potential of 5-alpha reductase inhibitors, and particularly the benefits of finasteride.
