Three major analyses of data from the largest prostate cancer prevention trial ever completed suggest that finasteride (Proscar), a 5-alpha-reductase inhibitor, can help curb the disease – with more benefit to patients than originally thought.
Initial findings of the U.S. National Cancer Institute's Prostate Cancer Prevention Trial (PCPT), involving more than 18,000 men over age 55, were published in 2003 and showed that men on finasteride had a nearly 25 percent lower risk of developing prostate cancer versus men on placebo.
However, there was a worrisome side to the initial findings: Use of finasteride was also linked to an increased risk of developing high-grade prostate cancers, which are thought to be more aggressive.
That led some experts to worry that finasteride – which is currently approved to treat enlarged prostates – was only preventing lower-grade tumors, which might pose little long-term harm to the patient.
However, in May 2008, researchers published three painstaking new analyses of the PCPT in the journal Cancer Prevention Research that may have eased those concerns.
Two of the studies – one led by Dr. Mary Redman of Fred Hutchinson Cancer Research Center and the other by the NCI's Dr. Paul Pinsky – relied on advanced statistical modeling and an examination of hundreds of prostate tissue samples. Use of finasteride was not found to cause an overall increase in high-grade prostate cancer. Instead, use of finasteride was associated with a modest protective effect.
A third study, led by Dr. M. Scott Lucia from the University of Colorado Denver, looked at whether or not finasteride protected against "clinically significant" prostate tumors. Among their findings was evidence that tumor volume and risk of perineural invasion were lower in men who received finasteride. Moreover, the initially reported differences in high-grade disease may have been caused by a detection bias.
"We've now shown that the cancers prevented by finasteride are often clinically significant, the same kind of cancers that lead to surgery," Dr. Ian Thompson, chair of the Department of Urology at the University of Texas Health Center, San Antonio, and senior author of the two analyses, told the NCI Cancer Bulletin in May.
The bottom line, according to experts, is that finasteride may offer real hope as a preventive agent. However, it’s not yet approved by the Food and Drug Administration for prostate cancer prevention.
In their Perspective piece in the same issue of Cancer Prevention Research, Dr. Christopher Logothetis of M.D. Anderson Cancer Center, Houston, and Dr. Paul Schellhammer of Eastern Virginia Medical School, Norfolk, wrote that, "based on the advances reported for finasteride in this issue of the journal, we conclude that the promise of prostate cancer prevention is a reality."
References
