Dr. Tom Talbot applies a bandage to study participant Christina Powell after she received a smallpox vaccine earlier this year. (photo by Dana Johnson)
New prostate drug reduces cancer rate
More than 300 men from Middle Tennessean and South Central Kentucky participated at Vanderbilt in a national trial of the first drug that has shown a reduction in the rate of prostate cancer — and a higher rate of the cancer than previously believed.
The New England Journal of Medicine reported June 24 that finasteride lowered the chances of men getting prostate cancer by almost 25 percent in the 10-year trial, which was sponsored by the National Cancer Institute. The study was scheduled to end in May 2004 but closed early because differences in both the placebo and medication arm became apparent. However, not all the news was positive.
“There are several extremely important pieces of information that came from this trial,” said Dr. Joseph A. Smith Jr., William L. Bray of Urologic Surgery and chair of the department. “It showed that cancer was detected in 24 percent of participants on placebo, a rate far higher than the expected 6 percent rate in the general population. Secondly, it showed that finasteride decreased the risk of developing prostate cancer by 25 percent. In addition, though, it had the worrisome finding that men on finasteride who did develop cancer had a higher rate of an aggressive type of tumor.”
Prostate cancer is too frequently dismissed as a cancer that men die with and not from, Smith said. “For many men that’s true, but prostate cancer is the second most common cause of cancer death in the country. Researchers at Vanderbilt are working on methods to discriminate better between these two forms of prostate cancer and to decide which men should undergo aggressive treatment, such as surgery.”
Nationwide, almost 19,000 men 55 years and older were enrolled into the study; 312 of them were at Vanderbilt. All were free of chronic health problems and were randomly assigned to take either 5 mg of finasteride or a placebo once daily for seven years, with the participants and the physicians not knowing who received which pill.
A blood test, Prostate-specific antigen (PSA) and rectal exams were repeated annually, and the participants’ prostates were biopsied at the end of their seven-year term. When the study ended, tissue from 9,000 prostates had been examined. Eighteen percent of the men who took finasteride were diagnosed with prostate cancer, while about 24 percent of men taking placebo developed the cancer.
“The prevention statistics are positive, but it’s important to remember that the benefit in terms of cancer reduction is still modest — it’s not a cure for prostate cancer — and the drug does have side effects, such as sexual dysfunction in a small percentage of men,” said study co-investigator Dr. Michael S. Cookson, associate professor of Urologic Surgery.
The study made a special cautionary note about the increased rate of higher grade tumors among the men on finasteride, and these tumors are associated with higher mortality rates.
“It has been known that men who have higher grade and more aggressive prostate cancers more frequently have a relatively low blood testosterone level,” Smith said. “Since finasteride decreases the level of male hormone within the cell, this may account for why more high-grade tumors were observed in the finasteride arm.
“Our treatments for prostate cancer continue to improve and methods such as robotic surgery to remove the prostate are decreasing side effects of treatments. However, further efforts at prevention are even more important and, fortunately, there are some other prevention strategies being tested,” he said.
The next large scale NIH-sponsored prevention study in prostate cancer is already underway at VUMC and continues to enroll volunteers. The Selenium and Vitamin E Cancer Prevention Trial, or SELECT, is a similar long-term cancer prevention trial. And, Cookson said, there are other potential cancer prevention drugs coming down the pike with different mechanisms of action and, possibly, fewer side effects. Some of these newer agents will also be used in future prevention trials.
For more information about participation in SELECT, call Vanderbilt’s Department of Urologic Surgery at 322-7300.