SAN ANTONIO (Dec. 8, 2008) — A national study that involved The University of Texas Health Science Center at San Antonio and area men concluded that two health supplements do not prevent prostate cancer, despite promising results in two previous studies.
“If you’re taking vitamin E or selenium to prevent prostate cancer, you could better spend your money elsewhere, such as on a gym membership or a new pair of running shoes,” remarks one of the study’s authors, Ian M. Thompson, Jr., M.D., professor and chairman of urology. He directs the genitourinary clinic at the Cancer Therapy & Research Center (CTRC) at the UT Health Science Center.
The research will appear in the Dec. 9 issue of the Journal of the American Medical Association. Until this study, vitamin E and selenium represented the best hope for prostate cancer prevention, apart from prescribed medication, Dr. Thompson says. He estimates that half of healthy men over 50 are taking either of these supplements or both to prevent prostate cancer.
The Selenium and Vitamin E Cancer Prevention Trial, known as SELECT, enrolled more than 35,000 relatively healthy men in the U.S., Canada and Puerto Rico. In San Antonio, men were seen at the UT Health Science Center and Wilford Hall Medical Center. They were randomly selected to receive one of four options: 1) selenium, 2) vitamin E, 3) both supplements, or 4) a placebo. Neither the patients nor their physicians knew which option they received.
Leaders of the study, administered by the Southwest Oncology Group in San Antonio and Ann Arbor, Mich., told research sites to stop giving participants the supplements October 23 in year seven of the 12-year trial at the recommendation of an oversight committee. The evidence “convincingly demonstrated no benefit from either study agent,” according to the article.
Why were selenium and vitamin E ineffective in SELECT? The authors cite a few possibilities. One is that SELECT was specifically designed to test the effectiveness of the two supplements, while previous studies were not; in those other smaller studies, the cancer prevention effect may have been merely due to chance. There also were differences between SELECT and previous trials in formulations, dosages and patient characteristics.
“If healthy men want to invest in prevention, they should ask their physicians about the drug finasteride,” Dr. Thompson says. “If men at risk for prostate cancer took finasteride, 50,000 men destined to be diagnosed in 2009 would not get this cancer.”
Prostate cancer is diagnosed in 200,000 U.S. men each year. Finasteride was found to reduce a man’s risk of prostate cancer by 25 percent in a large study, the National Cancer Institute’s Prostate Cancer Prevention Trial coordinated by Dr. Thompson. He says the drug, available as a generic, has several benefits. It shrinks the size of a man’s prostate gland, reduces the risk of needing prostate surgery and improves urination, among others. On the downside, it reduces the volume of ejaculate, carries a 1 percent to 2 percent risk of breast tenderness, requires a prescription and costs $30-$40 a month.
Finasteride is the only preventive agent on the U.S. market that has been proven to prevent prostate cancer, Dr. Thompson says. Another drug, dutasteride (Avodart), used to treat prostate enlargement, is being tested.
Dr. Thompson occupies the Henry B. and Edna Smith Dielmann Memorial Chair in Urologic Science at the UT Health Science Center and the Glenda and Gary Woods Distinguished Chair in Genitourinary Oncology at the CTRC.
Note to media: Dr. Thompson will be available for interviews Monday, Dec. 8. Please call Karen Stamm to schedule.
The Cancer Therapy & Research Center (CTRC) at The University of Texas Health Science Center at San Antonio is one of the nation’s leading academic research and treatment centers, serving more than 4.4 million people in the high-growth corridor of Central and South Texas including Austin, San Antonio, Laredo and the Rio Grande Valley. CTRC is one of a few elite cancer centers in the country to be named a National Cancer Institute (NCI)-Designated Cancer Center, and is one of only three in Texas. CTRC handles more than 120,000 patient visits each year and is a world leader in developing new drugs to treat cancer. The CTRC Institute for Drug Development (IDD) is internationally recognized for conducting the largest oncology Phase I clinical drug studies program in the world. IDD has participated in the clinical and/or preclinical development of many of the cancer drugs approved by the U.S. Food & Drug Administration. For more information, visit www.ctrc.uthscsa.edu.