Two dietary supplements, selenium and vitamin E, will be tested
The University of Maryland Greenebaum Cancer Center in Baltimore is one of more than 400 sites in the U.S., Puerto Rico and Canada evaluating whether two powerful antioxidants -- selenium and vitamin E -- might prove effective at preventing prostate cancer.
"This is the largest prostate cancer prevention study ever conducted," says Nancy Dawson, M.D., a prostate cancer specialist who heads the division of Genitourinary Oncology at the University of Maryland Greenebaum Cancer Center and is a professor of medicine at the University of Maryland School of Medicine. "If the intake of two nutritional supplements can help prevent or delay this deadly disease, many more men can take a proactive approach to preventing prostate cancer, which currently affects one out of every six men. It is the most common cancer among men and is the second-leading cause of cancer death."
The Selenium and Vitamin E Cancer Prevention Trial, known as SELECT, is sponsored by the National Cancer Institute and the Southwest Oncology Group. Based on preliminary study results looking at their preventive effects on other cancers, both selenium and vitamin E were found to cut prostate cancer risk by 30 to 60 percent.
In 1996, the Journal of the American Medical Association reported impressive results from a study of selenium and its potential at preventing skin cancer. Although selenium did not reduce the incidence of basal cell carcinoma or squamous cell carcinoma of the skin, the participants in the selenium group had 63 percent fewer cases of prostate cancer than the non-selenium group. There were also 58 percent fewer cases of colorectal cancer and 46 percent fewer cases of lung cancers compared to the placebo group.
"The purpose of the SELECT trial is to study the effects, both good and bad, of selenium and vitamin E on prostate cancer prevention. Though other scientific studies have noted a beneficial effect from both dietary supplements, there has not been a single, large-scale study devoted to studying the effects of either with regard to prostate cancer," says Dr. Dawson. "This trial represents that first effort." More than 32,000 participants in the SELECT study will be randomly assigned to one, both or neither of the nutritional supplements. Two hundred micrograms of selenium and 400 International Units of vitamin E per day will be used. Previous studies have shown these amounts to be safe.
This is a 12-year, double-blind study in which neither participants nor researchers know whether the capsules, all provided free of charge, are vitamins or placebos. Participants are asked not to take multi-vitamins that include selenium or vitamin E. Instead they and their significant others will be provided with specially-made multi-vitamins without those supplements. Participants also will need to visit the study site every six months and will be contacted twice by phone during the first year to monitor progress and answer questions. Participants annually may also have a limited medical exam, a digital rectal examination and a blood test for prostate specific antigen (PSA).
"By age 50, one-third of all American men have microscopic signs of the disease and by age 75, up to 75 percent of men have cancerous changes in their prostate," adds Dr. Dawson. "This year alone, nearly 180,000 American men will learn they have prostate cancer and 37,000 will die of this disease." The risk of prostate cancer also increases with age and is highest among African- American men, who also are affected at younger ages. African-American men age 50 years and older are eligible to participate in the SELECT trial and men of other ethnic groups aged 55 and older are eligible. Individuals previously diagnosed with prostate cancer are ineligible. Participants also must have a total PSA less than 4ng/ml and may not have had any other cancer malignancy within the last five years other than basal or squamous cell carcinoma.
"The medical community is becoming increasingly aware of the vital role that selenium, in particular, may have not only in preventing cancer, but other diseases such as heart disease, arthritis and hypothyroidism," says Dr. Dawson. "Exactly why selenium is showing such impressive results remains to be discovered."
Consumers should note that both selenium and vitamin E may be harmful in high doses. Side effects of selenium overuse may include hair loss, nail sloughing, mild nausea, bad breath, coughing, bronchitis, dizziness, weakness, skin redness or rash, irritability and tiredness. Male smokers with uncontrolled hypertension may be at greater risk of stroke when taking vitamin E.
"Our bodies need both selenium and vitamin E," says Dr. Dawson. "Selenium is a trace mineral typically found in soil. We get selenium in our water and food, especially in seafood, meats and Brazil nuts. We get vitamin E in a wide range of foods, especially vegetables, vegetable oils, nuts and egg yolks. Both are anti-oxidants believed to help control the cell damage that can lead to cancer."
Persons interested in this clinical trial may call 1-800-492-5538 for more information or visit http://data.umms.org/scripts/trials/index.cfm.