'To Selenium, or not to Selenium' - that was Part of the 'Question'

A large trial like SELECT is the only way to determine for certain the real value of supplements

Arizona Cancer Center researchers now can answer one important question for millions of men in America who have been taking or thinking of taking the mineral Selenium and Vitamin E supplements to try to prevent prostate cancer.

As a result of the largest-ever trial on prostate cancer prevention, researchers have found that Selenium and Vitamin E do not aid in preventing prostate cancer. The Arizona Cancer Center was part of a network of research sites that collectively recruited men to take part in the SELECT (the Selenium and Vitamin E Cancer Prevention Trial) study sponsored by the National Cancer Institute.

Millions of Americans use dietary supplements, vitamins and minerals to try to protect their health and prevent disease without concrete scientific evidence of the benefits or dangers of doing so.

“A large trial like SELECT is the only way to determine for certain the real value of supplements,” said Fredrick Ahmann, MD, professor of medicine and director of the Hematology/Oncology Fellowship Program at the Arizona Cancer Center. “Using science to study and determine whether there is value to taking a specific substance for health or disease prevention is vital, telling us what is helpful, what is harmful and what is not useful to take.”

The genesis for SELECT was based in previous research studies of Selenium and Vitamin E for other cancers. These studies suggested that the nutrients might reduce the risk of developing prostate cancer. Healthy men 55 or older (50 or older for African Americans) were recruited to participate in a 15-year study to see whether Selenium and Vitamin E would protect against prostate cancer, the leading cause of cancer death in men after skin cancer. Some 35,000 men were enrolled nationally; in Tucson, about 240 men were enrolled at the Arizona Cancer Center and 70 at the Southern Arizona VA Health Care System.

During a clinical trial, an independent Data and Safety Monitoring Committee “un-blinds” the study yearly to do a statistical evaluation, and five years into this study its analysis determined there is no evidence to justify having men continue to take the supplements.

SELECT is continuing to evaluate the effects of the supplements, but participants no longer are taking study supplements. The independent Data and Safety Monitoring Committee for the trial found that Selenium and Vitamin E taken alone or together for an average of five years did not prevent prostate cancer. SELECT participants are being informed about the initial findings and told to stop taking their study supplements. Men in the study will continue to have their health monitored by study staff, continue to respond to the study questionnaires and will provide a blood sample at their five-year anniversary of joining the trial (if they have not already done so). The information from the questionnaires and the blood samples will allow a complete analysis of the study, including important molecular-level research on the role of antioxidants in cancer prevention and the natural history of prostate cancer, other cancers and diseases of male aging.

The SELECT data showed two concerning, but not statistically significant, trends: there were slightly more cases of prostate cancer in men taking only Vitamin E and slightly more cases of diabetes in men taking only Selenium. Neither of these findings proves an increased risk from the supplements and may be due to chance.
The Arizona Cancer Center is the state’s premier National Cancer Institute-designated comprehensive cancer center. With primary locations at The University of Arizona in Tucson and in Scottsdale, the Center has more than a dozen research and education offices throughout the state and 300 physician and scientist members working to prevent and cure cancer. For more information, please go to www.azcc.arizona.edu.