No Benefit from Selenium and Vitamin E Supplements, Concludes Prostate Cancer Prevention Study

Selenium and vitamin E supplements, used together or separately, did not prevent prostate cancer, concluded a review of data from the Selenium and Vitamin E Cancer Prevention Trial (SELECT), funded by the National Cancer Institute (NCI; Rockville, MD).

In addition to this finding, data showed a small increase in the number of prostate cancer cases among the over 35,000 men age 50 and older in the trial taking only vitamin E and a small increase in the number of cases of adult onset diabetes in men taking only selenium. Neither of these findings proves an increased risk from the supplements, as findings are premature and could be coincidental, the study's authors concluded.

“(The study) was always designed (to) answer more than a single question about prostate cancer,” said Eric Klein, MD, study co-chair for SELECT. “As we continue to monitor the health of these 35,000 men, this information may help us understand why two nutrients that showed strong initial evidence to be able to prevent prostate cancer did not do so.”

Participants are receiving letters telling them to seize using the study’s supplements, and will continue to have their health monitored by study staff, SELECT said. Investigators intend to follow the participants for about three years to determine the long-term effects of having taken either a supplement or placebo.

SELECT was undertaken to validate a 1998 study of 29,133 male smokers in Finland who took vitamin E to prevent lung cancer. The study showed 32 percent fewer prostate cancers in men taking the supplement, and a 1996 study of 1,312 men and women with skin cancer who took selenium for prevention of the disease showed men who taking the supplement had 52 percent fewer prostate cancers than men who did not.

Men were recruited to participate in SELECT based on these findings. Participants were randomly assigned to take one of four sets of supplements or placebos, with more than 8,000 men in each group. One group took both selenium and vitamin E; one took selenium and a vitamin E placebo; one took vitamin E and a selenium placebo; and the final group received placebos of both supplements.

Prostate cancer is the most common type of cancer in men in the United States next to skin cancer. According to estimates, there will be approximately 186,320 new cases of prostate cancer and 28,660 deaths from this disease in the United States this year.