The initial results from the Nutritional Prevention of Cancer Trial reported in 1996 showed that selenium use did not influence the rate of nonmelanoma skin cancer in individuals who were at risk for this type of cancer. However, the new findings, which are based on three additional years of follow-up, suggest that use of the selenium, an antioxidant, may promote certain cancers.

These findings run counter to the results of animal studies that indicate a protective effect for selenium and other antioxidants (see Reuters Health story February 27, 1998).

The study, reported in the Journal of the National Cancer Institute, involved 1312 patients with a history of nonmelanoma skin cancer who were randomly assigned to receive daily supplementation with selenium 200 micrograms or placebo ("sugar pill").

In agreement with the initial results, selenium use was not associated with the risk of basal cell cancer, study author Dr. James R. Marshall, from the Roswell Park Cancer Institute in Buffalo, New York, and colleagues note.

However, use of the antioxidant seemed to raise the risk of squamous cell cancer, the researchers state. Selenium users were 25% more likely to develop this malignancy than nonusers.

These findings should be viewed along with the overall impact of selenium supplementation as a potential cancer-preventing agent, the authors note. Prostate cancer prevention trials that are now underway, including one testing selenium supplementation in men with precancerous cells in the prostate, "will help to clarify this overall impact," they add.

SOURCE: Journal of the National Cancer Institute, October 1, 2003.