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SELENIUM SUPPLEMENTATION MAY REDUCE CANCER MORTALITY.

Some data suggest that selenium may have anti-tumor effects, possibly by protecting against oxidative damage. This multicenter, randomized, placebo-controlled trial tested the impact of oral supplementation of selenium in 1312 patients with a history of basal or squamous cell carcinoma of the skin.

The subjects were enrolled between 1983 and 1991, and treated for an average of 4.5 years with either 200 micrograms of selenium daily or placebo. At the end of the study (1993), 44 percent of subjects were still receiving treatment. There were no differences between groups in rates of basal or squamous cell skin cancer -- the primary end points. However, total cancer incidence was reduced by 37 percent in the selenium group; the selenium group had significantly lower rates of prostate cancer (relative risk, 0.37), colorectal cancers (RR, 0.42), and lung cancer (RR, 0.54). Multivariate analysis indicated a strong trend toward lower total mortality in the selenium group (RR, 0.79), largely due to a 50 percent reduction in total cancer mortality.

Comment: These intriguing results are compromised by the fact that total cancer incidence and mortality were not the primary end points of the study. An accompanying editorial concludes that it would be premature to market selenium for cancer prevention until this finding is confirmed in future randomized trials. If the effects of selenium are really as dramatic as this study suggests, it will not take long to confirm these results.

— TH Lee

Published in Journal Watch General Medicine January 14, 1997

Citation(s):

Clark LC et al. Effects of selenium supplementation for cancer prevention in patients with carcinoma of the skin: a randomized controlled trial. JAMA 1996 Dec 25 276 1957-1963.

• Medline abstract (Free)

Colditz GA. Selenium and cancer prevention: promising results indicate further trials required. JAMA 1996 Dec 25 276 1984-1985.

• Medline abstract (Free)