Selenium in Skin Cancer Patients
Selenium supplementation has been associated with cancer prevention benefits in animals, including antitumorigenic activity when given in supra-nutritional amounts. This trial represents the first double-blind, placebo-controlled cancer prevention trial to test whether selenium supplementation can reduce cancer risk in humans.
The study was performed in patients identified as having either a basal cell carcinoma (BCC) or squamous cell carcinoma (SCC) of the skin within the year prior to randomization. Selenium was supplied as 0.5 g high-selenium brewer’s yeast daily (= 200 mcg selenium) to 1312 persons, who were followed for a mean of 4.5 years. Primary end points were incidences of BCC and SCC. Secondary end points were all-cause mortality, total cancer mortality, total cancer incidence, and incidences of lung, prostate, and colorectal cancers.
BCC and SCC incidence were not influenced by selenium supplementation. On the other hand, selenium treatment was associated with a 0.83 RR all-cause mortality (not significant), a significant 0.5 RR total cancer mortality and 0.63 RR total cancer, and significant reduction in incidences of lung, colorectal, and prostate cancers.
The selenium dose employed was within normal U.S. dietary intake, although it was about twice the typical intake of the patients studied and 3-4 times the RDA. Corroborating the safe level of intake were an absence of dermatologic signs of selenosis and a plasma selenium below the EPA’s "no adverse effect" level. The beneficial results obtained in this study are insufficient to generate routine selenium supplementation but do provide substantial incentive for definitive studies to determine potential public health implications.
Clark L, et al. JAMA 1996;276: 1957-1963.
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