Positive Health Online

Abstract

CLARK and colleagues, Arizona Cancer Center, College of Medicine, University of Arizona, Tucson 85716 USA tested whether supplemental dietary selenium is associated with changed incidence of prostate cancer .

Background

Methodology

974 men with a history of either basal cell or squamous cell cancer were randomised to receive a daily supplement of 200 micrograms of selenium or a placebo. The men were treated for a mean of 4.5 years and followed for a mean of 6.5 years.

Results

Selenium treatment was associated with a significant (63%) reduction in the secondary endpoint of prostate cancer incidence during 1983-93. There were 13 prostate cancer cases in the selenium-treated compared with 35 in the placebo group (relative risk RR = 0.37). If the analysis is restricted to the 843 patients with initially normal levels of prostate-specific antigen (PSA), there were only 4 cases diagnosed in the selenium-treated group compared with 16 in the placebo group following a 2 year treatment lag (RR = 0.26). Other significant health benefits were observed also for the other secondary endpoints of total cancer mortality and incidence of total, lung and colorectal cancer. There were no significant changes in incidence for primary endpoints of basal and squamous cell skin cancer. In the light of these results, the "blinded" phase of this trial was stopped early.

Conclusion

Selenium treatment was associated with substantial reductions in the incidence of prostate cancer and total cancer incidence and mortality . Selenium did not show a protective effect against squamous and basal skin cancers.

References

Clark LC et al Decreased incidence of prostate cancer with selenium supplementation: results of a double-blind cancer prevention trial Br J Urol 81(5): 730-4 May 1998.