The Nutritional Prevention of
Cancer Trial was a double-blind, randomized, placebo-controlled clinical trial designed to test whether
selenium as selenized yeast (200 microg daily) could prevent nonmelanoma
skin cancer among 1312 patients from the Eastern United States who had previously had this disease. Results from September 15, 1983, through December 31, 1993, showed no association between treatment and the incidence of basal and
squamous cell carcinomas of the skin. This report summarizes the entire blinded treatment period, which ended on January 31, 1996. The association between treatment and time to first nonmelanoma
skin cancer diagnosis and between treatment and time to multiple skin
tumors overall and within subgroups, defined by baseline characteristics, was evaluated. Although results through the entire blinded period continued to show that
selenium supplementation was not statistically significantly associated with the risk of
basal cell carcinoma (hazard ratio [HR] = 1.09, 95% confidence interval [CI] = 0.94 to 1.26),
selenium supplementation was associated with statistically significantly elevated risk of
squamous cell carcinoma (HR = 1.25, 95% CI = 1.03 to 1.51) and of total nonmelanoma
skin cancer (HR = 1.17, 95% CI = 1.02 to 1.34). Results from the Nutritional Prevention of
Cancer Trial conducted among individuals at high risk of nonmelanoma
skin cancer continue to demonstrate that
selenium supplementation is ineffective at preventing
basal cell carcinoma and that it increases the risk of
squamous cell carcinoma and total nonmelanoma
skin cancer.