DECREASED INCIDENCE OF PROSTATE-CANCER WITH SELENIUM SUPPLEMENTATION - RESULTS OF A DOUBLE-BLIND CANCER PREVENTION TRIAL

Objective To test if supplemental dietary selenium is associated with changes in the incidence of prostate cancer. Patients and method A tot al of 974 men with a history of either a basal cell or squamous cell c arcinoma were randomized to either a daily supplement of 200 mu g of s elenium or a placebo. Patients were heated for a mean of 4.5 years and followed for a mean of 6.5 gears. Results Selenium treatment was asso ciated with a significant (63%) reduction in the secondary endpoint of prostate cancer incidence during 1983-93. There were 13 prostate canc er cases in the selenium-treated group and 35 cases in the placebo gro up (relative risk, RR=0.37, P=0.002). Restricting the analysis to the 843 patients with initially normal levels of prostate-specific antigen (less than or equal to 4 ng/mL), only four cases were diagnosed in th e selenium-treated group and 16 cases were diagnosed in the placebo gr oup after a 2 year treatment lag, (RR = 0.26 P = 0.009). There were si gnificant health benefits also for the other secondary endpoints of to tal cancer mortality, and the incidence of total, lung and colorectal cancer. There was no significant change in incidence for the primary e ndpoints of basal and squamous cell carcinoma of the skin. In light of these results, the 'blinded' phase of this trial was stopped early, C onclusions Although selenium shows no protective effects against the p rimary endpoint of squamous and basal cell carcinomas of the skin, the selenium-treated group had substantial reductions in the incidence of prostate cancer, and total cancer incidence and mortality that demand further evaluation in well-controlled prevention trials.