Selenium and vitamin E for prostate cancer: post-SELECT (Selenium and Vitamin E Cancer Prevention Trial) status.

Various formulations of selenium and vitamin E, both essential human dietary components, have been shown to possess a therapeutic and preventive effect against prostate cancer. Fortuitous results of clinical trials also implied a risk-reduction effect of selenium and vitamin E supplements. The Selenium and Vitamin E Cancer Prevention Trial (SELECT), using oral selenium and vitamin E supplementation in disease-free volunteers, was designed to test a prostate cancer chemoprevention hypothesis. SELECT was terminated early because of both safety concerns and negative data for the formulations and doses given. Here, we review and discuss the studies done before and since the inception of SELECT, as well as the parameters of the trial itself. We believe that there is a lack of appropriate in vivo preclinical studies on selenium and vitamin E despite many promising in vitro studies on these agents. It seems that the most effective doses and formulations of these agents for prostate cancer chemoprevention have yet to be tested. Also, improved understanding of selenium and vitamin E biology may facilitate the discovery of these doses and formulations.