Vitamin E and the Risk of Prostate Cancer. Part 2
With considerable preclinical and epidemiological evidence that selenium and vitamin E may reduce prostate cancer risk, we conducted and reported the results of a prospective randomized trial examining the effect of these 2 agents for prostate cancer prevention. Coordinated by SWOG, a federally funded cancer research cooperative group, the Selenium and Vitamin E Cancer Prevention Trial (SELECT) began accrual on August 22, 2001, and randomized 35 533 men into 4 groups: selenium with matching placebo, vitamin E with matching placebo, both agents, or placebo.
Based on a preplanned interim analysis, the independent data and safety monitoring committee met on September 15, 2008, and recommended the early discontinuation of study supplements because of lack of efficacy for risk reduction and because futility analysis demonstrated no possibility of benefit to the planned degree with additional follow-up.6
As reported in the initial article,6 with a median follow-up of 5.5 years, the numbers of prostate cancers detected were 473 (hazard ratio [HR], 1.13; 99% CI, 0.95-1.35) for vitamin E; 432 (HR, 1.04; 99% CI, 0.87-1.24) for selenium; 437 (HR, 1.05; 99% CI, 0.88-1.25) for selenium plus vitamin E; and 416 (HR, 1.0) for placebo. Although these results were not statistically significant, the data and safety monitoring committee expressed concern about the increased risk of prostate cancer observed in the vitamin E plus placebo group, which approached statistical significance (P = .06) and a statistically nonsignificant increased risk of type 2 diabetes mellitus in the selenium plus placebo group (P = .16).
Since that time, participant follow-up has continued, allowing observation of additional events. On May 20, 2011, the data and safety monitoring committee reviewed trial data and recommended reporting the finding regarding increased risk of prostate cancer with vitamin E. This recommendation was based on final data collection from the study sites and coincided with the preplanned final analysis at 7 years after the last participant was randomized. Viagra professional Australia
Detailed descriptions of the rationale, design, conduct, and initial results of SELECT have been previously published. The study enrolled healthy men at average risk of prostate cancer based on a baseline prostate-specific antigen (PSA) of ≤4 ng/mL and normal digital rectal examination (DRE) commencing at age 50 years for black men or at age 55 years for all others. Men were randomized into 1 of 4 groups: selenium (200 μg/d from L-selenomethionine) with matching vitamin E placebo, vitamin E (400 IU/d of all rac -α-tocopherol acetate) with matching selenium placebo, both agents, or matching placebo.
Participants without prostate cancer were monitored every 6 months with an annual limited physical examination including blood pressure, weight, and smoking status; participants who developed prostate cancer during the study were monitored annually thereafter. Participants were recommended to undergo PSA and DRE testing and prostate biopsy based on the standard of care in their community and in accordance with the participant's preference. To facilitate adherence, a multivitamin containing no selenium or vitamin E was offered. All participants were required to provide written informed consent and the local institutional review board of each study site approved the study.