The Selenium and Vitamin E Cancer Prevention Trial (SELECT)
Principal Investigators (PIs):
- Catherine Tangen, Dr.P.H.
Fred Hutchinson Cancer Research Center
- Ian Thompson, M.D.
University of Texas Health Science Center, San Antonio
Funded Since: 2001
Funding Source: National Cancer Institute
Year(s) of Enrollment: 2001-2004
Study Website: http://www.swog.org/select
SELECT is a phase III randomized, placebo-controlled trial of selenium and/or vitamin E supplementation for prostate cancer prevention. The major eligibility requirements included age of ≥ 50 years for African American men and ≥ 55 years for all others, no prior prostate-cancer diagnosis, PSA ≤ 4 ng/mL, and a DRE not suspicious for cancer. Participants had semi-annual clinic visits. An extensive assessment of dietary supplement use was also collected at baseline and supplement use was updated annually. Annual prostate cancer screening with PSA and DRE was based on community screening standards. Prostate tissue samples were stored for future research. Adherence measures included pill counts and plasma levels of alpha- and gamma-tocopherol and plasma in a subset of 8% of subjects. Baseline plasma and toenails and white blood cells for DNA were collected on all subjects. In a nested case-cohort study, plasma and toenail selenium, plasma tocopherols, and extracted DNA have been obtained.
A total of 35,533 men (1800 previously on PCPT), were randomized from 427 sites in the U.S., Canada, and Puerto Rico achieving minority representation of 21% (15% African Americans). Study supplementation ended in 2008. During the course of the trial, four separately funded ancillary studies were activated. They included 1) the prevention of Alzheimer's disease (PREADVISE); 2) the adenomatous colorectal polyps (ACP) study; 3) the Eye Ancillary Study (SEE), which investigated the role of selenium and vitamin E on cataracts and age-related macular degeneration; and 4) the Respiratory Ancillary Study (RAS), which studies the effect of selenium and vitamin E on lung function decline.
Primary results were reported early (planned futility analysis) indicating neither vitamin E nor selenium supplements were associated with prevention of prostate cancer. An updated analysis in 2011 showed a statistically significant increased risk of prostate cancer in the vitamin E compared to placebo arms (hazard ratio 1.17, 99% confidence interval 1.00, 1.36). Follow-up continued for approximately half the participants after supplementation stopped; this included monitoring new prostate and other cancers. All subject follow-up will cease in the summer of 2014. However, there are plans for a National Death Index search to obtain cause of death information.