Supplementation with either selenium or vitamin E does not
appear to reduce the risk of prostate cancer or other cancers,
according to a study released on early December 9, 2008 Online in JAMA. This will be published on January 7, 2008, but has been released early due to the implications in public health.
Although deaths from prostate cancer in the United States has declined in recent years, this type of cancer is the second leading cause of cancer death in men, with 186,000 new cases and 29,000 deaths estimated for 2008. Consequently, the pursuit of effective chemoprevention methods has a high priority in research. Previously, it has been shown observationally that selenium and vitamin E have potential for prevention of prostate cancer, but observational studies are often affected by confounding influences.
To investigate the effects of selenium and vitamin E on cancer risk, Scott M. Lippman, M.D., of the University of Texas M. D. Anderson Cancer Center, Houston, and Eric A. Klein, M.D., of the Cleveland Clinic Lerner College of Medicine, Cleveland, and colleagues conducted a randomized controlled trial, called the Selenium and Vitamin E Cancer Prevention Trial (SELECT), in 35,533 men aged older than 50 years (for African-American men) or 55 years (for other men) in the U.S., Canada, and Puerto Rico. Each man began the study with no previous diagnosis and no signs of impending of prostate cancer. Each participant was randomized to one of four interventions: selenium (200 μg/day); vitamin E (400 IU/day), selenium and vitamin E simultaneously, or placebo.
Although follow-up was planned for seven to twelve years, after a median follow-up time of 5.46 years, the study was discontinued because the study's alternative hypothesis, that there is no benefit from either study agent, was convincingly demonstrated, and an independent data and safety monitoring committee concluded there was no possibility of a benefit for the duration of the planned study.
No statistically significant difference in prostate cancer diagnosis was found between the four groups, with each group having between four and five cases per 100 men. Some nonsignificant increased risks of prostate cancer (in the vitamin E only group) and type 2 diabetes mellitus (in the selenium only group) were seen.
The authors conclude that selenium and vitamin E supplementation have no role in the prophylaxis of prostate cancer. "In conclusion, SELECT has definitively demonstrated that selenium, vitamin E, or selenium + vitamin E (at the tested doses and formulations) did not prevent prostate cancer in the generally healthy, heterogeneous population of men in SELECT. These data underscore the prudence that is needed in considering recommendations to use agents for the prevention or control of disease in the absence of convincing clinical trial results. These findings also compel the medical research community to continue the search for new, effective agents for prostate cancer prevention," they write.
Effect of Selenium and Vitamin E on Risk of Prostate Cancer and Other Cancers: The Selenium and Vitamin E Cancer Prevention Trial (SELECT)
Scott M. Lippman, MD; Eric A. Klein, MD; Phyllis J. Goodman, MS; M. Scott Lucia, MD; Ian M. Thompson, MD; Leslie G. Ford, MD; Howard L. Parnes, MD; Lori M. Minasian, MD; J. Michael Gaziano, MD, MPH; Jo Ann Hartline, MPH; J. Kellogg Parsons, MD, MHS; James D. Bearden III, MD; E. David Crawford, MD; Gary E. Goodman, MD; Jaime Claudio, MD; Eric Winquist, MD, MSc; Elise D. Cook, MD; Daniel D. Karp, MD; Philip Walther, MD; Michael M. Lieber, MD; Alan R. Kristal, DrPH; Amy K. Darke, MS; Kathryn B. Arnold, MS; Patricia A. Ganz, MD; Regina M. Santella, PhD; Demetrius Albanes, MD; Philip R. Taylor, MD, ScD; Jeffrey L. Probstfield, MD; T. J. Jagpal, CCRP; John J. Crowley, PhD; Frank L. Meyskens Jr, MD; Laurence H. Baker, DO; Charles A. Coltman Jr, MD
Written by Anna Sophia McKenney