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Selenium and Vitamin E Cancer Prevention Trial

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The Selenium and Vitamin E Cancer Prevention Trial, or SELECT, was a clinical trial conducted with the goal of determining whether vitamin E and selenium supplements could prevent prostate cancer.[1] Enrollment for the trial began in 2001 and ended in 2004.[1] It cost approximately $114 million to conduct and was performed at over 400 different research centers.[2] It was primarily funded by the National Cancer Institute (NCI) and was carried out by SWOG.[1] It was stopped early because the supplements did not show any benefit in preventing prostate cancer. Subsequent research based on the trial has generally found that selenium and vitamin E do not prevent prostate cancer. Other research based on foods rich in selenium or Vitamin E, not supplements, suggests that there is limited evidence such foods may protect against some forms of cancer.[3]

Methodology

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The study followed over 35,000 men in the United States, Puerto Rico, and Canada, who were assigned randomly to receive either both a selenium and vitamin E supplement, selenium and placebo, vitamin E and placebo, or two placebos.[4] It was one of the largest cancer prevention trials ever conducted,[5] and was described by the NCI as "the largest-ever prostate cancer prevention study."[6] Selenium and Vitamin E were chosen because they are well known antioxidants and had other mechanisms by which they were thought to prevent cancer, and preclinical and smaller clinical studies had yielded very promising results.[6][7]

The study was originally planned to last for twelve years after enrollment began.[8] However, it was stopped early in 2008 because no protective effect of supplementation on prostate cancer risk was found, and because the results suggested that vitamin E might increase the risk.[1] About 17,000 participants from the original SELECT completed an additional four years of a Centralized Follow-Up from 2010 until May 31, 2014, when SELECT closed.[9] The follow-up involved sending questionnaires to participants annually, which they could also fill out online.[1]

Results

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Initial results were published in 2008 in JAMA.[10] The initial results found that the increase in risk associated with Vitamin E was "statistically nonsignificant",[10] which the researchers wanted to verify in a subsequent study.[11]

A subsequent 2010 study further described SELECT's results and found that neither selenium nor vitamin E, on their own or in combination, prevented prostate cancer.[12]

A 2011 study based on the trial found that the risk of prostate cancer was elevated by 17% in the group that took vitamin E supplements, which was statistically significant.[8][13]

A 2014 study based on SELECT data found that selenium supplementation increased the risk of high-grade prostate cancer in men who had a higher baseline selenium status.[14][15]

A 2014 Cochrane review found that SELECT raised concerns about a possible association between selenium supplements and an increase in risk of type 2 diabetes, alopecia and dermatitis. The review concluded that "no convincing evidence suggests that selenium supplements can prevent cancer in humans."[16]

References

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  1. ^ a b c d e Selenium and Vitamin E Cancer Prevention Trial Q&A
  2. ^ Simon, Harvey B. (17 September 2009). "Do Vitamins Prevent Prostate Cancer?". Chicago Tribune. Retrieved 17 November 2014.
  3. ^ World Cancer Research Fund, American Institute for Cancer Research (2007). "Food, Nutrition, Physical Activity, and the Prevention of Cancer: a Global Perspective" (PDF). Washington DC: AICR. Archived from the original (PDF) on 2013-03-10.
  4. ^ Neighmond, Patti (27 October 2008). "Study: Vitamin E Doesn't Prevent Prostate Cancer". NPR. Retrieved 17 November 2014.
  5. ^ Hatfield DL, Gladyshev VN (February 2009). "The Outcome of Selenium and Vitamin E Cancer Prevention Trial (SELECT) reveals the need for better understanding of selenium biology". Molecular Interventions. 9 (1): 18–21. doi:10.1124/mi.9.1.6. PMC 2718722. PMID 19299660.
  6. ^ a b Largest-Ever Prostate Cancer Prevention Trial Opens: 32,000 Men Sought to Test Vitamin E and Selenium
  7. ^ Klein EA, Thompson IM, Lippman SM, Goodman PJ, Albanes D, Taylor PR, Coltman C (2003). "SELECT: the selenium and vitamin E cancer prevention trial". Urologic Oncology. 21 (1): 59–65. doi:10.1016/S1078-1439(02)00301-0. PMID 12684129.
  8. ^ a b "Selenium, vitamin E supplements may up prostate cancer risk". UPI. 21 February 2014. Retrieved 17 November 2014.
  9. ^ SELECT Archived 2014-11-29 at the Wayback Machine
  10. ^ a b Lippman SM, Klein EA, Goodman PJ, Lucia MS, Thompson IM, Ford LG, et al. (January 2009). "Effect of selenium and vitamin E on risk of prostate cancer and other cancers: the Selenium and Vitamin E Cancer Prevention Trial (SELECT)". JAMA. 301 (1): 39–51. doi:10.1001/jama.2008.864. PMC 3682779. PMID 19066370.
  11. ^ Jaslow, Ryan (5 August 2013). "Too much vitamin E tied to prostate cancer risk". CBS News. Retrieved 17 November 2014.
  12. ^ Dunn BK, Richmond ES, Minasian LM, Ryan AM, Ford LG (2010). "A nutrient approach to prostate cancer prevention: The Selenium and Vitamin E Cancer Prevention Trial (SELECT)". Nutrition and Cancer. 62 (7): 896–918. doi:10.1080/01635581.2010.509833. PMID 20924966. S2CID 20297799.
  13. ^ Klein EA, Thompson IM, Tangen CM, Crowley JJ, Lucia MS, Goodman PJ, et al. (October 2011). "Vitamin E and the risk of prostate cancer: the Selenium and Vitamin E Cancer Prevention Trial (SELECT)". JAMA. 306 (14): 1549–56. doi:10.1001/jama.2011.1437. PMC 4169010. PMID 21990298.
  14. ^ Kristal AR, Darke AK, Morris JS, Tangen CM, Goodman PJ, Thompson IM, et al. (March 2014). "Baseline selenium status and effects of selenium and vitamin e supplementation on prostate cancer risk". Journal of the National Cancer Institute. 106 (3): djt456. doi:10.1093/jnci/djt456. PMC 3975165. PMID 24563519.
  15. ^ Press Association (21 February 2014). "Some vitamin supplements raise risk of cancer in men, research shows". The Guardian. Retrieved 17 November 2014.
  16. ^ Vinceti M, Filippini T, Del Giovane C, Dennert G, Zwahlen M, Brinkman M, et al. (January 2018). "Selenium for preventing cancer". The Cochrane Database of Systematic Reviews. 1 (2): CD005195. doi:10.1002/14651858.CD005195.pub4. PMC 6491296. PMID 29376219.
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