The US federal government is ending a prostate cancer study that involved 35,000 men because the treatment supplements of vitamin E and selenium are ineffective and there's a hint of risk.
Prostate cancer is the ninth most common cancer worldwide, but is the number one non-skin cancer among American men. It seems that this type of cancer affected 18 percent of US men and led to death of 3 percent in 2005 only. According to the estimates of the American Cancer Society, about 186,000 men will be diagnosed with prostate cancer by the end of this year. Almost 28,000 men loose the battle with the disease each year. Over 90 percent of prostate cancers are spotted when it is still confined to the prostate, a gland in the male reproductive system, or has extended to close parts of the body within the pelvis.
Previous studies suggested that higher doses of antioxidants like Vitamin E and selenium, both of which exist in relatively small amounts in food, might help prevent prostate cancer.The SELECT study:
The $119 million study - called the Selenium and Vitamin E Cancer Prevention Trial, or SELECT - of more than 35,000 men in their 50s and older began back in 2001 and was scheduled to run until 2012. During the trials conducted at over 400 sites in the United States, Canada and Puerto Rico, doctors gave combinations of Vitamin E, the mineral selenium, and a placebo.
An independent review of the study data shows that selenium and vitamin E supplements failed to prevent prostate cancer, according to the National Cancer Institute.
“Taking selenium or Vitamin E at the doses that we used in the SELECT trial for an average of five years did not prevent prostate cancer,” CBS News quoted Dr. Eric Klein, one of the researchers, as saying.
The National Cancer Institute also said there were slight increases in cancer cases among the group of men who took only vitamin E, and slightly more selenium-only users were getting diabetes. Klein said neither was statistically significant. "My guess is that these findings are due to chance," he said.
The NCI announced Monday that over the next few days participants in the study will begin receiving letters explaining the review and telling them to stop taking the supplements.
Klein said participants will continue to have their health monitored over the next two to three years. He said he does not foresee any serious problems.
Participants did not know which nutrients they were assigned to take, or if they were in a placebo group. If they ask now, doctors will tell them. But researchers say the study's results will be more accurate if most of the men wait to find that out until the followup health tracking is complete.Related studies
Scott M. Lippman, Eric A. Klein, Phyllis J. Goodman, M. Scott Lucia, Ian M.
Thompson, Leslie G. Ford, Howard L. Parnes, Lori M. Minasian, et al. , Effect of Selenium and Vitamin E on Risk of Prostate Cancer and Other Cancers
, J. Am. Med. Assoc., 301/1 (2009). doi: 10.1001/jama.2008.864
Eric A. Klein, Ian M. Thompson, Update on chemoprevention of prostate cancer
, Curr. Opin. Urology, 14/3 (2004) 143-149. DOI: 10.1097/01.mou.0000126550.26304.67
D.W. Nyman, M.S. Stratton, M.J. Kopplin, B.L. Dlakin, R.B. Nagle, A.J. Gandolfi, Selenium and selenomethionine levels in prostate cancer patients
, Cancer Detect. Prevent., 28 (2004) 8-16. doi: 10.1016/j.cdp.2003.11.002
Emmanuelle Meuillet, Suzanne Stratton, Durga Prasad Cherukuri, Anne-Christine Goulet, Jacob Kagey, Bruce Porterfield, Mark A. Nelson, Chemoprevention of prostate cancer with selenium: An update on current clinical trials and preclinical findings
, J. Cell. Biochem., 91/3 (2003) 443-458. DOI: 10.1002/jcb.10728
A.M.Y. Nomura, J. Lee, G.N. Stemmermann, G.F. Combs Jr., Serum Selenium and Subsequent Risk of Prostate Cancer, Cancer Epidemiol. Biomarkers Prev., 9/9 (2000) 883-887. available from: http://cebp.aacrjournals.org/cgi/content/full/9/9/883
L.C. Clark, B. Dalkin, A. Krongrad, G.F. Combs, B.W. Turnball, E.H. Slate, R. Witherington, J.H. Herlong, E. Janosko, D. Carpenter, C. Borosso, Decreased incidence of prostate cancer with selenium supplementation: results of a double-blind cancer prevention trial
, Br. J. Urol. , 81 (1998) 730-734. doi: 10.1046/j.1464-410x.1998.00630.x Related EVISA Resources EVISA Link Database: Selenium in human health EVISA Link Database: Selenium and Vitamin E Cancer Prevention Trial EVISA Link Database: Selenium and its relationship to cancer Related News EVISA News, March 16, 2008: New selenium-containing proteins identified in selenium-rich yeast EVISA News, April 9, 2007: Trimethylselenonium is not the major metabolite for human cancer patients excreting high doses of selenium EVISA News, October 6, 2005: Selenomethionine shows promising results as a protective agent against Esophageal Cancer EVISA News, August 2, 2005: New CRM for Selenomethionine in yeast developed by NRC Canada is now on the market
last time modified: December 11, 2008