Daily supplements of selenium may not reduce the risk of lung cancer, say results from a major trial that adds more questions to the cancer-fighting ability of the mineral.
According to findings presented at the American Society of Clinical Oncology 2010 Annual Meeting, a daily supplement of 200 micrograms of selenium was just as ineffective as placebo for reducing the risk of lung cancer recurrence or second primary malignancy.
A benefit in a small number of lung cancer patients who never smoked was reported, but scientists led Daniel Karp, MD, from The University of Texas MD Anderson Cancer Center deemed this to not be statistically significant.
"Our results demonstrate that selenium is not an effective chemoprevention agent in an unselected group of lung cancer patients, and it's not something we can recommend to our patients to prevent a second cancer from developing or recurring," said Karp.
"These findings also remind us that never smokers may represent a unique disease and should be an area for special consideration for research focus.”
Karp and his co-workers recruited 1,522 people who were cancer-free at the time of enrollment but had previously undergone surgery to remove Stage I non-small cell lung cancer.
The study was stopped prematurely when an interim analysis revealed no general benefits, and a slightly higher progression-free survival in the placebo group compared with the selenium group. NutraIngredients has not seen the full data.
“Given our results and that of SELECT, physicians now can point to two large NCI-sponsored Phase III trials and tell patients that, at this time, the only definitive studies that have been conducted have been negative,” said Karp.
In January 2009 the Journal of the American Medical Association (JAMA, 2009, Vol 301, pp. 39-51) reported the results the high profile Selenium and Vitamin E Cancer Prevention Trial (SELECT) which found no differences between daily supplements of selenium, vitamin E, both, or placebo with regards the rosk of prostate cancer.
Commenting on the new findings, Andrew Shao, PhD., senior VP, Scientific & Regulatory Affairs, CRN told NutraIngredients-USA that the over-reliance on the results of the SELECT trial is short-sighted.
“[The researchers take] the results of SELECT at face value and fail to acknowledge important limitations of that study, including using a different form of selenium than that which had shown benefit in previous human trials, enrolling subjects with relatively high selenium status at baseline and the very few prostate cancer deaths that occurred in the trial - making it difficult to demonstrate a protective effect of the selenium intervention,” said Dr Shao.
"The present study was still a secondary prevention trial, enrolling patients who already had cancer, vs. a primary prevention trial like SELECT, in which the subjects were cancer-free at baseline. These are two different trials and the results cannot be lumped together as if they represent the same thing. I believe the selenium-cancer prevention relationship is complex and likely is highly dependent on baseline selenium status, which in this case we don't know, because we don't have the details on the study yet,” added Dr Shao.
Selenium and cancer
Selenium is a trace element that occurs naturally in the soil and is absorbed by plants and crops, from where it enters the human food chain - either directly or through consumption of meat and other products from grazing animals.
The mineral is included in between 50 and 100 different proteins in the body, with multifarious roles including building heart muscles and healthy sperm. However, cancer prevention remains one of the major benefits of selenium, and it is the only mineral that qualifies for a Food and Drug Administration (FDA)-approved qualified health claim for general cancer reduction incidence.
The claim reads: “Selenium may reduce the risk of certain cancers. Some scientific evidence suggests that consumption of selenium may reduce the risk of certain forms of cancer. However, FDA has determined that this evidence is limited and not conclusive.”
Last week, FDA was ordered to amend qualified selenium health claims by a Washington DC district court that found FDA’s addition of lengthy disclaimers to the claims to be in breach of Constitutional, First Amendment, free speech principles.
The court backed the plaintiffs –– in ordering the FDA to redraft disclaimers for selenium claims in relation to certain cancers and respiratory and digestive health benefits.
The decision was called a “momentous victory over FDA censorship”.by Virginia-based food attorney, Jonathan W Emord from the firm Emord and Associates, who acted as counsel to the plaintiffs: The Alliance for Natural Health USA, Durk Pearson and Sandy Shaw, and the Coalition Against FDA and FTC Censorship.
"The court held that FDA may not demand conclusive proof as a condition precedent for health claim allowance but must permit claims that accurately represent the state of credible scientific evidence linking nutrients to disease, so long as the inconclusiveness of the evidence is revealed to the public,” said Emord.