This article was first published in The Montreal Gazette.
Chelation therapy is the process of removing heavy metals from the body. It can be used to treat a child with lead poisoning or remove excess iron from the blood of someone with thalassemia. What it can’t do is treat heart disease, and the recent TACT2 trial should hopefully put the final nail in the coffin of this idea.
Chelation therapy involves the administration of medications that will bind to heavy metals like mercury, lead, arsenic or iron and allow them to be excreted by the body. It can be life saving in certain circumstances, like a child with acute lead poisoning and neurological symptoms. But chelation therapy is marketed far beyond its limited medical scope.
Some individuals promote chelation therapy to treat autism under the mistaken notion that mercury exposure causes autism. It doesn’t, but that hasn’t stopped many private clinics from administering this therapy to children. Chelation therapy can be dangerous: In 2005, the U.S. Centers for Disease Control and Prevention identified two cases of children dying during treatment, and the Food and Drug Administration has started to crack down on false claims that chelation can treat autism.
Its role in treating cardiovascular disease is equally tenuous. When pressed as to how it would work, proponents claim that chelation removes calcium from the bloodstream, which then prevents atherosclerosis and hardening of the arteries. But atherosclerosis is more complicated than too much calcium, and lowering calcium levels in the blood can be potentially dangerous and lead to fatal arrhythmias.
Despite the vague mechanism of action, chelation remained a popular service by alternative practitioners who would sell it as part of some general detox package.
Given the lack of benefit, a large randomized trial was commissioned to investigate the issue. The Trial to Assess Chelation Therapy (TACT), published 11 years ago, surprised many by claiming there was indeed a benefit for cardiovascular outcomes. But on closer inspection, there were some issues.
In an accompanying editorial published in JAMA, cardiologist Steven Nissen pointed out some of the problems at the time. TACT was primarily conducted not in a hospital or research setting, but in centres described as complementary and alternative medicine sites that already used chelation. Also, the chelation therapy involved not just the chelating agent disodium EDTA, but also high-dose vitamin C, magnesium, the anesthetic procaine and the blood thinner heparin.
There was a high dropout rate of 18 per cent in the study. While dropout and loss to followup does happen in clinical trials, it is rare to see it mostly in the placebo group, since it usually happens in those randomized to the treatment who experience side effects.
Finally, the researchers did many interim analyses of their study data. Ideally, you should wait until the end of a trial to analyze the data rather than “peeking” at the data halfway through. In practice, some interim analyses are necessary to ensure there is no safety signal or other issue with the study medication. But while one or two interim analyses would be normal, the TACT trial had 11, which is not in keeping with standard practice.
The journal editors had a number of concerns with the paper, but ultimately decided to publish it with all those caveats in place.
Despite all these concerns about the conduct of the study, the results of TACT were fairly modest, limited to a reduction in the need for future stents, and seemed to be most pronounced only in diabetics.
Hence, the TACT2 trial was launched to verify the results of TACT, and its results were recently published. There was no cardiovascular benefit to the 40 weekly intravenous infusions of disodium EDTA and the multivitamin cocktail that accompanied them.
Little more needs to be said on the subject of chelation therapy. It is unfortunate that it took more than a decade to refute the initial dubious results of TACT, but I suppose better late than never.
