The recent report of the diabetes portion of a big clinical study called TACT (Trial to Assess Chelation Therapy) seems to indicate that a well-criticized snake-oil therapy, “chelation therapy,” might be worth using in people with diabetes who have had a prior myocardial infarction.
“Chelation therapy” has been used (or better phrased, abused) by charlatans for years. Fringe practitioners have used a prescription medication, EDTA, which is FDA-approved for use in treatment of poisoning with what are called "heavy metals:" lead, cadmium, and mercury. These practioners claim that EDTA, combined with vitamins and minerals, can treat arteriosclerosis (hardening of the arteries). Further discussion of this use/abuse may be found on-line at the University of Maryland Medical Center, in an article titled Ethylenediaminetetraacetic acid and at Quackwatch, Chelation Therapy: Unproven Claims and Unsound Theories.
I must admit that I have been extremely biased against EDTA chelation therapy in general when used for anything except heavy metal poisoning. Tantalizingly, the recent TACT study doesn’t quite answer the question: does EDTA chelation therapy really work for PWD?
The parent study, Effect of Disodium EDTA Chelation Regimen on Cardiovascular Events in Patients With Previous Myocardial Infarction, was published in March 2013 in the Journal of the American Medical Association. The study measured five endpoints (death, myocardial infarction, stroke, coronary revascularization, and hospitalization for angina). The authors reported that, when the endpoints were combined, the patients who received chelation did slightly better overall than those who received a placebo. However, none of the endpoints when measured alone reached statistical significance, and there was also a high dropout rate: only 65% of patients completed all of the planned infusions and 30% dropped out. The authors concluded that “These results provide evidence to guide further research but are not sufficient to support the routine use of chelation therapy for treatment of patients who have had an MI.”
In an accompanying editorial, a well-known cardiologist, Dr. Steven Nissen, severely criticized the study, concluding that “Given the numerous concerns with this expensive, federally funded clinical trial, including missing data, potential investigator or patient unmasking, use of subjective end points, and intentional unblinding of the sponsor, the results cannot be accepted as reliable and do not demonstrate a benefit of chelation therapy.”
But his criticism of the main study didn’t stop the authors from looking at the data they had on PWD who had been in the study, and publishing the substudy findings, The Effect of an EDTA-based Chelation Regimen on Patients With Diabetes Mellitus and Prior Myocardial Infarction in the Trial to Assess Chelation Therapy (TACT) .
As an aside: as is usual when non-diabetes researchers look at diabetes, there was no effort made to stratify the PWD into excellent vs. lousy control (there’s no mention of A1C levels anywhere in the publication!), and hence no way to tell if the results that were observed were related to hyperglycemia or to any other possibilities.
In the TACT study, 633 patients had diabetes mellitus (322 were treated with EDTA and 311 with placebo). The researchers found that the EDTA-treated group had less of the endpoints of death, repeat myocardial infarction, stroke, coronary revascularization, or hospitalization for angina: 25% versus 38%. However, after doing the necessary adjustments for multiple subgroups, the results were no longer statistically significant. The authors none-the-less concluded that “Post–myocardial infarction patients with diabetes mellitus aged ≥50 demonstrated a marked reduction in cardiovascular events with EDTA chelation.”
The NIH has put out a press release about these diabetes findings, Chelation therapy reduces cardiovascular events for older patients with diabetes. The press release points out that TACT was not designed to discover how or why chelation might benefit patients with diabetes, and concludes “Additional studies are needed before we can determine the potential place of EDTA chelation therapy, if any, in the treatment of patients with coronary artery disease and diabetes.”
This whole idea of using EDTA in diabetes must be viewed as highly experimental. Therefore, I do have one bit of advice for PWD who hear about this study, and want to try EDTA: don’t... unless you sign up to become part of a subsequent study (“TACT-TWO”?) that would focus on diabetes, stratify patients by A1C, and which would someday see if the reported outcomes can be reproduced.