The other day in the doctors lounge a
colleague asked me if I had heard about a new study presented at AHA
showing a benefit of chelation therapy in diabetics. I'm not big on
sound bite medicine and often don't get around to reading, let alone
blogging about such things for a month or more. So I told him no I
hadn't, but it had better be an improvement over the recent TACT
study, which I thought was seriously flawed.
I found it Saturday over morning
coffee. And no, it was not an improvement over TACT. It was merely
a subgroup analysis of TACT itself. Most of you have heard the buzz
by now so I'll cut straight to the study, which was simultaneously
published in one of the Circulation journals. Here's the link.
From the paper:
Methods and Results—Patients received
40 infusions of EDTA chelation or placebo. A total of 633 (37%)
patients had diabetes mellitus (322 EDTA and 311 placebo). EDTA
reduced the primary end point (death, reinfarction, stroke, coronary
revascularization, or hospitalization for angina; 25% versus 38%;
hazard ratio, 0.59; 95% confidence interval [CI], 0.44–0.79; P less
than 0.001) for over 5 years. The result remained significant after
Bonferroni adjustment for multiple subgroups (99.4% CI, 0.39–0.88;
adjusted P=0.002). All-cause mortality was reduced by EDTA chelation
(10% versus 16%; hazard ratio, 0.57; 95% CI, 0.36–0.88; P=0.011),
as was the secondary end point (cardiovascular death, reinfarction,
or stroke; 11% versus 17%; hazard ratio, 0.60; 95% CI, 0.39–0.91;
P=0.017). However, after adjusting for multiple subgroups, those
results were no longer significant. The number needed to treat to
reduce 1 primary end point over 5 years was 6.5 (95% CI, 4.4–12.7).
There was no reduction in events in non–diabetes mellitus (n=1075;
P=0.877), resulting in a treatment by diabetes mellitus interaction
(P=0.004).
Conclusions—Post–myocardial
infarction patients with diabetes mellitus aged greater than or equal
to 50 demonstrated a marked reduction in cardiovascular events with
EDTA chelation. These findings support efforts to replicate these
findings and define the mechanisms of benefit. However, they do not
constitute sufficient evidence to indicate the routine use of
chelation therapy for all post–myocardial infarction patients with
diabetes mellitus.
The hype surrounding this paper will be
misleading. Before I get to that, some other links of interest. Here is a discussion piece from the Heart.org, now part of
Medscape Cardiology (free full text after registration). The piece
is less than appropriately critical of the study but does provide
some details for those without full text access to the original
paper. Also found at the Medscape site is this article by Dr.
John Mandrola (who blogs at Dr. John M). I think Dr. John is
way too kind to the study and his tone, as reflected in the title
Chelation Therapy: Promising for Diabetic Patients but Disruptive
to the Medical Establishment is
a little incendiary. From his introductory comments:
Based on this
analysis of TACT, only six patients with diabetes had to be treated
with chelation to prevent one adverse outcome. That's less than half
the NNT when statins are used in patients with diabetes and
established vascular disease—an uncontroversial indication.
Yet the medical
establishment is overcome with doubt.
What
does he mean by the medical establishment? If he means an organized
body of leaders in medicine who stand for good ethics and scientific
integrity, put me in that camp. That
medical establishment has good reason to be upset about TACT. But
perhaps Dr. John means something different. He says:
One of the doctors
whom I hold in highest regard sent this to me in relation to the
establishment:
The machine depends on people being
sick to function. If people take control of their own health, the
machine falls apart. And it is a billion-dollar business. Who
wouldn't aggressively denounce anything that threatens it?
The disruption
wrought by the new cholesterol guidelines pales in comparison to the
angst surrounding chelation therapy.
Dr.
John is talking around a very serious accusation: that professionals
in mainstream medicine don't want patients to get well and
stay well by taking charge of
their own health. It's a somewhat conspiratorial idea but popular
enough. The suggestion is that doctors in conventional medicine
don't want their patients to be empowered. Is that what he really
meant?
How
should we interpret the study? First the usual objections. Be
cautious about basing treatment recommendations on just one trial.
PROWESS
and many other studies taught us that lesson. (And keep in mind that
TACT is just one in the face of several prior studies all of which
were negative). Moreover we all know the hazards of subgroup
analysis.
But
more telling is a look at the peculiarities of TACT itself. With the
publication of the original study
in JAMA there was a companion editorial
by Dr. Steve Nissen that was appropriately critical. He said:
Execution
of a high-quality RCT requires skilled investigators and study
coordinators who understand these critical scientific principles. For
TACT, more than 60% of patients were randomized at enrolling centers
described as complementary and alternative medicine sites. Many of
these centers have websites that describe their services, which
include an array of unproven therapies ranging from stem cell therapy
to regrow breasts after mastectomy, high-dose intravenous vitamin C
to treat cancer, and use of cinnamon for treating diabetes to
treatment of influenza with antimicrobial essential oils or
homeopathic remedies (while warning patients not to undergo
immunization). Other sites offer chelation to treat or cure a variety
of conditions including autism in children. A common theme of these
centers is evident—they appear to attempt to appeal to vulnerable
patients who have challenging diseases by offering a variety of
unscientific and unproven therapies. Whether a high-quality RCT can
be performed at such sites is questionable.
For
an in depth look at what Nissen was referring to this article by Atwood and
colleagues is a must read. It reviews prior negative studies and
exposes what was really going on with TACT and, I believe, is
prerequisite to understanding the findings. It's compelling reading
and what you get from it is that TACT was badly (and in my reading of
the paper, hopelessly) flawed. That's why I ask in title of this
post how far the apple of the diabetes substudy can fall from the
tree of TACT.
What's
the take-home message? Here's Dr. John's:
It
would be a huge mistake to dismiss this science because chelation
does not conform to preconceived notions or because it is practiced
outside the mainstream of medicine. Let's not forget about the
patients with this terrible disease. It's not as if we have good
treatments for them.
The
authors have completely and thoroughly answered all questions posed
to them. The trial has been repeatedly inspected and vetted in two
prestigious peer-reviewed journals. Both the critics and TACT authors
agree that it is too early to recommend chelation therapy. But surely
the signal of benefit is strong enough to warrant confirmatory
trials. It is time to replicate these findings.
I
agree with him that this represents insufficient evidence to change
practice. I also agree we shouldn't dismiss something just because
it's outside mainstream. But the concerns about TACT are more basic.
They are about ethics and scientific standards. My take on the
study is not as optimistic as Dr. John's.
Not
only was TACT just one positive trial in the face of several negative
studies (a Bayesian analysis, I suspect,
would be unfavorable) but it was an anomaly. It's hard to read the
Atwood paper
and not come away thinking this trial was uniquely
flawed. Whether the findings of the TACT substudy even warrant
further research could be vigorously debated.