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Carotid endarterectomy evaluation Goals common to all neurologists.

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EDITORIAL
Carotid Endarterectomy Evaluation: Goals
Common to All Neurologists
The North American Symptomatic Carotid Endarterectomy Trial (NASCET) was only 3 years into its proposed 5-year program when an abrupt and unexpected
halt was announced to the randomization of patients
with very severe stenosis. It was disclosed from the
platform of the Annual Stroke Meeting of the American Heart Association that 17 strokes would be prevented in 2 years for every 100 similar patients with
very severe symptomatic stenosis who were treated by
this procedure by surgeons of a capability equal to
those involved in NASCET El].
In theory, this early cessation of part of a trial evaluating a surgical intervention or, for that matter, of a
drug evaluation, could have occurred for any one of
three reasons. First, the treatment might have had a
benefit that was actually more impressive from previous studies than was teing acknowledged by those who
proposed the need for the trial. This was scarcely the
case with NASCET. One million of these procedures
had been performed already and still there was a lack of
widespread agreement about its appropriate indications
[2]. Second, the speed of recruitment of the required
number of patients might have exceeded all predictions. This was far from the truth. At the beginning of
the trial, we calculated that we would recruit 3,000
patients by the end of the second year. Instead of
achieving this optimistic estimate, we had recruited
1,367 patients, of whom 659 had severe stenosis and
708 had moderate stenosis. Less than one-half of our
2-year target number was reached by the end of 3
years.
The third possibility: The process under study was
more malignant than was anticipated by the information that led to the preliminary sample-size calculations. Clearly, this was the main factor that triggered
the whistle-blowing on the portion of NASCET dealing with the patients with very severe stenosis. The
available but scanty literature on the subject led us to
assume that the annual stroke and death rate was between 6 % and 7% for patients with these severe and
symptomatic lesions. We set out believing that we
needed to obtain 1,300 of such “severe” patients.
When the confidential analyses invoked our Stopping
Rules for the 659 patients, the stroke and death rate
at 2 years was 32.396. The only hard data on this precise group of patients emerged from this study and the
parallel European Carotid Surgery Trial (ECST) E37. In
the NASCET patients, this symptomatic lesion proved
to be fourfold as serious from the prognostic viewpoint
as previously believed. The existing and meager evidence had been grossly misleading.
Patients with symptoms due to moderate stenosis
(30-69%) with and without ulceration remain in a
therapeutic wilderness with no clear signposts directing
us to the choice of a medical route alone or to medical
therapy in combination with endarterectomy. At the
lower end of severity of stenosis, the European trial
has provided evidence that patients with <30% stenosis were not helped with surgery over a follow-up period averaging 6 years. At the other end of the scale,
the NASCET data indicated a declining benefit as the
degree of stenosis fell from the tenth to the eighth
decile. The difference between medical and surgical
benefit for survival free of ipsilateral stroke at 2 years
was 27% at 29096, but was down to 12% when the
stenosis was between 7096 and 79%. A profile of recognized vascular and specific carotid risk variables had
an impact on the relative benefit in the severe group,
but despite this, surgery emerged as the best treatment
in all groups studied. A combination of risk profile and
degree of stenosis likely will determine who would
and should not be submitted to carotid surgery for
symptoms associated with stenosis between 30% and
69%.
NASCET needs the help of all North American
readers of this journal to complete this evaluation of
carotid endarterectomy in a timely fashion. The ExtracranidIntracrania1 Bypass Study and now the first
phases of NASCET and of the European trial have
established the feasibility of drawing credible and definitive conclusions from multicenter randomized trials
comparing medical treatment alone with medical treatment plus surgery [4]. Participating surgeons have
been prepared to submit their work to the critical scrutiny of their medical colleagues; surgeons and neurologists have been willing to collaborate more closely than
has sometimes been their pattern of practice; both have
been willing to adhere to the demands of modern trial
methodology and biostatistics. Many additional practicing neurologists outside and within the major academic
institutions and their patients must be persuaded to
become more frequently involved to ensure that NASCET is successfully concluded in a reasonable period
of time. New centers are not needed, but more patients are.
Cardiologists and cardiology departments have given
a clarion-clear signal of their willingness to give vigorous support to trials related to myocardial ischemia,
832 Copyright 0 1992 by the American Neurological Association
A total of 45,856 patients were entered by practicing
cardiologists into the Third International Study of Infarct Survival (ISIS-3) between September 1989 and
January 1991: a mere 19 months. By March 1992, the
results of ISIS-3 were published {5]. Even allowing for
a 10-fold increase in the number of centers involved
and the fact that myocardial infarction is considerably
more common than symptomatic carotid stenosis, this
feat of the ISIS-3 investigators stands as a challenge to
all physicians who would exchange persisting ignorance
for reasonable certainty. When the first 5 years of the
NASCET grant expires in August 1992, 1,100 patients
with moderate stenosis as well as the previous 659
patients with severe disease will have been randomized
from 80 centers. The study will complete its enrollment in March 1996. At least 1 year and, just possibly,
2 years could be taken from this if every academic
department of neurology and many neurologists in
community hospitals across North America were to
assume an aggressive interest in driving this inquiry to
an earlier conclusion. The restraints of practice plans
and practice patterns create difficulties, but they are
not insurmountable. A mere handful of patients per
year from each academic neurology department and
from every busy practicing neurologist is all that is required. There are enough centers participating to make
travel to them a simple matter for the patients. Nobody
will gain more from the definitive answer to this burning issue than will these patients and all those like them
in the future.
The profession, the patients, and the investigators
of NASCET will be indebted to all academics and all
neurological practitioners who use the following telephone number, which will make it simple to identify
their nearest collaborating institution: 1-800-565-6331.
Our European counterparts can contact ECST by
calling 031-343-6639 in Edinburgh.
H . J . M. Barnett, M D
Robarts Research Institute
P. 0. Box 5015, 100 Pertb Drive
London, Ontario, Canaak
References
1. NASCET Collaborators. Beneficial effect of carotid endarterectomy in symptomatic patients with high-grade carotid stenosis. N
Engl J Med 1991;325:445-453
2. Winslow CM, Solomon DH, Chassin MR, et al. The appropriateness of carotid endarterectomy. N Engl J Med 1988;318:
721-727
3. European Carotid Surgery Trialists’ Collaborative Group. MRC
European Surgery Trial: interim results for symptomatic patients
with severe (70-99%) or with mild (0-29%) carotid stenosis.
Lancet 1991;337: 1235 - 1243
4. The ECAC Bypass Study Group. Failure of extracranialintracranial arterial bypass to reduce the risk of ischemic stroke.
Results of an international randomized trial. N Engl J Med
1985;313:1191- 1200
5. ISIS-3. A randomised comparison of streptokinase vs tissue plasminogen activator vs anistreplase and of aspirin plus heparin vs
aspirin alone among 41,299 cases of suspected acute myocardial
infarction (Third International Srudy of Infarct Survival Collaborative Group). Lancet 1992;339:753-770
Editorial: Barnett: Carotid Endarterectomy Evaluation 833
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