Conflicting Results of Carotid-Stent Trials Frustrate Practical Application

Stenting of the carotid artery is a less invasive and potentially safer alternative to traditional endarterectomy (CEA) for the treatment of stenotic plaque. However, the relative efficacy of carotid stenting to prevent stroke has been unclear—a fact that has informed limited Medicare coverage for the procedure in the United States. Unfortunately the efficacy of carotid stenting remains unsettled after the recent release of conflicting results from 2 large, non-blinded studies.

Thursday the Lancet and Lancet Neurology published data from the International Carotid Stenting Study (ICSS), which showed a significantly higher incidence of ischemic stroke and related events after stenting. But results from the Carotid Revascularization Endarterectomy Versus Stenting Trial (CREST), which were presented Friday at the International Stroke Conference, revealed comparable rates of stroke, MI, or death with the 2 procedures.

Salient differences between the 2 studies, which include different patient populations and primary endpoints, are tabulated here. The main difficulty when attempting to conclude anything practical from the studies' results is that there are no easy apples-to-apples comparisons.

* For interim safety analysis. The primary outcome of the ICSS is fatal or disabling stroke at 3 years; results are expected in 2012.
** Statistically significant, stenting vs CEA.

Those physicians who favor the CREST results in news reports propose that the positive outcomes with stenting are dependent on a high surgical skill level. Those physicians who favor the ICSS results note that, in CREST, the risks of periprocedural stroke and the composite outcome of death, MI, or stroke at 30 days were significantly higher with stenting (4.3% vs 2.3% and 5.2% vs 4.5%, respectively). They also cite previous studies (ie, the EVA-3S and SPACE trials) that failed to show the short-term equivalence of stenting. 

Upcoming post-hoc analyses of CREST may aid the identification of subpopulations (eg, those younger than 70 years of age) who are likely to realize more positive outcomes with carotid stenting. These data may inform the preferential use of carotid stenting in practice—at least when the surgeon is skilled in the procedure.

N.B.--One notable and underreported finding from the ICSS MRI substudy is that, in patients who received stents, embolic protection devices (like the FiberNet EP System) were associated with significantly higher rates of stroke (73% vs 34%). In patients who underwent CEA, the stroke rates with and without embolic protection devices were 17% and 16%, respectively. 

EVA-3S = Endarterectomy Versus Angioplasty in Patients With Symptomatic Severe Carotid Stenosis; NINDS = National Institute of Neurological Disorders and Stroke; SPACE = Stent-Supported Percutaneous Angioplasty of the Carotid Artery Versus Endarterectomy.

Anatomic diagram of the common, internal, and external carotid arteries from Gray's Anatomy (1918).

05/27/10 addendum: Peer-reviewed results of CREST are now available in today's issue of the NEJM and tabulated here. Although there was no clinical advantage with endarterectomy for the estimated 4-year combined primary outcome, endarterectomy edged out stenting for several secondary outcomes.