EU, U.S. CAS trial results differ due to various factors

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An analysis of randomized trials that evaluated outcomes of carotid artery stenting (CAS) and carotid endarterectomy (CEA) revealed several differences in ascertainment of MI and operator experience between studies that took place in the U.S. and Europe. William A. Gray, of Columbia University Medical Center in New York City, said that these differences may explain the worse outcomes seen in European studies and that these results “provide a cautionary perspective regarding studying early phase technology before it has had a chance to fully evolve.

“There are generic as well as carotid-specific trial design considerations that have the potential to materially affect the outcomes and interpretation of comparative studies between carotid artery stenting and carotid endarterectomy," wrote Gray, in a Vascular Medicine and Endovascular Intervention update published in the July issue of Progress in Cardiovascular Diseases, by Elsevier.

Gray said that the European trials that have been conducted have allowed “an imbalance in operator experience between stenting and surgery and have consistently allowed stenting procedures without embolic protection.” Operator inexperience and lack of embolic protection could be the culprit as to why these studies had such negative stenting results.

However, Gray noted that the U.S. and Canadian CREST (Carotid Revascularization with Endarterectomy vs. Stenting Trial) managed to avoid both of these aforementioned problems and its non-inferior results led to the FDA approval of a stent and protection for CAS for average-risk symptomatic and asymptomatic patients.

“Before considering the available data comparing CAS with CEA, several important features must be defined,” Gray offered. During the review, Gray only considered trials where embolic protection devices (EPDs) were used and all trials that evaluated patients at standard of usual risk for CEA were included.

Gray offered that while the French EVA-3S (Endarterectomy Versus Stenting in Patients with Symptomatic Severe Carotid Stenosis) trial was the first attempt to assess the safety and efficacy of CAS in standard risk patients, it fell short because of its lack of operating experience in the trial and issues surrounding ascertainment of MI.

In comparison, the CREST trial mandated the usage of EPDs and therefore the rate of EPD use during the study was greater than 98 percent. Gray said that “given that EPD use was mandatory, CREST is more representative of modern era CAS technique than any other study.” Additionally, CAS operators also underwent a rigorous qualifying process.

“The CREST embodies the state of the art in CAS vs. CEA trial design, with high EPD use, routine MI ascertainment, independent neurologic examination, and equivalent operator experience at the time the trial was performed,” Gray offered.

He said that the European studies suffered from “one or more major deficits” and said that their compromised results cannot represent the comparative state of CEA and CAS.

However, he offered that “In almost every sense, from the availability of operators with significant experience to availability and expertise with EPD through patient selection, if these trials were repeated today, it is likely their results would be much more similar than different.

Gray concluded that CAS and CEA should be tailored to each individual patient.