NEW YORK (Reuters Health) – Extracranial-intracranial (EC-IC) bypass surgery provides no added benefit over best medical therapy for preventing recurrent stroke in patients with symptomatic atherosclerotic internal carotid artery occlusion (AICAO) and hemodynamic cerebral ischemia, according to results of a study.

“Despite excellent graft patency and improved hemodynamics in the surgical group, EC-IC bypass surgery failed to provide an overall benefit on 2-year stroke recurrence,” the Carotid Occlusion Surgery Study (COSS) investigators report November 9 in the Journal of the American Medical Association (JAMA).

AICAO causes about 10% of transient ischemic attacks (TIAs) and 15% to 25% of ischemic strokes in the carotid territory, Dr. William J. Powers, of University of North Carolina School of Medicine, Chapel Hill, and colleagues note in their paper. “The 2-year risk of subsequent ipsilateral ischemic stroke while a patient receives medical therapy is 10% to 15%,” they say.

EC-IC was developed to prevent repeat stroke by improving hemodynamics distal to the occluded artery. The surgery entails connecting a branch of the external carotid artery (usually the superficial temporal artery) to a branch of the internal carotid artery (usually the middle cerebral artery), either directly or via a vein graft. The indications for EC-IC bypass are severe stenosis or occlusion of intracranial arteries with focal neurological symptoms, such as weakness or speech difficulties.

While EC-IC bypass has been available as a potential treatment for ischemic stroke for the past three decades, there has been considerable controversy surrounding the procedure due, in large part, to a study published in 1985 that failed to demonstrate benefit.

However, this study was “criticized for failing to identify the subgroup of patients with hemodynamic cerebral ischemia due to poor collateral circulation for whom surgical revascularization might be of greatest benefit,” Dr. Powers and colleagues note in their paper.

The COSS study was performed at 49 clinical centers in the United States and Canada. It enrolled 195 patients with recently symptomatic AICAO and hemodynamic cerebral ischemia identified by positron emission tomography (PET); 97 were randomized to receive surgery and 98 to no surgery. All received “best medical therapy” including antithrombotic therapy and risk factor intervention.

The trial was terminated early due to futility, the investigators report; rates of stroke or death at 2 years were similar in the surgery and non-surgery groups. The rates were 21.0% (20 events) and 22.7% (20 events), respectively, a difference of 1.7%.

At 30 days, rates of ipsilateral ischemic stroke were 14.4% (14 of 97) with surgery and 2.0% (2 of 98) without, a difference of 12.4%.

The investigators say the lower stroke risk in the nonsurgical group mirrors “better outcomes observed in more recent studies of patients with medically treated asymptomatic carotid artery stenosis, ascribed to improvements in medical therapy.”

Even though hemodynamics often improved with surgery, “better-than-expected efficacy of medical therapy in the nonsurgical group was sufficient to nullify any overall benefit of surgery,” the investigators report.

Dr. Joseph P. Broderick, of the University of Cincinnati College of Medicine, and Dr. Philip M. Meyers, of Columbia University, New York, co-authored a commentary published with the COSS results. It’s titled “Acute Stroke Therapy at the Crossroads.”

They make the point that “clinical decision making is based on a mix of scientific data, experience, training, and other influences, such as reimbursement, allure of new technology, current opinion, and bias.”

“Acute ischemic stroke care,” Drs. Broderick and Meyers write, “has reached a critical juncture: clinical practice, particularly the use of endovascular therapy, is starting down a road containing little scientific evidence of clinical efficacy, while the conduct of clinical trials to provide such critical data is impeded.”

“Physicians who provide care for patients with stroke must recognize the current lack of evidence for clinical efficacy of endovascular therapy and enroll patients in randomized trials,” they say.

SOURCE: JAMA 2011;306:1983-1992,2026-2027.