EC-IC bypass surgery addition to medical therapy may not lower stroke risk in symptomatic artery occlusion

Supplementing medical therapy with extracranial-intracranial (EC-IC) bypass surgery does not alter the outcomes of stroke or death in patients with symptomatic ICA or MCA occlusion and hemodynamic insufficiency. No significant change was noticed in the composite outcome of stroke or death in the first 30 days or ipsilateral ischemic stroke beyond 30 days through 2 years.

The trial results were published in the journal JAMA on August 22/29, 2023. 

The main aim of extracranial-intracranial (EC-IC) bypass surgery is to restore blood flow by reducing the stroke risk and it is probably one of the treatment strategies for patients with hemodynamically compromised ICA or MCA occlusion. However, due to meager benefits, the trials were criticized owing to the type of patients selected who might benefit from such surgery. The earlier Carotid Occlusion Surgery Study (COSS) study resulted in a reduction in reduction in the EC-IC bypasses performed for symptomatic artery occlusion. But later the Carotid and Middle Cerebral Artery Occlusion Surgery Study (CMOSS) was designed to compare the EC-IC bypass surgery plus medical therapy with medical therapy alone in symptomatic patients with ICA or MCA occlusion and hemodynamic insufficiency, with refined patient and operator selection.

CMOSS was a randomized, open-label, outcome assessor–blinded trial conducted at 13 centers in China. A total of 324 patients with ICA or MCA occlusion with a transient ischemic attack or non-disabling ischemic stroke attributed to hemodynamic insufficiency based on computed tomography perfusion imaging were recruited between June 2013 and March 2018 and followed till March, 2020. Patients were randomized to surgery plus medical therapy (surgical group; n = 161) or medical therapy alone (medical group; n = 163). Medical therapy included antiplatelet therapy and stroke risk factor control.

The primary outcome measured was a composite of stroke or death within 30 days or ipsilateral ischemic stroke beyond 30 days through 2 years after randomization. Nearly 9 secondary outcomes were also assessed, including any stroke or death within 2 years and fatal stroke within 2 years.

Key findings:

• About 324 eligible patients with a median age of 52.7 years participated. There were 257 men [79.3%]), Out of the total 309 (95.4%) completed the trial.
• There was no significant difference found between the surgical group vs medical group for the composite primary outcome (8.6% vs. 12.3%).
• The 30-day risk of stroke or death was 6.2% (10/161) in the surgical group and 1.8% (3/163) in the medical group, and the risk of ipsilateral ischemic stroke beyond 30 days through 2 years was 2.0% (3/151) and 10.3% (16/155), respectively.
• Of the 9 prespecified secondary endpoints, none showed a significant difference including any stroke or death within 2 years (9.9% vs 15.3%) and fatal stroke within 2 years (2.0% vs 0%).

Thus, the findings from this trial did not support the addition of EC-IC bypass surgery to medical therapy for the treatment of patients with symptomatic atherosclerotic occlusion of the ICA or MCA.

Further reading: Ma Y, Wang T, Wang H, et al. Extracranial-Intracranial Bypass and Risk of Stroke and Death in Patients With Symptomatic Artery Occlusion: The CMOSS Randomized Clinical Trial. JAMA. 2023;330(8):704–714. doi:10.1001/jama.2023.13390