New research demonstrates the efficacy and safety of endovascular treatment for patients who were treated in the late window after experiencing an ischemic stroke caused by an anterior circulation large-vessel occlusion. The MR CLEAN-LATE trial – an open-label, blinded-endpoint, randomized, controlled, trial conducted in 18 stroke intervention centers in the Netherlands – included adults with ischemic stroke who presented 6-24 hours from symptom onset or last seen well with an anterior circulation large-vessel occlusion, collateral flow on CT angiography, and a neurological deficit score of at least 2 on the National Institutes of Health Stroke Scale. Patients were randomly assigned to receive endovascular treatment or no endovascular treatment, plus best medical treatment. Of the 535 patients who were randomly assigned, 94% gave deferred consent or died before consent was obtained (255 in the endovascular treatment group and 247 in the control group) and comprised the modified intention-to-treat population. At 90 days, the median modified Rankin Scale (mRS) score – the primary outcome – was 3 in the endovascular treatment group and 4 in the control group. Using the mRS, researchers noted a shift toward improved outcomes for the endovascular treatment group (adjust common OR 1.67). All-cause mortality was 24% (62 of 255 patients) in the endovascular treatment group and 30% (74 of 247 patients) in the control group. Rates of symptomatic intracranial hemorrhage in the two groups were 7% (17 patients) and 2% (4 patients), respectively. “Our results, in addition to previous literature, support that the selection of patients for endovascular treatment in the late window could be primarily based on the presence of collateral flow,” the researchers conclude.