MONTREAL – A randomized trial designed to definitively test the efficacy of mechanical thrombectomy for treating acute ischemic strokes caused by basilar artery occlusion fell victim to slow recruitment and crossovers that muddied the intention-to-treat results, but the per-protocol and as-treated analyses both showed that thrombectomy was superior to best medical therapy in a multicenter, randomized study with 131 Chinese patients.
“Our findings should be considered in the context of the best evidence currently available, and progressive loss of equipoise for endovascular therapy for severe, large-vessel occlusion strokes,”, said at the World Stroke Congress. “This was not a perfect trial, but it’s the best data we have, by far, at least for now” on the value of mechanical thrombectomy for treating acute ischemic stroke caused by a basilar artery occlusion, added Dr. Nogueira, professor of neurology and director of the neuroendovascular service at Emory University, Atlanta.
In the study’s per-protocol analysis, which considered patients who received their randomized treatment, the study’s primary endpoint of a modified Rankin Scale (mRS) score of 0-3 at 90 days after treatment was 44% in 63 patients who underwent thrombectomy and 26% in 51 patients randomized to best medical therapy who remained on that regimen, a statistically significant difference, Dr. Nogueira reported. In the as-treated analysis, which considered all enrolled patients based on the treatment they actually received regardless of randomization group, 77 patients treated with thrombectomy had a 47% rate of achieving the primary outcome, compared with 24% of 54 controls, also a statistically significant difference.
In contrast, the prespecified primary analysis for the study, the intention-to-treat analysis that considered patients based on their randomization assignment regardless of the treatment they actually received, showed that after 90 days the rate of patients with a mRS score of 0-3 was 42% in 66 thrombectomy patients and 32% among 65 controls, a difference that was not significant; this is a finding that, from a purist’s standpoint, makes the trial’s result neutral. The per-protocol and as-treated analyses were also prespecified steps in the study’s design, but not primary endpoints.
Despite the shortcoming for the primary analysis, Dr. Nogueira said that he found the per-protocol and as-treated findings very persuasive. “I personally could not randomize these patients” in the future to not receive mechanical thrombectomy, he confessed from the podium.
Thetrial randomized 131 patients at any of 28 Chinese sites between April 2015 and September 2017. Patients had to enter within 8 hours of stroke onset. The original trial design called for enrolling 344 patients, but the steering committee decided in 2017 to prematurely stop the study because of a progressive drop in enrollment of patients, and “excessive” crossovers from the control arm to thrombectomy, a total of 14 patients. During the final month of the trial, 6 of 10 patients assigned by randomization to receive best medical care instead underwent thrombectomy. “At that point, we pretty much had to stop,” Dr. Nogueira said. Enrolled patients averaged about 65 years old, about 90% had a basilar artery occlusion and about 10% a vertebral artery occlusion, about 30% received intravenous alteplase, and the median National Institutes of Health Stroke Scale score at entry was about 30.
The major adverse effect from thrombectomy seen in the study was symptomatic intracranial hemorrhage, which occurred in 5 of the 77 patients (6%) actually treated with thrombectomy, compared with none of the 54 patients not treated with thrombectomy. This modest rate of intracranial hemorrhages was “not unexpected,” Dr. Nogueira noted.
Acute ischemic strokes caused by a basilar artery occlusion are relatively uncommon, accounting for about 1% of all acute ischemic strokes and 5%-10% of acute ischemic strokes caused by occlusion of a proximal intracranial artery. But when these strokes occur, they are a “neurological catastrophe,” Dr. Nogueira said, causing severe disability or mortality in about 70% of patients.
BEST had no commercial funding. Dr. Nogueira reported no disclosures.
SOURCE: Nogueira RG et al. Int J Stroke. 2018;13(2_suppl):227, .