Elena Zapata-Arriaza, MD

Liu X, Dai Q, Ye R, Zi W, Liu Y, Wang H, et al. Endovascular treatment versus standard medical treatment for vertebrobasilar artery occlusion (BEST): an open-label, randomised controlled trial. Lancet Neurol. 2020;19:115-122.

Efficacy and safety of endovascular treatment (EVT) in anterior circulation strokes is clearly validated; however, such evidence is still lacking in vertebrobasilar occlusions. Liu et al. aimed to demonstrate safety and efficacy of EVT in posterior circulation strokes. To achieve this goal, the authors performed a multicenter, randomized, open-label trial in patients within 8 h of vertebrobasilar occlusion (basilar or V4 segment of vertebral artery). Patients were allocated to receive either EVT plus standard medical therapy or standard medical therapy alone. Given endovascular procedure, stent-retriever was the most employed technique, but thromboaspiration, intra-arterial thrombolysis, balloon angioplasty or stenting were also permitted. Primary outcome was mRS 0-3 at 90 days, assessed on an intention-to-treat basis. Primary safety outcome was mortality at 90 days. Secondary safety endpoints included symptomatic intracranial hemorrhage, device-related complications and other severe events rates. Each participating center had to have completed at least 5 mechanical thrombectomy procedures with stent retriever devices in the preceding year. The primary data analysis was done on the intention-to-treat population. In addition, secondary prespecified analyses were performed in the per-protocol population and in the as-treated population.

A total of 131 patients were enrolled and randomly assigned to the intervention group (N=66) or control group (N=65). However, the study was terminated prematurely because of excessive crossovers (22% in the control group) and poor recruitment. In the intention-to-treat analysis, there was no evidence of a difference in the proportion of participants with mRS 0-3 at 90 days according to treatment. Secondary prespecified analyses of the primary outcome, done to assess the effect of crossovers, showed higher rates of mRS 0-3 at 90 days in patients who actually received the intervention compared with those who received standard medical therapy alone in both per-protocol and as-treated. The 90-day mortality was similar between groups despite a numerically higher prevalence of symptomatic intracranial hemorrhage in the intervention group.

Following the path of  thrombectomy results in the anterior circulation strokes, its application in vertebrobasilar occlusions seems to be the logical evolution. However, we again have a study that does not show a clear benefit of thrombectomy compared to the best medical treatment. Increasing evidence on the efficacy of endovascular treatment in large vessel occlusion, and the poor prognosis of basilar occlusions without reperfusion, clearly makes randomization difficult, causing a high crossover rate that limits the final results. It is possible that these difficulties impact future studies with the same aim in the posterior circulation strokes, because clinicians may find it difficult to offer a therapeutic option (medical treatment) whose recanalization and, therefore, clinical outcome is worse. However, in order to obtain sufficient evidence to equate anterior and posterior circulation strokes, studies like this one are necessary, in order to reliably demonstrate what has been found in meta-analysis or registries like BASICS.

One limitation of this study could be the need to have completed only 5 thrombectomies with stentriever in the preceding year; this could be insufficient for the technical experience of the interventionist team, and which could further affect the recanalization rates and the final results. Likewise, the need for stent implantation in 20 patients (26%) is striking, which may be related to the higher rates of intracranial atheromatosis of the Asian population. This intracranial atheromatosis is associated with worse recanalization results and more functional dependence at 3 months, which would affect the conclusions of the study. In short, this study can be taken as a starting point for updated evidence, but there are still limitations that should be resolved in future trials.