Research in context
Evidence before the study
Evidence to support endovascular therapy for stroke has previously been poor because randomised trials have used thrombectomy devices of low efficacy, insufficiently robust imaging selection criteria, and had long delays from hospital presentation to reperfusion. Five individual trials published in 2015 established that thrombectomy, when done with newer generation devices (mainly stent retrievers), more stringent imaging selection criteria, and more efficient workflow, significantly reduces disability rates after acute ischaemic stroke caused by proximal occlusion of large vessels in the anterior circulation. Because most of these studies were stopped prematurely, they were underpowered to provide convincing evidence of efficacy across some of the subgroups of great relevance to clinical practice. We did an extensive literature search of major online databases including PubMed and Embase for papers published from Jan 1, 2010, to Dec 23, 2015, and did not identify any other published randomised endovascular stroke studies that used modern thrombectomy devices. Study level meta-analyses have been reported but most included patients enrolled without definitive proof of vessel occlusion and who were treated with less effective reperfusion technology. Furthermore, study-level meta-analyses are considered less informative than patient-level meta-analytical approaches due to their inability to adjust for confounding baseline variables, which leads to less precise estimates of treatment effect. To our knowledge no patient-level meta-analyses have been reported.
Added value of this study
In this individual patient meta-analysis of trials published in 2015, we provide additional relevant facts that will enable clinicians to better understand the degree of precision of adjusted effect size estimates, safety outcome estimates, and estimates by clinical subgroups. We show clinical benefits for thrombectomy across a wide range of age and initial stroke severity and for patients eligible and ineligible for intravenous alteplase. Smaller amounts of other baseline variables such as degree of early ischaemic changes on baseline CT or time to treatment were reported and therefore the observed effects should be interpreted within the context of the populations included.
Implications of all the available evidence
The consistent results across different patient populations suggest that benefit from thrombectomy is generalisable to a broad range of patients with large-vessel ischaemic stroke. By providing a more precise treatment effect estimate than each individual trial, our findings allow cost-effectiveness of this intervention at society level to be calculated with higher precision. Our study provides clear evidence that in clinical practice, endovascular therapy for stroke should not be withheld on the basis of advanced age, moderately extensive early ischaemic changes on baseline CT, and moderate or severe clinical deficit.