New data from the VECTOR randomised controlled trial—presented at the European Stroke Organisation Conference (ESOC; 24–26 May, Munich, Germany)—have indicated that a mechanical thrombectomy in which a stent retriever is deployed alongside contact aspiration, a ‘combined technique’, is not significantly superior to contact aspiration alone, as per expanded thrombolysis in cerebral infarction (eTICI) 2c/3 after three passes. However, the study’s secondary outcomes appeared to indicate a greater benefit with the combined technique.
Delivering these findings, Romain Bourcier (Nantes University Hospital, Nantes, France) initially highlighted the current uncertainty over which of the multiple specific approaches to thrombectomy in acute ischaemic stroke patients can produce the best outcomes. The prospective, multicentre VECTOR study was designed to shed some light on this matter, evaluating if a first-line treatment strategy involving a combined strategy (Embotrap II/III stent retriever [Cerenovus] plus contact aspiration) could achieve better reperfusion outcomes compared to first-line contact aspiration alone.
The study included patients with an acute ischaemic stroke caused by red thrombi in the anterior circulation, identified via a positive susceptibility vessel sign on magnetic resonance imaging (MRI). Its objective, Bourcier detailed, was to demonstrate superiority with the combined technique—defined as a high grade of reperfusion (eTICI 2c/3)—over an aspiration-only approach. A total of 526 patients were randomised in VECTOR, with 263 being allocated to the combined-technique group and 258 receiving aspiration alone as their first-line treatment.
As per the trial’s primary efficacy outcome, a high reperfusion score after the assigned first-line approach—and prior to any subsequent secondary interventions—was achieved 57.8% of the time in the combined-technique group compared to 52.3% in the aspiration-only group. Bourcier noted that these effect sizes were calculated following adjustments for a number of variables, including centre, age, intravenous thrombolysis (IVT), occlusion site and general anaesthesia.
Secondary angiographic outcomes revealed significantly greater first-pass reperfusion rates with the combined technique versus aspiration alone, corresponding to an absolute increase of 11%. Additional assessments also found significant improvements in ≥eTICI 2b rates with the combined technique versus aspiration alone after the initial strategy—although there was no significant difference in eTICI 3 rates between groups. Reperfusion outcomes at the end of the entire endovascular procedure, i.e. following any necessary second-line interventions, were found to be broadly similar across the two groups, although ≥eTICI 2b, ≥eTICI 2c and eTICI 3 rates were all marginally higher in the cohort of patients who received first-line aspiration alone.
Bourcier went on to report “no difference” in functional outcomes between the two groups, signified by changes in mean 24-hour National Institutes of Health stroke scale (NIHSS) and three-month modified Rankin scale (mRS) scores. Finally, the speaker touched on safety outcomes seen in VECTOR, detailing comparable rates of embolisation in new territories (ENT) between groups, before noting an increased rate of 24-hour symptomatic intracranial haemorrhage (ICH) in the combined group (11.6%) versus the aspiration-only group (7.2%).
As such, despite a number of secondary analyses indicating improved reperfusion outcomes can be achieved by deploying a stent retriever alongside contact aspiration, the combined technique assessed in VECTOR ultimately demonstrated no superiority versus aspiration alone, as per the trial’s primary efficacy endpoint. Bourcier further remarked that questions remain regarding the most appropriate, clinically relevant angiographic endpoint through which to measure success in thrombectomy, and how specific clot types can impact procedural outcomes.
“We pave the way for future trials integrating an assessment of the occlusion type,” he added, concluding with a nod to future subgroup analyses of VECTOR, which plan to evaluate discrepancies between clot locations (internal carotid artery [ICA] versus middle cerebral artery [MCA]), and the effect of giving or withholding IVT alongside these different thrombectomy techniques.