The first randomised controlled trial (RCT) to directly compare the efficacy of the combined use of contact aspiration and stent retriever against a stent retriever alone has found no superiority for the former. “We detected an 8% difference in favour of the combined strategy, but it was not significant,” announced Bertrand Lapergue (Stroke Center, Hôpital Foch, Suresnes, France) while presenting data from the ASTER2 trial at the European Stroke Organisation Conference (ESOC; 22–24 May, Milan, Italy).
Speaking to the ESOC audience, Lapergue said that ASTER2 (Combined use of contact aspiration and the stent retriever technique versus stent retriever alone for recanalisation in acute cerebral infarction) was based on the strong relationship between recanalisation and disability. “The definition of successful recanalisation is thrombolysis in cerebral infarction (TICI) grade 2c/3, which is important to understand, because if you look at the rate of modified Rankin Scale (mRS) score 0–2 after TICI 2b compared to TICI 3, there is a huge difference in terms of disability.”
Moreover, given that a recent HERMES collaboration elicited a rate of modified TICI 2c/3 in 31.4% of patients, Lapergue argued that “this is not enough,” and suggested that there may be a potential benefit on recanalisation of a combined contact aspiration and stent retriever approach.
In a previous interview, Lapergue told NeuroNews, “The advantages of the combined stent-aspiration technique include the potential synergistic effect of the technique when used simultaneously, as well as the use of a flexible large-bore catheter in a triaxial system—which provides stability for the stent-retriever.”
He added, “Whatever the first-line strategy chosen by the interventionalist, the rate of TICI 2c/3 remains low. The choice of the first-line endovascular procedure is a critical issue given that the number of passes is correlated with higher per procedure complications and lower favourable outcome.”
In light of the latter, Lapergue and his team aimed to ascertain whether the combined used of contact aspiration and stent retriever is more efficient that stent retriever alone as a first-line endovascular treatment.
Carried out at 11 centres in France from October 2017 to May 2018, ASTER2 was a prospective, randomised, multicentre, open-label, blinded end-point clinical trial. Patients admitted with suspected anterior circulation ischaemic stroke secondary to large vessel occlusion, with onset of symptoms <8 hours, were randomly assigned to treatment with combined catheter aspiration and stent retriever, or stent retriever alone in a 1:1 ratio.
The primary outcome was the rate of “perfect reperfusion,” defined by a modified TICI score of 2c or 3 at the end of the endovascular procedure. Additionally, secondary outcomes include procedural outcomes, intracerebral haemorrhage at 24-hours, the modified Rankin Scale, as well as all-cause mortality at 90-days.
Using a two-sided test (alpha=5%, power=80%) while anticipating rate of spontaneous recanalisation and catheterisation failures of 20%, Lapergue and colleagues estimated that a sample size of 408 patients would be necessary to detect an absolute difference of 15% in primary outcome.
Regarding the results, Lapergue announced, “In terms of complete recanalisation at the end of treatment—we detected an 8% difference in favour of the combined strategy, but it was not significant.” Specifically, 131 patients (64.5%) in the combined strategy group achieved TICI 2c/3 and 117 (57.9%) patients in the stent retriever alone group achieved the same level of recanalisation (p=0.17).
In relation to safety, he posited, “There was no difference in safety concerns between the two harms, in terms of embolisation in a new territory, arterial perforation, arterial dissection and vasospasm. Even regarding symptomatic intracerebral haemorrhage, or new infarct.”
Delving further into the data, Lapergue said, “It was interesting because when we look at the pre-specified subgroup and at the ICA [internal carotid artery] occlusion… in this case there is a high burden of clot, and there is strong data supporting the combined approach. So in the future, we may adapt our strategy according to the site of occlusion or the type of clot.”
When further questioned on whether these data from subgroup analyses can support individualised treatment approaches during an ESO interview, he put forward, “We need more data on this, but the main result is that we do not support any maximalist [combined] approach for all patients… so whatever strategy is used, chose the one you trust.”
Shedding light on what the future holds following ASTER2, Lapergue surmised, “Probably, in the future, we will be able to detect a specific group, such as patients with ICA occlusion or according to the type of clot, and chose the type of endovascular therapy. The first thing is to increase the rate of complete recanalisation now using modern approaches. In the future, we could adapt the strategies to achieve complete recanalisation. I think there is a new area of research on this issue.”