ASTER final data confirm no difference between ADAPT and stent retriever as thrombectomy frontline strategy

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The final results of the ASTER randomised controlled trial have confirmed that there was no statistically significant difference between ADAPT (a direct aspiration first pass technique) and stent retriever as frontline mechanical thrombectomy strategies in the treatment of large vessel occlusion stroke.

The final data were presented by the study’s scientific coordinator, Bertrand Lapergue (Suresnes, France), at the European Stroke Organisation Conference (ESOC; 16–18 May, Prague, Czech Republic). Lapergue also presented the primary results earlier in the year at the International Stroke Conference (ISC; 22–24 February, Houston, USA).

The ASTER trial (Interest of a direct aspiration first pass technique [ADAPT] for thrombectomy revascularisation of large vessel occlusion in acute ischemic stroke) sought to determine what technique should be used as frontline strategy (ADAPT or stent retriever) to achieve maximum reperfusion. The study is a prospective, randomised, multicentre, controlled open-label design with blinded outcome evaluation.

Since the publication of five randomised controlled trials in 2015 which showed that favourable outcome is strongly associated with the successful reperfusion status (TICI 2b/3=71% with a stent retriever in the HERMES meta-analysis), mechanical thrombectomy with a stent retriever in association with IV t-PA is now the standard of care in anterior circulation ischaemic stroke caused by a large vessel occlusion.

Now other techniques exist, such as ADAPT, which seem very promising to increase reperfusion status and clinical outcome, but which have up to now only been tested in retrospective studies.

Lapergue explained that ADAPT is an easy technique because the aspiration catheter is trackable and the procedure is short. “You just have to advance your aspiration catheter until it is in contact with the clot and then you connect the aspiration catheter to a pump, wait, and aspirate the clot, and you can do it again if you cannot remove the clot. Further, it is a versatile technique because you can use your aspiration catheter to pass the stent retriever inside so that you can do both techniques if necessary—if operators fail with aspiration first, they can use a stent retriever inside the aspiration catheter for a combine technique of aspiration and stent retriever,” he said.

The objective of the ASTER trial was to answer the question: What technique should I choose in frontline strategy (ADAPT or stent retriever) to achieve maximum reperfusion?

The primary outcome was successful revascularisation (mTICI 2b/3) at the end of treatment. Secondary outcomes were successful revascularisation after the assigned treatment technique, procedural times, need for a rescue technique, complications and modified Rankin scale (mRS) at three months.

Patients were randomised to either ADAPT or stent retriever as the frontline strategy (the first three attempts). Over a 12-month period beginning October 2015, study investigators at eight centres in France randomised 381 patients; 189 were allocated to stent retriever with balloon-guide catheter (stent retriever first group) and 192 to the ADAPT technique (ADAPT first group).

In the stent retriever first group, 19 patients did not receive the allocated intervention: 12 had spontaneous clot lysis, one groin access failure, five protocol violations (ADAPT), and one extracranial stenting without stent retriever. In the ADAPT first group, 18 patients did not receive the allocated intervention: 15 had spontaneous clot lysis and three groin access failures.

In terms of baseline characteristics, in the stent retriever first group, patients were 68.1 (±14.6) years old, 55% male and had an average NIHSS score of 17. In the ADAPT first group, patients were 71.7 (±13.8) years old, 53.7% male and had an average NIHSS score of 18.

When it comes to time metrics, Lapergue pointed out that previous reports have shown that the ADAPT technique is associated with shorter procedure times than stent retriever. “When you focus only on the procedure, we showed the same thing—time from clot contact to reperfusion was a little bit shorter with the aspiration technique (13 minutes from clot contact to reperfusion in the ADAPT group versus 23 minutes in the stent retriever group),” he explained.

The key time metrics showed the following in the stent retriever first group and the ADAPT first group, respectively:  116 minutes versus 109 minutes from symptom onset to imaging; 119 minutes versus 107 minutes from imaging to groin puncture; 21 minutes versus 18 minutes from groin puncture to clot contact; and 23 minutes versus 13 minutes from clot contact to TICI 2b/3 reperfusion.

Primary outcome of core lab assessed reperfusion outcomes showed no significant difference between the two groups with 157 patients (83.1%) achieving TICI 2b/3 in the stent retriever first group, versus 164 patients (85.4%) in the ADAPT first group (p=0.53).

As it relates to adjunctive therapy, 45 patients (23.8%) in the stent retriever first arm required a change of strategy, versus 63 patients (32.8%) in the ADAPT first arm (p=0.053). Further, successful reperfusion after the first strategy was similar in both groups: stent retriever first saw 128 patients (67.7%) with TICI 2b/3 and 67 patients (35.4%) with TICI 3; while the ADAPT first group saw 121 patients (63%) with TICI 2b/3 and 55 patients (28.6%) with TICI 3.

When the mRS score was assessed at three months, Lapergue reported that no statistically significant difference was observed between the two groups. Similarly, as it relates to safety endpoints, including complications such as embolization into a new territory, arterial perforation, arterial dissection, vasospasm and intracranial haemorrhage, there was no difference between the two arms.

“The ASTER trial is the first independent large randomised controlled trial focused on the ADAPT technique with a blinded assessment. The ASTER trial showed no statistically significant difference between the two strategies as a frontline thrombectomy approach with similar efficacy and safety endpoints. I think we have opened the door to proposing new tools to remove the clot. Again, the success of the stent retriever was a huge advance, but the rate of TICI 3, which is a major factor in fighting the disability of our patients, is less than 50% with stent retriever and this was the same with aspiration. We have to do more, we have to develop and assess new strategies to increase the rate of perfect reperfusion in our patients,” Lapergue concluded.

The study was funded with an unrestricted research grant by Penumbra, but the sponsor was not involved in the study design, study conduct, protocol review or manuscript preparation and review.