ASTER RCT finds no significant difference between ADAPT and stent retriever as frontline strategy in acute stroke

Bertrand Lapergue

The primary results of the ASTER randomised controlled trial (RCT) have shown 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 (LVO) stroke.

Presented by Bertrand Lapergue (Suresnes, France) at the International Stroke Conference (ISC; 22–24 February, Houston, USA) the ASTER trial (Interest of direct aspiration first pass technique 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.

ADAPT is a novel technique which uses an atraumatic large bore aspiration catheter that is easily trackable.

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.

“That is good, but we think we need to increase the rate of successful reperfusion and perfect reperfusion (meaning TICI 3). Previous reports have shown reperfusion rates with ADAPT are very high, but we needed to do a randomised controlled trial to assess exactly the impact of aspiration versus stent retriever [as frontline strategy]. The question is should you start with aspiration or stent,” Lapergue said.

The primary outcome in the ASTER trial 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 there was no clear difference between the two strategies. “The only thing we saw was when you look at the delay between the clot contact to reperfusion, it is a little bit shorter with the aspiration technique,” he reported.

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 rescue 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.

“The ASTER trial is the first independent large randomised controlled trial focused on a new strategy comparing with it the gold standard. The ASTER trial showed no statistically significant difference between aspiration and stent retriever as a frontline thrombectomy approach with similar efficacy and safety endpoints,” Lapergue concluded.

Finally, he revealed that further subgroup analyses, clinical outcomes and cost-effectiveness analysis will be reported at the European Stroke Organisation Conference (ESOC; 16­–18 May, Prague, Czech Republic).

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.