ASTER
(2017)Objective
To compare efficacy and adverse events of first-line contact aspiration vs stent retriever technique for successful revascularization in patients with acute ischemic stroke and large vessel occlusion
Study Summary
• Contact aspiration was not superior to stent retriever for achieving successful revascularization (85.4% vs 83.1%, OR 1.20, P=0.53)
• No significant differences in functional independence at 90 days (45.3% vs 50.0%)
• Similar safety profiles with no significant differences in symptomatic ICH or mortality
• No significant differences in functional independence at 90 days (45.3% vs 50.0%)
• Similar safety profiles with no significant differences in symptomatic ICH or mortality
Intervention
First-line contact aspiration (ADAPT technique) vs first-line stent retriever thrombectomy
Inclusion Criteria
Adults with acute ischemic stroke due to anterior circulation occlusion (ICA, M1, or M2) within 6 hours of symptom onset
Study Design
Arms: Contact aspiration vs Stent retriever
Patients per Arm: 192 contact aspiration, 189 stent retriever
Outcome
• Primary: Successful revascularization (mTICI 2b/3) - 85.4% vs 83.1% (OR 1.20, 95% CI 0.68-2.10, P=0.53)
• Functional independence (mRS ≤2) at 90 days: 45.3% vs 50.0% (P=0.38)
• All-cause mortality at 90 days: 19.3% vs 19.2%
• Functional independence (mRS ≤2) at 90 days: 45.3% vs 50.0% (P=0.38)
• All-cause mortality at 90 days: 19.3% vs 19.2%
Bottom Line
First-line contact aspiration did not result in increased successful revascularization compared with first-line use of a stent retriever. No significant differences were found in clinical outcomes or adverse events.
Major Points
- First multicenter RCT comparing contact aspiration (ADAPT technique) vs stent retriever as first-line thrombectomy technique — 381 patients at 8 French neurointerventional centers.
- Primary endpoint (successful revascularization, mTICI 2b/3) was similar: 85.4% aspiration vs 83.1% stent retriever (OR 1.20, 95% CI 0.68–2.10, P=0.53) — no superiority of aspiration.
- No significant difference in functional independence at 90 days (45.3% aspiration vs 50.0% stent retriever) — clinical outcomes were equivalent between techniques.
- Aspiration showed a trend toward faster procedure time (38 vs 45 min puncture-to-revascularization, P=0.10) but required more rescue therapy (32.8% vs 23.8%, P=0.05).
- Similar safety profiles: sICH 5.3% vs 6.5%, mortality 15.4% vs 11.5% — no significant differences in any adverse event category.
- Established clinical equipoise between the two main thrombectomy approaches — operators can choose based on anatomy, clot characteristics, and personal expertise.
- Higher rescue therapy rate in aspiration group suggests first-pass aspiration alone is less reliable, but allowing rescue makes the overall approach equivalent.
- Confirmed by subsequent ASTER-2 (2021, aspiration vs combined approach) and COMPASS (2019, aspiration vs stent retriever) — consistent finding of technique equivalence.
- All centers had high expertise in both techniques — results may not apply to centers where operators are more experienced with one approach over the other.
- Powered for superiority (15% absolute difference) — the trial cannot exclude smaller but clinically meaningful differences between techniques, nor prove noninferiority.
Study Design
- Study Type
- Randomized, multicenter, open-label, blinded end-point clinical trial
- Randomization
- Yes
- Blinding
- Open-label, blinded endpoint assessment (PROBE)
- Sample Size
- 381
- Follow-up
- 90 days
- Centers
- 8
- Countries
- France
Primary Outcome
Definition: Successful revascularization (mTICI 2b/3)
| Control | Intervention | HR/OR | P-value |
|---|---|---|---|
| 83.1% (stent retriever) | 85.4% (aspiration) | 1.2 (0.68-2.10) | 0.53 |
Limitations & Criticisms
- Primary endpoint was technical (revascularization) rather than clinical (90-day mRS)
- Superiority design powered to detect 15% difference; not designed for noninferiority or equivalence
- Cannot exclude smaller but clinically significant difference between groups
- Rescue therapy at operator discretion is potential source of bias
- All participating centers highly experienced in both techniques; may limit generalizability
- Degree of randomness limited by stratified permuted randomization with fixed blocks of 4
- Not powered for subgroup analyses
- Open-label design with only endpoint blinding
- 24-hour NIHSS assessed by unblinded treating physician