PDF: BASICS
(2021)Objective
To evaluate the efficacy and safety of endovascular therapy compared with standard medical therapy in patients with acute basilar-artery occlusion within 6 hours of symptom onset.
Study Summary
• Symptomatic intracranial hemorrhage was more frequent in the thrombectomy group.
• Trial may have been underpowered; a potential benefit of thrombectomy could not be excluded.
Intervention
Multicenter, open-label, randomized controlled trial. Patients with acute basilar-artery occlusion were assigned within 6 hours to either endovascular therapy (± IV thrombolysis) or standard medical care (usually IV thrombolysis).
Inclusion Criteria
Adults with basilar-artery occlusion confirmed on CTA/MRA, presenting within 6 hours. Initial criteria: age <85 years and NIHSS ≥10; after 91 patients, expanded to allow age ≥85, NIHSS <10, and contraindications to IV tPA. Exclusions: intracranial hemorrhage; extensive, bilateral brainstem infarction on CT; cerebellar mass effect; or acute hydrocephalus.
Study Design
Arms: Endovascular Therapy vs. Medical Therapy
Patients per Arm: Endovascular: 154; Medical: 146
Outcome
• mRS 0–2: 35.1% vs. 30.1%; RR 1.17 (95% CI, 0.87–1.57)
• 90-day mortality: 38.3% vs. 43.2%; RR 0.87 (95% CI, 0.68–1.12)
• Symptomatic ICH: 4.5% vs. 0.7%
• Basilar artery patency at 24h: 84.5% vs. 56.3%
Bottom Line
Endovascular therapy did not significantly improve favorable functional outcomes (mRS 0-3) compared with medical therapy in basilar-artery occlusion (44.2% vs 37.7%; RR 1.18; 95% CI 0.92-1.50; P=0.19). Sample size was revised downward from an initial 750 to 300 patients due to slow enrollment over 8 years; the wide CI could not exclude a 10 percentage-point benefit, though a 16 percentage-point benefit was excluded under the revised assumptions. sICH was 4.5% vs 0.7% (P=0.06).
Major Points
- No significant benefit of EVT: favorable outcome (mRS 0-3) was 44.2% (EVT) vs 37.7% (medical), RR 1.18 (95% CI 0.92-1.50; P=0.19), a 6.5 percentage-point difference.
- Sample-size target was revised from the original 750 down to 300 patients due to slow enrollment; the final 300 patients were accrued over 8 years across 23 centers in 7 countries.
- Borderline higher sICH with EVT: 4.5% vs 0.7% (RR 6.9; 95% CI 0.9-53.0; P=0.06).
- No mortality difference: 38.3% (EVT) vs 43.2% (medical) (RR 0.87; 95% CI 0.68-1.12; P=0.29).
- EVT improved vessel recanalization: basilar patency at 24h was 84.5% vs 56.3% (RR 1.43; 95% CI 1.18-1.74). No formal significance testing was done for secondary outcomes (no prespecified plan for multiple-comparison adjustment).
- Moderate-severity NIHSS 10-19 showed signal of benefit: RR 1.55 (95% CI 1.06-2.27); 74% vs 47% favorable. Mild NIHSS <10 trended toward better with medical care (65% vs 80%).
- High IV tPA rate in both arms (~79%) likely contributed to 56.3% spontaneous recanalization, reducing incremental EVT benefit.
- Successful reperfusion (mTICI 2b/3) only 72% despite 94% use of 2nd/3rd-generation devices.
- Malignant brain edema numerically more with EVT: 11.0% vs 4.8% (RR 2.31; 95% CI 0.95-5.62; P=0.06).
- Results could not exclude a clinically meaningful benefit under the original 10 percentage-point assumption (upper CI of RR 1.50), but a 16 percentage-point benefit was excluded under the revised assumptions. Set the stage for BAOCHE.
Study Design
- Study Type
- Multicenter, open-label, international, randomized, controlled trial with blinded outcome assessment (PROBE design)
- Randomization
- Yes
- Blinding
- Open-label treatment; blinded outcome assessment for mRS; independent imaging core lab of 6 neuroradiologists. Permuted blocks (size 2), stratified by center, IV tPA use, and NIHSS (<20 or ≥20).
- Sample Size
- 300
- Follow-up
- 90 days (no patients lost to follow-up)
- Centers
- 23
- Countries
- Netherlands, Brazil, Germany, France, Italy, Switzerland, United States
Primary Outcome
Definition: mRS 0-3 at 90 days
| Control | Intervention | HR/OR | P-value |
|---|---|---|---|
| 55/146 (37.7%) | 68/154 (44.2%) | - (0.92-1.50) | 0.19 |
Limitations & Criticisms
- Underpowered relative to original plan: enrollment target was revised downward from 750 to 300 patients due to slow accrual over 8 years; wide CI does not exclude a 10 percentage-point benefit (though the revised 16 percentage-point threshold was excluded).
- 29.2% of eligible patients (124/424) treated outside trial; 79% of those received EVT — equipoise lacking among treating physicians.
- AF imbalance: 28.6% EVT vs 15.1% medical (adjustment did not substantially change results).
- Crossover: 4.8% of medical patients received EVT.
- No advanced imaging (CT perfusion) for patient selection.
- NIHSS less sensitive for posterior circulation symptoms.
- 8-year enrollment span — device technology and medical care evolved significantly.
- High IV tPA rate (~79%) in both arms may have attenuated the treatment effect.
- Successful reperfusion only 72% — lower than anterior circulation trials.
- Open-label design, though outcome assessment was blinded.
Citation
N Engl J Med 2021;384:1910-20.