Final results of the Basilar artery international cooperation study (BASICS) have been reported by Wouter J Schonewille (University Medical Centre Utrecht, Utrecht, the Netherlands) during a large clinical trials webinar hosted jointly by the European Stroke Organisation (ESO) and the World Stroke Organisation (WSO), on 13 May.
Concluding BASICS—which set out to assess the efficacy and safety of endovascular therapy (EVT) plus best medical management, versus best medical management alone, <6 hours of the estimated time of basilar artery occlusion (BAO), Schonewille said— “We found a limited risk difference of 6.5% after endovascular therapy in BAO, mainly due to a better than expected outcome after best medical management alone.”
However, though acknowledging that the trial was underpowered, he alluded to some interesting findings. “Endovascular therapy tended to be more effective in patients over 70 years than in younger patients. Most interesting, we found a significant difference in outcome favouring EVT in patients with moderate to severe stroke, or NIHSS [National Institutes of Health Stroke Scale] ≥10 or more, while there was a trend towards a better outcome after IV thrombolysis in patients with minor deficits, or NIHSS <10. There was also a signal that patients did better after EVT if they were pre-treated with IV thrombolysis.”
Schonewille also reported that EVT was “remarkably” safe, as only 4% of patients in the intervention arm had a symptomatic intracranial haemorrhage within three days of treatment (0.7% in the control arm). He also noted that mortality at 90 days was slightly lower in the EVT arm (38.2% vs. 43.2% for best medical management), but the difference was not significant.”
BASICS was a multicentre, international, controlled trial, with randomised treatment-group assignments, open-label treatment and blinded outcome assessment. Patients were assigned in a 1:1 ratio, stratified according to: randomising centre, use of IV thrombolysis and NIHSS score (<20 vs. ≥20).
Schonewille told viewers that the calculated sample size was 300 patients, assuming favourable outcome in 46% with EVT plus best medical management, and 30% with best medical management alone, giving an absolute risk reduction of 16%.
However, in the intervention arm, 44.2% had a favourable outcome as compared to 37.7% in the control arm, yielding an absolute risk reduction of 6.5%, which, according to Schonewille, was “considerably lower” than the expected risk reduction calculated of 16%.
Of the 300 randomised patients, 154 were randomised to the intervention arm, and 146 received best medical management alone (the control arm). No patients were lost to follow-up at three months. “The demographics were well balanced, with the average age around 67 in both arms. Close to 80% of patients were treated with IV thrombolysis, and the median NIHSS score was just above 20 in both treatment arms,” Schonewille said.
In terms of the secondary outcomes, the BASICS collaborators did not find a significant difference in excellent outcome (mRS 0–2), at day 90, as there was only an absolute risk reduction of 5%. Additionally, no significant difference in modified Rankin Scale scores on shift analysis was observed.
The inclusion criteria Schonewille highlighted were: EVT had to be feasible within six hours of estimated time of BAO, and if indicated, IV thrombolysis had to be started within 4.5 hours of BAO. In contrast, patients were excluded if they had intracranial haemorrhage, extensive brainstem ischaemia, and cerebellar mass effect or acute hydrocephalus.
He also acknowledged that the team, during their interim analyses, used sequential monitoring with a triangular test, each with 25 patients included. On the last interim analysis (n=252), the Data Safety Monitoring Board (DSMB) recommended continuing the trial to completion (n=300).”
Most patients were randomised in the Netherlands (n=200), followed by Brazil (n=42), Germany (n=31), France (n=12), Italy (n=10), Switzerland (n=4), and Czech Republic (n=1).