Juan Carlos Martinez Gutierrez, MD
Langezaal LCM, van der Hoeven EJRJ, Mont’Alverne FJA, de Carvalho JJF, Lima FO, Dippel DWJ, van der Lugt A, Lo RTH, Boiten J, Lycklama À Nijeholt GJ, et al. Endovascular Therapy for Stroke Due to Basilar-Artery Occlusion. N Engl J Med. 2021:384:1910-1920.
Langezaal et al. published results on the BASICS study in the NEJM. This study was an international randomized open-label blinded outcome trial comparing standard medical management (MM) versus Endovascular Thrombectomy (EVT) for Basilar Artery Occlusions (BAO).
They recruited patients aged <85 years with BAO within 6 hours of symptoms onset, National Institutes of Health Stroke Scale score (NIHSS) >10, and no large established infarct (i.e., bilateral brainstem, cerebellar infarct with mass effect or hydrocephalus). The trial was initially powered to detect a 10% difference between arms based on available evidence from the BASICS registry, which showed favorable functional outcome (modified Rankin Score [mRS] 0-3) in 40% of participants treated with EVT and in 30% of those treated with MM. This initial design required 750 patients; however, after 4 years of slow recruitment and new evidence of EVT benefit in the anterior circulation, the trial was redesigned. The new assumption was that treatment effect may be higher based on the positive 2015 EVT trials, so the expected mRS 0-3 rate was increased to 46% for the EVT arm. The 16% risk reduction resulted in a smaller sample size estimation of 300. In addition, to increase potential recruitment, the eligibility criteria was expanded to include patients aged >85 years, those with NIHSS <10 and those with contraindications for intravenous thrombolysis.
Baseline was mostly balanced except greater prevalence of atrial fibrillation in the EVT group (28.6% vs 15.1%). Of note, baseline mean NIHSS was 22. Of the EVT treated patients, 72% achieved TICI2b-3, and 24-hour CTA showed 84.5% patency compared to 56.3% in the MM arm. Despite EVT procedure success, the primary outcome of mRS 0-3 was 44.2% in the EVT arm and 37.7% in the MM arm (RR 1.18, CI 0.92-1.50), not statistically different. However, in subgroup analyses, it was found that patients with NIHSS >10 had a larger treatment effect from EVT compared to MM. Safety outcomes were also not significantly different but there was a trend towards higher symptomatic intracranial hemorrhage (4.5 vs 0.7%) and higher brain edema (11 vs 4.8%) in the EVT group.
A few points to note: Eligibility was established with CT alone and not advanced imaging in an anatomical area where small infarcts can have large irreversible impact. Screening logs revealed that 98/124 (79%) patients not enrolled underwent EVT suggesting selection bias (also data on their outcome is not provided and could sway results significantly). There was a 4.8% crossover from MM to EVT compared to 1.9% in reverse. The medical arm did significantly better than expected. Importantly, midpoint redesign likely allowed for more recruitment of lower NIHSS cases which appear not to benefit from EVT. Taken together, the study has limitations, and benefit of EVT for BAO cannot be excluded. Nevertheless, given the lessons learned on the difficulty of conducting BAO trials and a dwindling equipoise, it is unclear if more randomized clinical trials should be pursued aside from the ongoing Basilar Artery Occlusion Chinese Endovascular Trial (BAOCHE). Thus, we are back to the basics of wide practice variability in BAOs.