BASICS: Endovascular Therapy Adds Little for BAO Stroke

Endovascular therapy adminstered in conjunction with best medical management for basilar artery occlusion (BAO) stroke did not significantly improve functional outcome at 90 days compared to best medical management alone, a randomized, multicenter trial suggests.

Of the participants who were randomly assigned to receive endovascular therapy (EVT) along with best medical management (BMM), 44% experienced a favorable functional outcome, compared to 38% of the BMM-only control group.

"We did not find a significant difference in outcome in favor of endovascular therapy," Wouter Schonewille, MD, PhD, said May 13 during a clinical trials webinar of the ESO-WSO 2020 Congress, sponsored by the European Stroke Organization and the World Stroke Organization

Schonewille and colleagues had predicted that adding EVT would confer at least a 16% relative risk reduction.

However, results showed an absolute risk reduction of only 6.5% associated with the addition of EVT, "mainly due to a better than expected outcome in the control group," added Schonewille, a neurologist at the University Medical Center Utrecht and Rudolf Magnus Institute of Neurosciences and the St. Antonius Hospital, Nieuwegein, the Netherlands.

Conflicting Reports

The lack of significant benefit associated with EVT in the current Basilar Artery International Cooperation Study (BASICS) emerges in stark contrast to results of the EVT for Acute Basilar Artery Occlusion Study (BASILAR) registry analysis,, announced in February 2020, in which a statistically significantly higher proportion of people treated with EVT and thrombolysis achieved functional improvement at 90 days.

Researchers observed this outcome in 32% of the dual intervention group, compared with 9% of the thrombolysis-only group, as previously reported by Medscape Medical News.

Furthermore, prior trials pointed to "overwhelming evidence of efficacy" of EVT for anterior circulation strokes, Schonewille said, but he noted that results are less clear concerning posterior circulation events such as BAOs.

To learn more, Schonewille and colleagues enrolled 300 adults in the BASICS study between October 2011 and December 2019 in the Netherlands, Brazil, Germany, Italy, Norway, and Switzerland.

They randomly assigned 154 participants to dual therapy and another 146 to BMM alone. Therapy was given within 6 hours of estimated time of BAO onset. Approximately 80% of participants in each group received intravenous thrombolysis, which needed to be administered within 4.5 hours of stroke onset.

The average age of the patients was 67 years; 35% of participants were women. The National Institutes of Health Stroke Scale (NIHSS) score "was just above 20 in both arms," Schonewille said. Medical history was well balanced between arms except that atrial fibrillation was more prevalent in the EVT plus BMM group.

The primary outcome, functional outcomes at 90 days, was based on a modified Rankin scale (mRS) of 3 or less. The risk ratio was 1.18 (range, 0.92 – 1.50).

The researchers did not find a significant difference in the secondary outcome of "excellent outcome" either, at 35% vs 30%. That outcome was defined as an mRS score of 0 to 2 at 90 days.

Safety Outcomes

"Endovascular therapy was remarkably safe," Schonewille said.

The occurrence of symptomatic intracranial hemorrhage (sICH) within 3 days was noted in 3.9% in the EVT group, vs 0.7% in the BMM arm.

Mortality at 90 days was slightly lower in the endovascular arm, at 38%, compared to 43% in the BMM group after adjustment for differences in atrial fibrillation. The rates were not statistically significantly different.

A Kaplan-Meier curve "shows most deaths occurred in the first few days," he added.

"Our trial was underpowered to show a statistically significant benefit of endovascular therapy in patients treated within 6 hours of BAO," Schonewille said.

Although he urged caution in interpreting subgroup analyses in this study because it was underpowered, "there are some interesting findings."

Subgroup analyses suggest a significant benefit of EVT for patients with a severe stroke, defined as an NIHSS of 10 or greater. In addition, the treatment effect of EVT compared to BMM appeared slightly stronger in patients aged 70 years or older compared to younger patients.

"Best medical management might be the best treatment option in patients with a mild deficit or an NIHSS less than 10," he added.

Further Clarification Needed

"This is a very difficult area to study. The two best trials we have ― BEST and BASICS ― suggest benefit but did not reach statistical significance," webinar moderator Jesse Dawson, MD, told Medscape Medical News when asked to comment.

"Both trials suggest there could be clinically important benefits, but BEST was limited by crossover to intervention in control patients ― and both trials were relatively small," added Dawson, professor of stroke medicine at the University of Glasgow and consultant physician at Queen Elizabeth University Hospital in Scotland.

At present, best medical treatment and mechanical thrombectomy "are viable options for patients with basilar artery occlusion, and clinicians should continue to offer individualized care for their patients, dependent on the specifics of each case," Dawson said.

"Hopefully," he added, a pooled analysis of data in the future will "give further clarity."

"Somewhat Surprising" Results

"The findings of the BASICS trial are somewhat surprising, mostly when we considered the strong treatment benefit seen in the BEST trial per-protocol and as-treated analyses, as well as the equally large treatment benefit of the large BASILAR Registry ― which included a propensity score matching analysis," Raul Gomes Nogueira, MD, PhD, a lead author of the BASILAR trial, told Medscape Medical News when asked to comment.

Nogueira said there are multiple possible explanations for the BASIC results. "BASICS struggled with poor enrollment and became the longest acute stroke trial ever conducted ― over 8 years to be concluded." This duration of enrollment "suggests the possibility of treatment outside the trial and large selection bias."

Device technology and treatment technique evolved over those 8 years, and inclusion of patients with stroke of mild severity likely diluted the study's treatment effect, added Nogueira, who is affiliated with the Marcus Stroke and Neuroscience Center, Grady Memorial Hospital, Emory University School of Medicine, in Atlanta, Georgia.

Despite the potential limitations, Nogueira remained positive. "It will be beneficial to dissect the different patient subgroups in a pooled analysis of the BASICS and BEST trials in order to better understand the overall data. This is planned and should happen in the near future," he added.

"In my opinion...the value of BASICS is on the safety and probable benefit of this optimized IV thrombolysis regimen rather than questioning the irrefutable value of thrombectomy on large-vessel occlusions.

"The overwhelming evidence points to a dismal natural history for BAO with high clinical severity," Nogueira concluded. "These patients should continue to be treated aggressively, as supported by the subgroup analyses of both BASICS and BEST randomized controlled trials."

The BASICS trial was funded by the St. Antonius Hospital, the Dutch Heart Foundation, and the Swiss Heart Foundation. Schonewille and Dawson have disclosed no relevant financial relationships.

ESO-WSO 2020 Congress. Presented online May 13, 2020.

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