BASILAR: Endovascular Treatment Improves Outcomes in BAO Stroke

Damian McNamara

February 21, 2020

LOS ANGELES — Endovascular therapy significantly improved functional outcomes and reduced mortality at 90 days compared with standard thrombolysis alone, new evidence from a large, prospective registry study suggests.

Participants who received both interventions were almost five times more likely to be able to walk independently at 90 days compared with those who received thrombolysis alone.

Despite multiple trials supporting the potential benefits of endovascular therapy for anterior stroke, little prospective research addresses outcomes associated with an ischemic stroke caused by a posterior basilar artery occlusion (BAO).

"Basilar artery occlusion is the 'orphan' of the large vessel occlusions," Raul Gomes Nogueira, MD, PhD, said here at a late-breaking abstract session at the 2020 International Stroke Conference (ISC).

"They account for about 5% of the large vessel occlusions — but have the most dismal prognosis." Severe disability and mortality rates associated with BAO, for example, reach an estimated 68% to 78%, he said.

The results, from the EVT for Acute Basilar Artery Occlusion Study (BASILAR), were also simultaneously published in JAMA Neurology.

Prior studies in this patient population are generally single-center, retrospective studies and "the numbers tend to be small," said Nogueira, who is affiliated with the Marcus Stroke and Neuroscience Center, Grady Memorial Hospital, Emory University School of Medicine in Atlanta, Georgia.

Nogueira and colleagues studied 829 consecutive adults who presented with an acute, symptomatic BAO. They examined a nationwide prospective registry study of people with radiologically confirmed BAO in 47 comprehensive stroke centers across 15 provinces in China.

The median age was 65 years and 74% were men. A total 182 participants received thrombolysis therapy within 6 hours of estimated BAO onset. The 647 people in the dual intervention group also received endovascular therapy within 24 hours.

Standard medical treatment included intravenous rt-PA or urokinase, antiplatelet drugs and systematic anticoagulation alone or in combination. Endovascular therapy included mechanical thrombectomy with stent retrievers and/or thromboaspiration, balloon angioplasty, stenting, intra-arterial thrombolysis, or a combination of these interventions.

Interestingly, participants were not randomly assigned, in part because of the favorable outcomes associated with endovascular therapy. "The high number of patients who received [the dual intervention] may suggest the existence of a lack of equipoise among participating centers," the researchers note.

Key Efficacy Endpoints

A significantly higher proportion of people in the dual treatment group achieved the primary outcome, functional improvement at 90 days, at 32%, compared with 9.3% in the thrombolysis-only group. This endpoint was defined as a modified Rankin Scale (mRS) score of 3 or less, which reflects an ability to walk independently. The difference was statistically significant (P < .001).

The absolute difference between groups was 22.7% (95% confidence interval [CI], 17.1% - 28.2%) with an adjusted odds ratio of 4.70 (95% CI, 2.53 - 8.75; P < .001) in favor of dual intervention.

The number needed to treat for one additional patient to be able to walk unassisted was 4.4.

Other outcomes, including differences in National Institutes of Health Stroke Scale scores from baseline to 5 to 7 days or discharge, as well as propensity score matching and subgroup analyses, likewise supported the superiority of using both interventions.

Safety Outcomes

Nogueira and colleagues also assessed safety. They found that symptomatic intracerebral hemorrhage (ICH) occurred in 45 patients, or 7.1% of the endovascular treatment group. In contrast, only one patient, or 0.5%, of the standard medical treatment alone cohort experienced an ICH. This difference was statistically significant (P < .001).

Mortality at 90 days was significantly lower in the endovascular therapy plus medical therapy group, 46.2%, compared with 71.4% in the standard medical treatment alone group (P < .001). 

The absolute difference in mortality was 25.2% (95% CI, 17.6% - 2.8%) favoring dual treatment, with an adjusted odds ratio of 2.93 (95% CI, 1.95 - 4.40; P < .001).

Rates of other serious adverse events during the 90-day follow-up period were similar in the two study groups, Nogueira said.

He acknowledged that the nonrandomized design was a limitation of the registry study, adding that "sometimes in life it's important to acknowledge the best of what can be done. It's very hard when you have access to thrombectomy to randomize people."

However, other researchers have attempted or are enrolling people with BAO into trials that randomly assign them to endovascular therapy and standard medical treatment or medical treatment alone.

The BEST trial in China, for example, randomly assigned 131 patients to these groups but was stopped early in September 2017. "The BEST trial was terminated prematurely because of loss of equipoise that led to a high crossover rate and drop in valid recruitment," the current researchers note.  

"The other two trials…are facing the challenge of whether they will achieve their inclusion target," they add, "because a growing number of stroke centers are unwilling to randomize patients to standard medical treatment alone after the many positive results of trials for endovascular treatment in patients with anterior-circulation stroke."

The BAOCHE trial from China, for example, is ongoing with approximately 110 patients enrolled so far.

Investigators for the Basilar Artery International Cooperation Study (BASICS) in the Netherlands just completed enrollment of their 300th and final patient in December 2019.

"We are hopeful BASICS trial will shed additional light," Nogueira said. The results are expected to be presented at the European Stroke Organization Conference in Vienna in May 2020.

More Guidance From MRI?

"With the advent of the stent retrievers and successful recanalization, we know there can be better outcomes for patients. And we know the morbidity and mortality of the basilar artery occlusions are so poor that we tend to want to be aggressive in these cases," session comoderator Shlee S. Song, MD, director of the Comprehensive Stroke Center and associate professor of neurology at Cedars-Sinai Medical Center in Los Angeles, California, told Medscape Medical News when asked to comment on the study. 

"I agree that we've lost equipoise in this cohort — that we really cannot do a randomized trial anymore. You know if you don't do anything, 90% of the time there will be a poor outcome," she added.

This is an important study for showing how BAO patients fare after endovascular treatment, Song said.

One unanswered question from the study is if any of the centers in China used magnetic resonance imaging to help determine the most appropriate candidates for endovascular treatment of these posterior circulation strokes, which is a common practice in the United States, she said.

The study was supported by the National Science Fund for Distinguished Young Scholars, Chongqing Major Disease Prevention and Control Technology Research Project, Army Medical University Clinical Medical Research Talent Training Program, and Major Clinical Innovation Technology Project of the Second Affiliated Hospital of the Army Military Medical University. Sing had no relevant disclosures. Nogueira's financial disclosures include working as a consultant for Stryker Neurovascular; as a principal investigator on the Imperative trial and the PROST trial; as a steering committee member for Biogen for the CHARM trial; as an advisory board member for Cerenovus/Neuravi, Phenox, Anaconda, Genentech, Biogen, Prolong Pharmaceuticals and Brainomix; and as an advisory board member with stock options for Viz.ai, Corindus Vascular Robotics, Vesalio, Ceretrieve, Astrocyte Pharmaceuticals, and Cerebrotech.

International Stroke Conference (ISC) 2020. Late-breaking abstract 17. Presented February 20, 2020.

JAMA Neurol. Published online February 20, 2020. Full text

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