Liquid Embolism of AVM Tied to High Cure Rate

Erik Greb

February 16, 2022

The Onyx Liquid Embolic System (Medtronic) effectively occludes cerebral arteriovenous malformations (cAVMs), new observational data suggest.

In a prospective, real-world study of more than 100 patients, use of the Onyx system was associated with a cure rate of 86% for cAVMs smaller than 3 cm.

"Endovascular treatment using Onyx is able to achieve, on its own, a very efficient cure rate with a low morbidity and mortality rate," investigator Laurent Spelle, MD, PhD, professor of neuroradiology at Paris-Saclay University and chair of NEURI, the Brain Vascular Center, Bicêtre Hospital, Paris, France, told Medscape Medical News.

Spelle presented the findings at the International Stroke Conference (ISC) 2022, which was held in New Orleans, Louisiana, and online.

Prospective, Multicenter Study

Currently, the main treatment options for cAVM are embolization, neurosurgery, and radiosurgery. The Onyx liquid system, one method of providing embolization, uses a biocompatible ethylene vinyl alcohol copolymer.

It has been used in Europe for 22 years as a curative treatment and as a treatment before radiosurgery or neurosurgery. In the United States, Onyx is indicated for presurgical and preradiotherapy treatment only.

For this analysis, the researchers conducted a prospective, multicenter study to evaluate the long-term safety and efficacy of Onyx for the embolization of cAVM as curative treatment or preoperative preparation.

They enrolled 165 patients in the nonrandomized, observational study, which was conducted at 15 hospitals in France. Eligible participants had an untreated cAVM.

Patients were assigned to one of three groups, according to the hospital's standard of care. One group underwent embolization with Onyx as curative treatment, one received Onyx as preparation for neurosurgery, and one underwent embolization with Onyx as preparation for radiosurgery.

The study's safety endpoints were device- and procedure-related serious adverse events at 1 month after each embolization. The efficacy endpoints were recovery at 12 months after the last embolization or neurosurgery, or at a minimum of 36 months after radiosurgery.

The researchers defined morbidity as a worsening of Modified Rankin Scale (mRS) score of 2 or more points for patients presenting with baseline mRS of 0 or 1, or a worsening of 1 or more points for patients with an mRS of 2 or greater at baseline. An independent clinical events committee and core laboratory adjudicated the results.

"A Fantastic Result"

In all, 140 patients were prospectively included, and 212 embolization procedures were performed. The population's mean age was 41.4 years, and 60% of participants were men. About 61% of patients presented with symptoms, the most common of which were progressive neurologic deficit (41.2%) and headache (36.5%).

Approximately 64% of the cAVMs were ruptured. Most (75.7%) were smaller than 3 cm, and the remainder were between 3 and 6 cm. Most patients (59.3%) did not have an aneurysm.

Eight (3.8%) adverse events were associated with the use of Onyx. The rate of procedure-related neurologic serious adverse events was 7.1% within 1 month post embolization. Three deaths occurred (2.1%), one of which was considered device- or procedure-related.

Eighty-seven patients underwent embolization alone. Fourteen of them did not complete the study (two died, five were lost to follow-up, and seven withdrew). Of the 73 who completed the study, 58 (79.5%) had complete occlusion and full recovery at last follow-up. An additional 6.8% had 99% occlusion.

In addition, 3.4% of the population had significant morbidity, and 18.4% presented at baseline with mRS of 3 to 5. Of the latter group, 81.3% had mRS of 0 to 2 at last visit.

Of 21 patients who underwent subsequent neurosurgery, 18 completed follow-up. Of this group, 94.4% had complete occlusion. Of 32 patients receiving subsequent radiosurgery, 54.8% had complete occlusion, which was "a little bit disappointing," said Spelle.

Overall, most patients (92.9%) had improved or stable mRS score. The overall mortality rate was 2.9%, and the rate of significant morbidity was 4.3%.

The rate of improved or stable mRS score was 94.3% for patients who underwent embolization alone, 85.7% for patients who also underwent neurosurgery, and 93.75% for patients who also underwent radiosurgery.

The mortality rate was 3.4% for patients who underwent embolization alone, 4.8% for patients who also underwent neurosurgery, and 0% for patients who also underwent radiosurgery.

The rate of significant morbidity was 2.3% for patients who underwent embolization alone, 9.5% for those who also underwent neurosurgery, and 6.25% for those who also underwent radiosurgery.

"We knew that this treatment was very effective, but this effectiveness was only known in a limited number of centers with a very high level of expertise," said Spelle. "We were very pleasantly surprised that a larger-scale, multicenter study conducted in 15 different hospitals in France could achieve such a fantastic result."

The study sites, however, were all departments in university hospitals with great experience in endovascular treatment of cAVM, he added.

Effective in Unruptured AVMs?

Commenting on the findings for Medscape Medical News, Mitchell Elkind, MD, professor of neurology and epidemiology, Columbia University, New York, said, "Arteriovenous malformations remain a relatively uncommon but serious cerebrovascular disorder." Elkind was not involved in the study. "Any additional tool in the armamentarium to treat these lesions is welcome," he added.

The study results are encouraging, said Elkind. They suggest that Onyx embolization can play an important role in the care of these patients. The treatment is associated with "low morbidity and excellent efficacy, particularly in combination with other surgical and radiographic approaches," Elkind added.

The lack of a direct comparison with alternative embolization materials is a limitation of the study, however. "It is hard to compare Onyx to other agents based on these results," said Elkind.

"It is also notable that one third of the patients in the study had unruptured AVMs, which at least in one randomized trial, ARUBA, were not clearly shown to benefit from an intervention at all," he continued.

It would have been valuable for the researchers to stratify the study results by ruptured vs unruptured AVMs, Elkind concluded.

The study was funded by Medtronic. Spelle reported receiving honoraria from the company. Elkind has disclosed no relevant financial relationships.

International Stroke Conference (ISC) 2022.

Follow Erik Greb on Twitter: @MedscapeErik.

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