Nancy A. Melville

May 15, 2015

Washington, DC — A new scale providing clinicians and patients with a risk stratification for the chances of recanalization after endovascular treatment of aneurysm showed a good predictive value when validated at five treatment centers.

"Institutions can use this stratification scale to determine their own recurrence rate," said first author Christopher S. Ogilvy, MD, a professor of neurosurgery at Harvard Medical School in Boston, Massachusetts.

"In getting this predictive value for the rate of recurrence, we find it incredibly helpful in counseling aneurysm patients and their families, particularly in balancing the risks and efficacy of surgery against endovascular therapy."

The results were presented here at the American Association of Neurological Surgeons (AANS) 83rd Annual Meeting.

Rates of recanalization following endovascular treatment for aneurysms generally range from 17% to 30%, according previous studies.

Dr Ogilvy and his colleagues developed the Aneurysm Recanalization Stratification Scale to provide a tool for gauging a comprehensive risk assessment.

As described in the initial study, published this year in Neurosurgery, the system was developed according to a retrospective review of the medical records of 268 patients who underwent endovascular treatment for intracranial aneurysms at Beth Israel Deaconess Medical Center, Boston, Massachusetts, between 2007 and 2013.

Using multivariable logistic regression, a composite risk score was developed showing factors including size (>10 mm), aneurysm rupture, stent assistance, and post-treatment degree of aneurysm occlusion as independent factors associated with retreatment with a follow-up of 3 months or more.

Intraluminal thrombosis and flow diversion meanwhile were associated with a trend for retreatment risk.

On the basis of the findings, two points each were assigned to predictors including size greater than 10 mm, rupture, and the presence of thrombus.

In addition, treatment-related predictors factoring into the scale included stent assistance, –1 point; flow diversion, –2 points; class 2 Raymond Roy occlusion, 1 point; and class 3 Raymond Roy occlusion, 2 points.

For the new study, the authors externally validated the scale using independent cohorts from five centers, for a total of 1543 patients.

In addition to Beth Israel Deaconess, the centers included the University of Alabama at Birmingham; the University of Buffalo in New York; the University of Calgary in Alberta, Canada; and the University of Florida in Gainesville.

The analysis showed moderate variability in retreatment rates among the centers, which were 29.5%, 9.9%, 9.6%, 26.3%, 19.7%, and 18.3% for the combined cohort.

The Aneurysm Recanalization Stratification Scale meanwhile showed good predictive value for retreatment, with C-statistics of 0.799, 0.943, 0.780, 0.695, 0.755, and 0.719 for each center and the combined cohort, respectively.

On the basis of the findings, the probability of retreatment according to the risk score ranged from a low of 4.9% with a score of –2 to a 100% risk with a score of 7.

"Our current data demonstrates a validation of the Aneurysm Recanalization Stratification Scale in a large number of patients from five institutions," Dr Ogilvy said.

Despite the promising results, however, the study had shortcomings that prompted some caution.

"I thought it was an interesting attempt at stratifying the risk of recanalization," neurosurgeon Robert E. Harbaugh, MD, president of the AANS, told Medscape Medical News.

"However, the study suffered from nonblinded assessment, which will always introduce bias, and I doubt that this scale will be widely used or make a significant difference in regard to how patients are managed," said Dr Harbaugh, who is director of the Institute of the Neurosciences and chair of the Department of Neurosurgery at Penn State University, Milton S. Hershey Medical Center in Pennsylvania.

Discussant John Laidlaw, MD, from the Royal Melbourne Hospital in Australia, also saw some flaws in the study.

"The study describes retreatment, but retreatment is not the same as recanalization, and I think recanalization and possible aneurysm-rupture risk [are] what clinicians and the patients need to know," he said in discussing the talk.

"Of note, nearly 20% of patients had a relatively short follow-up and therefore this report probably underestimates the likely retreatment rate."

In light of those and other concerns, Dr Laidlaw concluded, "I question whether this model is going to really help us predict which aneurysms are prone to late rebleed."

Dr Ogilvy, Dr Harbaugh, and Dr Laidlaw have disclosed no relevant financial relationships.

American Association of Neurological Surgeons (AANS) 83rd Annual Meeting. Abstract 728. Presented May 5, 2015.

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