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001. Early Obliteration of Pediatric Brain Arteriovenous Malformations after Stereotactic Radiosurgery: An International Multicenter Study

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Authors: Rebecca Burke, MD

Introduction:
Rupture of brain arteriovenous malformations (AVMs) cause the majority of spontaneous intracerebral hemorrhages in the post-infancy pediatric population. AVM obliteration after SRS virtually eliminates the risk of hemorrhage. However, patients remain at risk for AVM hemorrhage during the latency period between treatment and obliteration. Early obliteration has not been evaluated in a cohort of exclusively pediatric AVMs. The aims of this study of pediatric patients with SRS-treated AVMs are to (1) determine predictors of early obliteration, and (2) compare the outcomes in patients that achieved early versus late obliteration.Methods: We performed a retrospective review of the International Radiosurgery Research Foundation AVM database. Obliterated pediatric AVMs were sorted into early (obliteration ?24 months after SRS) versus late (obliteration >24 months after SRS) responders. Predictors of early obliteration were identified, and the outcomes of each group were compared.
Results:
The overall study cohort comprised 345 pediatric patients with obliterated AVMs. The early and late obliteration cohorts comprised 95 (28%) and 250 (72%) patients, respectively. Independent predictors of early obliteration were female gender, single SRS treatment, higher margin dose, higher isodose line, deep AVM location, and smaller AVM volume. The crude rate of post-SRS hemorrhage was 50% lower in the early (3.2%) versus late (6.4%) obliteration cohorts but this difference was not statistically significant (p=0.248). The other outcomes of the early versus late obliteration cohorts were similar, with respect to symptomatic radiation-induced changes (RIC), cyst formation, and tumor formation.
Conclusion:
Approximately one-quarter of pediatric AVMs that obliterate after SRS will achieve this radiological endpoint within 24 months of initial SRS. We identified multiple factors associated with early obliteration, which may aid in prognostication and management. The overall risk of delayed hemorrhage, RIC, cyst formation, and tumor formation, were not statistically different in patients with early versus late obliteration.