1109. Hemorrhage Risk of Brain Arteriovenous Malformations before and after Stereotactic Radiosurgery: A Multicenter Study

Authors: Dale Ding, MD; Ching-Jen Chen, MD; Robert Starke, MD, MSc; Hideyuki Kano, MD; John Lee, MD; David Mathieu, MD; Caleb Feliciano, MD; Inga Grills, MD; Douglas Kondziolka, MD; Gene Barnett, MD; L. Dade Lunsford, MD; Jason Sheehan, MD, PhD (LOUISVILLE, KY)

Introduction: The hemorrhage risks of brain arteriovenous malformations (AVM) before and after treatment with stereotactic radiosurgery (SRS) have not been fully characterized. The aims of this multicenter, retrospective cohort study are to assess and compare the rates of pre- and post-SRS AVM hemorrhage and to determine predictors. Methods: We pooled AVM SRS data from eight institutions participating in the International Radiosurgery Research Foundation (IRRF). Predictors of post-SRS hemorrhage were determined using a multivariate logistic regression model. Pre- and post- SRS hemorrhage rates were compared using Fisher’s exact test. Ruptured and unruptured AVMs were matched in a 1:1 ratio using propensity scores, and their outcomes were compared. Results: The study cohort comprised 2,320 AVM patients who underwent SRS. Deep AVM location (OR=1.86, 95% CI: 1.19-2.92; p=0.007), the presence of an AVM-associated aneurysm (OR=2.44, 95% CI: 1.63-3.66; p<0.001), and lower SRS margin dose (OR=0.93, 95% CI: 0.88-0.98; p=0.005) were independent predictors of post-SRS hemorrhage. The post-SRS hemorrhage rate was lower for obliterated versus patent AVMs (6.0 vs. 22.3 hemorrhages/1,000 person-years; p<0.001). The AVM hemorrhage rate decreased from 15.4 hemorrhages/1,000 person-years before SRS to 11.9 after SRS (p=0.001). The outcomes of the matched ruptured versus unruptured AVM cohorts were similar. Conclusion: SRS appears to reduce the risk of AVM hemorrhage, although this effect is predominantly driven by obliteration. Deep-seated AVMs are more likely to rupture during the latency period after SRS. AVM-associated aneurysms should be considered for selective occlusion prior to SRS of the nidus to ameliorate the post-SRS hemorrhage rate of these lesions.