Introduction: Due to the complexity of Spetzler-Martin (SM) grade IV-V arteriovenous malformations (AVM), the management of these lesions remains controversial. The aims of this multicenter, retrospective study are to evaluate outcomes after single-session stereotactic radiosurgery (SRS) for SM grade IV-V AVMs and determine predictive factors.
Methods: We pooled data from 233 patients (mean age 33 years) with SM grade IV (94.4%) or V AVMs (5.6%) treated with single-session SRS at eight participating centers in the International Gamma Knife Research Foundation. Pre-SRS embolization was performed in 71 AVMs (30.5%). The mean nidus volume, SRS margin dose, and follow-up duration were 9.7 cc, 17.3 Gy, and 84.5 months, respectively.
Results: At a mean follow-up interval of 84.5 months, favorable outcome was defined as AVM obliteration, no post-SRS hemorrhage, and no permanently symptomatic radiation-induced changes (RIC) and was achieved in 26.2% of patients. The actuarial obliteration rates at 3, 7, 10, and 12 years were 15%, 34%, 37% and 42%, respectively. The annual post-SRS hemorrhage rate was 3.0%. Symptomatic and permanent RIC occurred in 10.7% and 4% of the patients, respectively. Only larger AVM diameter (p=0.04) found to be an independent predictor of unfavorable outcome in the multivariate logistic regression analysis. The rate of favorable outcome was significantly lower for unruptured SM grade IV-V AVMs compared to ruptured ones (p=0.042). Prior embolization was a negative independent predictor of AVM obliteration (P=0.024) and radiologically evident RIC (P=0.05) in multivariate analyses.
Conclusions: In this multi-institutional study, single session SRS had limited efficacy in the management of SM grade IV-V AVMs. Favorable outcome was only achieved in a minority of unruptured SM grade IV-V AVMs, which supports less frequent utilization of SRS for the management of these lesions. A volume staged SRS approach for large AVMs represents an alternative approach for high grade AVM’s, but it requires further investigation.
Patient Care: This work shows that single session SRS should not likely be performed on unruptured, high grade AVM's.
Learning Objectives: The participants will learn about the SRS induced rate of obliteration, radiation induced changes, and favorable results associated with high grade AVM's.