Effect of Prior Embolization on Cerebral Arteriovenous Malformation Radiosurgery Outcomes

BACKGROUND: Embolization before stereotactic radiosurgery (SRS) for cerebral arteriovenous malformations (AVM) has been shown to negatively affect obliteration rates, but its impact on the risks of radiosurgery-induced complications and latency period hemorrhage is poorly defined. OBJECTIVE: To determine, in a case-control study, the effect of prior embolization on AVM SRS outcomes. METHODS: We evaluated a database of AVM patients who underwent SRS. Propensity score analysis was used to match the case (embolized nidi) and control (nonembolized nidi) cohorts. AVM angioarchitectural complexity was defined as the sum of the number of major feeding arteries and draining veins to the nidus. Multivariate Cox proportional hazards regression analyses were performed on the overall study population to determine independent predictors of obliteration and radiation-induced changes. RESULTS: The matching process yielded 242 patients in each cohort. The actuarial obliteration rates were significantly lower in the embolized (31%, 49% at 5, 10 years, respectively) compared with the nonembolized (48%, 64% at 5, 10 years, respectively) cohort ( P = .003). In the multivariate analysis for obliteration, lower angioarchitectural complexity ( P < .001) and radiologically evident radiation-induced changes ( P = .016) were independent predictors, but embolization was not significant ( P = .744). In the multivariate analysis for radiologic radiation-induced changes, lack of prior embolization ( P = .009) and fewer draining veins ( P = .011) were independent predictors. CONCLUSION: The effect of prior embolization on AVM obliteration after SRS may be significantly confounded by nidus angioarchitectural complexity. Additionally, embolization could reduce the risk of radiation-induced changes. Thus, combined embolization and SRS may be warranted for appropriately selected nidi. ABBREVIATIONS: AVM, arteriovenous malformation RBAS, radiosurgery-based AVM score SRS, stereotactic radiosurgery VRAS, Virginia Radiosurgery AVM Scale