Validation of a Radiosurgery-Based Grading System for Arteriovenous Malformations

摘要

Purpose: The Spetzler-Martin grade (SMG) accurately predicts outcome after surgical resection of arteriovenous malformations (AVM); however, its application to radio-surgery is limited because of insensitivity to AVM volume and location. Recently, a radiosurgical grading system was developed by the University of Pittsburgh/Mayo Clinic to predict outcomes for Gamma Knife?radiosurgery. This retrospective study seeks to independently validate the radiosurgery grade (RSG) and determine its application to linear accelerator-based radiosurgery. Methods and Materials: Twenty patients were treated with Radionics XKnife~(TM) LINAC-based radiosurgery for AVMs between 1990 and 2002 (median follow-up, 35 months). Outcomes based on obliteration rates and post-treatment neurological deficits were analyzed according to RSG and SMG. The following equation describes the RSG: AVM score = (0.1) (AVM volume in cm~3) + (0.02) (age in years) + (0.3) (location) with frontal/temporal = 0; parietal/occipital/intraventricular/corpus callo-sum/cerebellar = 1; and basal ganglia/thalamus/brainstem = 2. Results: Overall, 65% had excellent outcomes, 0% good, 5% fair, 25% unchanged, and 5% poor. Excellent outcomes were achieved in 100, 50 and 20% of patients with RSG 0.6-1.3, 1.4-1.7, and 1.9-2.4, respectively. Spearman's correlation coefficient for RSG versus excellent/non-excellent outcomes was 0.70 (p = 0.0014). For SMG 1-4, the percentage of patients with excellent outcomes were 100, 56, 80, and 0%, respectively. The SMG Spearman's correlation coefficient was 0.34 (p = 0.15). Two patients (10%), with RSGs of 1.9 and 1.6, developed radionecrosis. No post-radiosurgery hemorrhage or AVM-related deaths occurred. Conclusions: The RSG accurately predicted excellent patient outcomes, thus validating this grading system and suggesting its applicability to linear accelerator-based radiosurgery for AVMs. Future research for AVMs treated with radiosurgery should now report outcomes using this RSG.