Testing the radiosurgery-based arteriovenous malformation score and the modified Spetzler-Martin grading system to predict radiosurgical outcome

Object. The aim of this study was to validate the radiosurgery-based arteriovenous malformation (AVM) score and the modified Spetzler-Martin grading system to predict radiosurgical outcome. Methods. One hundred thirty-six patients with brain AVMs were randomly selected. These patients had undergone a linear accelerator radiosurgical procedure at a single center between 1989 and 2000. Patients were divided into four groups according to an AVM score, which was calculated from the lesion volume, lesion location, and patient age (Group 1, AVM score < 1; Group 2, AVM score 1-1.49; Group 3, AVM score 1.5-2; and Group 4, AVM score > 2). Patients with a Spetzler-Martin Grade III AVM were divided into Grades IIIA (lesion > 3 cm) and IIIB (lesion < 3 cm). Sixty-two female (45.6%) and 74 male (54.4%) patients with a median age of 37.5 years (mean 37.5 years, range 5-77 years) were followed up for a median of 40 months. The median tumor margin dose was 15 Gy (mean 17.23 Gy, range 15-25 Gy). The proportions of excellent outcomes according to the AVM score were as follows: 91.7% for Group 1, 74.1% for Group 2, 60% for Group 3, and 33.3% for Group 4 (chi-square test, degrees of freedom (df) = 3, p < 0.001). Based on the modified Spetzler-Martin system, Grade I lesions had 88.9% excellent results; Grade 11, 69.6%; Grade 11113, 61.5%; and Grades IIIA and IV, 44.8% (chi-square test, df = 3, p = 0.047). Conclusions. The radiosurgery-based AVM score can be used accurately to predict excellent results following a single radiosurgical treatment for AVM. The modified Spetzler-Martin system can also predict radiosurgical results for AVMs, thus making it possible to use this system while deciding between surgery and radiosurgery.