Radiosurgery for Arteriovenous Malformations: the University of Toronto Experience

Abstract

Background: From July 1989 to February 1996, 130 patients underwent sterotactic radiosurgery. We report the results of the first 50 patients eligible for a minimum of three years of follow-up. Methods: Twenty women and 30 men, (mean age: 37.5 years) were treated by dynamic rotation on a 6 MV linear accelerator. Prior treatment was embolization in seventeen, surgery in three and embolization and surgery in six. All had DSA and enhanced CT scanning, while some had MRI. Forty-seven treatments used a single isodose. Restricting eloquent normal tissue to 15 Gy, margin doses (at 50 -90% isodose) were 12 Gy (one patient); 15 Gy (sixteen patients); 20 Gy (31 patients); 25 Gy (two patients). Maximum diameters were: < 1.5 cm (12 patients); < 2.0 cm (nine patients); < 2.5 cm (twelve patients); < 3.0 cm (thirteen patients; 3.0 cm (four patients). Results: Forty-five patients were evaluable at three years, with thirty-nine having angiography. Twenty-five had angiographically confirmed obliterations; two had parenchymal AVMs obliterated but with residual dural components; four had MRI evidence of obliteration (refused angiography). One patient acutely had a seizure; one patient (with hemorrhages, resection, and embolizations preceding two applications of radiosurgery, separated by 3.5 years) had worsening of memory. Conclusions: Our uncorrected (five patients unevaluable at three years) and corrected angiographically confirmed obliteration rates are 54% and 60% respectively. Our follow-up (98% accounting of cohort; 78% angiographic rate) and explicit derivation of denominators help delineate the efficacy of radiosurgery at these doses. RESUME: La radiochirurgie dans le traitement des malformations arterio-veineuses: I'experience de I'Universite de Toronto. Introduction: De juillet 1989 a fevrier 1996, 130 patients ont subi une radiochirurgie stereotaxique. Nous rapportons les resultats des premiers 50 patients chez qui nous avons effectue un suivi minimum de trois ans. Methodes: Vingt femmes et 30 hommes, (age moyen: 37.5 ans) ont ete traites par rotation dynamique sur un accelerateur lineaire de 6 MV. Une embolisation avait ete effectuee anterieurement chez dix-huit, une chirurgie chez trois et une embolisation ainsi qu'une chirurgie chez six. Tous avaient eu une DSA et un CT scan avec rehaussement, alors que quelques uns avaient eu une RMN. Une isodose unique a ete utilisee pour quarante-sept traitements. En limitant la dose au tissu normal a 15 Gy, les doses aux limites de la lesion (a 50 -90% de l'isodose) etaient de 12 Gy (un patient); 15 Gy (16 patients); 20 Gy (31 patients); 25 Gy (2 patients). Les diametes maximums etaient < 1.5 cm (12 patients); < 2.0 cm (8 patients); < 2.5 cm (13 patients); < 3.0 cm (13 patients); 3.0 cm (4 patients). Resultats: Quarante-cinq patients ont ete evalues apres 3 ans de suivi, dont 39 ont eu une angiographie. Vingt-cinq avaient une obliteration confirmee par l'angiographie; 2 avaient une MAV parenchymateuse obliteree mais avec une composante durale residuelle; 4 avaient des sig...

Factors Predictive of Obliteration After Arteriovenous Malformation Radiosurgery

“…The results from this series of 48 patients treated for AVMs with linear accelerator-based SRS are consistent with other series reported in the literature which suggest complete nidus obliteration in 60-90% of patients 15,[22][23][24][25][26] . The AVMs were initially treated with Gamma Knife radiosurgery 13 27 reported on their four year experience in 65 patients with AVMs using SRS for smaller lesions (<3cm diameter) and Spetzler-Martin grades 1 and 2.…”

“…The actuarial complete obliteration rate was 67% after four years. Young et al 26 reported an angiographically confirmed obliteration rate of 60% in a series of 50 patients.…”

“…Subsequently, a number of institutions have reported obliteration rates following linear accelerator-based radiosurgery [15][16][17][18][19]26 . Zabel et al 18 treated 110 patients with linear accelerator-based radiosurgery.…”

Computational Analyses of Arteriovenous Malformations in Neuroimaging

“…A standard dose of 25 Gray (Gy) for volumes <4 cm 3 and 20 Gy for AVM volumes >4 cm 3 was administered, limiting the dose to 15 Gy for lesions near eloquent areas. The outcome of radiosurgery was considered 3 years after the treatment, and it was dichotomized as complete obliteration (total disappearance of the nidus on the MRA and/or no abnormal flow voids on MRI), or incomplete obliteration. The FD was computed on the MRI ROI, which was selected for the radiosurgical treatment (see Methods in Di Ieva et al) .…”

“…The anatomy of the AVM can be characterized by means of magnetic resonance imaging (MRI) and magnetic resonance angiography (MRA), computed tomography angiography (CTA), and cerebral angiography . Several angioarchitectural parameters have been proposed such as size and volume of the nidus, venous drainage, arterial enlargement, presence of sprouting and nonsprouting angiogenesis, presence of pseudophlebetic pattern and flow pattern, venous ectasia, number of draining veins, and number of venous rerouting . Nonetheless, several of these parameters have not been standardized yet in an objective manner, and they are still estimated by the neuroradiologists, which leads to the possibility of intra‐ and interobserver variability in their description.…”