title: Embolization before radiosurgery reduces the obliteration rate of arteriovenous malformations.
abstract: OBJECTIVE
  To evaluate the arteriovenous malformation (AVM) obliteration rate and the clinical outcome after radiosurgery in patients with and without previous embolization.
  
  
  METHODS
  Of 244 patients who underwent linear accelerator radiosurgery for AVMs at the Sunnybrook Health Sciences Centre between 1989 and 2000, 61 patients had embolization before radiosurgery and complete follow-up for at least 3 years. For 47 of these 61 patients (Group A, embolization plus radiosurgery), we were able to find 47 matching patients without previous embolization (Group B, radiosurgery alone). This group of matching patients had the same AVM volume (after embolization in Group A), location, and marginal dose. The radiosurgery-based AVM score and the obliteration prediction index were calculated.
  
  
  RESULTS
  The median follow-up period was 44 months. Nidus obliteration was achieved in 22 patients in Group A (47%) and 33 patients in Group B (70%, P = 0.036). Permanent deficit related to hemorrhage or radiation occurred in three patients (6%) in Group A and three patients (6%) in Group B. During the first 3 years after radiosurgery, two patients (4%) in Group A experienced hemorrhage; in Group B, five patients (11%) experienced hemorrhage (P = 0.2). In Group B, two patients (4%) died and two patients (4%) had their AVM surgically removed. Both deaths were related to hemorrhage during the latency period. The excellent outcome (obliteration plus no deficit) in Group A was 47% compared with 64% in Group B (P = 0.146). There was no difference in the obliteration prediction index and the radiosurgery-based AVM score between Groups A and B. The predicted rates of obliteration and excellent outcome were 55 and 62.5%, respectively, according to the obliteration prediction index and the radiosurgery-based AVM score.
  
  
  CONCLUSIONS
  Embolization before radiosurgery significantly decreases the obliteration rate, even in AVMs with the same volume, location, and marginal dose. Although an excellent outcome rate was higher in the group without embolization, this was not statistically significant.
authors.affiliation: Division of Neurosurgery, University of Toronto, Sunnybrook Health Sciences Centre, Toronto Western Hospital, Toronto, Canada.
authors.forename: Yuri M
authors.initials: YM
authors.lastname: Andrade-Souza
authors.forename: Meera
authors.initials: M
authors.lastname: Ramani
authors.forename: Daryl
authors.initials: D
authors.lastname: Scora
authors.forename: May N
authors.initials: MN
authors.lastname: Tsao
authors.forename: Karel
authors.initials: K
authors.lastname: terBrugge
authors.forename: Michael L
authors.initials: ML
authors.lastname: Schwartz
mesh_terms: D000328:Adult; D003131:Combined Modality Therapy / Q000706:statistics & numerical data; D004621:Embolization, Therapeutic / Q000706:statistics & numerical data*; D005260:Female; D006801:Humans; D002538:Intracranial Arteriovenous Malformations / Q000401:mortality* / Q000473:pathology / Q000628:therapy*; D008297:Male; D009864:Ontario / Q000453:epidemiology; D011300:Preoperative Care / Q000379:methods / Q000706:statistics & numerical data*; D011379:Prognosis; D016634:Radiosurgery / Q000706:statistics & numerical data*; D015996:Survival Rate; D016896:Treatment Outcome