title: Pretreatment predictors of adverse radiation effects after radiosurgery for arteriovenous malformation.
abstract: OBJECTIVE
  To identify vascular and dosimetric predictors of symptomatic T2 signal change and adverse radiation effects after radiosurgery for arteriovenous malformation, in order to define and validate preexisting risk models.
  
  
  METHODS
  A total of 125 patients with arteriovenous malformations (AVM) were treated at our institution between 2005 and 2009. Eighty-five patients have at least 12 months of clinical and radiological follow-up. Any new-onset headaches, new or worsening seizures, or neurological deficit were considered adverse events. Follow-up magnetic resonance images were assessed for new onset T2 signal change and the volume calculated. Pretreatment characteristics and dosimetric variables were analyzed to identify predictors of adverse radiation effects.
  
  
  RESULTS
  There were 19 children and 66 adults in the study cohort, with a mean age of 34 (range 6-74). Twenty-three (27%) patients suffered adverse radiation effects (ARE), 9 patients with permanent neurological deficit (10.6%). Of these, 5 developed fixed visual field deficits. Target volume and 12 Gy volume were the most significant predictors of adverse radiation effects on univariate analysis (p < 0.001). Location and cortical eloquence were not significantly associated with the development of adverse events (p = 0.12). No additional vascular parameters were identified as predictive of ARE. There was a significant target volume threshold of 4 cm(3), above which the rate of ARE increased dramatically. Multivariate analysis target volume and the absence of prior hemorrhage are the only significant predictors of ARE. The volume of T2 signal change correlates to ARE, but only target volume is predictive of a higher volume of T2 signal change.
  
  
  CONCLUSIONS
  Target volume and the absence of prior hemorrhage is the most accurate predictor of adverse radiation effects and complications after radiosurgery for AVMs. A high percentage of permanent visual field defects in this series suggest the optic radiation is a critical radiosensitive structure.
authors.affiliation: Gamma Knife Unit, Division of Neurosurgery, University Health Network, Toronto, Canada.
authors.forename: Caroline
authors.initials: C
authors.lastname: Hayhurst
authors.forename: Eric
authors.initials: E
authors.lastname: Monsalves
authors.forename: Monique
authors.initials: M
authors.lastname: van Prooijen
authors.forename: Michael
authors.initials: M
authors.lastname: Cusimano
authors.forename: May
authors.initials: M
authors.lastname: Tsao
authors.forename: Cynthia
authors.initials: C
authors.lastname: Menard
authors.forename: Abhaya V
authors.initials: AV
authors.lastname: Kulkarni
authors.forename: Michael
authors.initials: M
authors.lastname: Schwartz
authors.forename: Gelareh
authors.initials: G
authors.lastname: Zadeh
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000704:Analysis of Variance; D002648:Child; D005260:Female; D006261:Headache / Q000209:etiology; D006801:Humans; D002538:Intracranial Arteriovenous Malformations / Q000175:diagnosis / Q000601:surgery*; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D008875:Middle Aged; D010291:Paresis / Q000209:etiology; D011832:Radiation Injuries / Q000175:diagnosis*; D016634:Radiosurgery / Q000009:adverse effects* / Q000379:methods; D011879:Radiotherapy Dosage; D012189:Retrospective Studies; D018570:Risk Assessment / Q000379:methods; D012640:Seizures / Q000209:etiology; D014786:Vision Disorders / Q000209:etiology; D055815:Young Adult