title: Outcomes of Volume-Staged Radiosurgery for Cerebral Arteriovenous Malformations Larger Than 20 cm(3) with More Than 3 Years of Follow-Up.
abstract: OBJECTIVE
  Treatment of extremely large cerebral arteriovenous malformations (AVMs) is challenging. Although volume-staged stereotactic radiosurgery (SRS) is a possible multimodal treatment option for such lesions, reports of these procedures are scarce. We evaluated the efficacy and safety of volume-staged SRS in patients with AVMs >20 cm(3) with >3 years of follow-up.
  
  
  METHODS
  Between 2005 and 2012, 18 patients with AVMs >20 cm(3) were treated by volume-staged SRS. The median target volume was 38 cm(3) (interquartile range, 31-53 cm(3)). Treatment was conducted in 2-3 stages with a median interval of 6 months.
  
  
  RESULTS
  The median follow-up period from the last SRS treatment was 53 months (interquartile range, 41-75 months). Complete nidus obliteration was achieved in 6 patients (33%), and the obliteration rate at 5 years after initial SRS was 35% by the Kaplan-Meier method. The annual hemorrhage rate after last SRS treatment was 3.9% (95% confidence interval, 0.8%-11.5%). Radiation-induced adverse effects occurred in 2 patients.
  
  
  CONCLUSIONS
  In our series, volume-staged SRS for AVMs >20 cm(3) achieved a nidus obliteration rate of 35% at 5 years. There was still a high risk for hemorrhage (∼ 4% per year) after treatment, which seemed to be higher than the rate commonly observed in the posttreatment course of single-session SRS for average-size AVMs. Further cases will help determine whether volume-staged SRS could be routinely considered, based on its efficacy and risks, including comparison with the natural history of large AVMs.
authors.affiliation: Department of Neurosurgery, The University of Tokyo Hospital, Tokyo, Japan. Electronic address: hanakita-s@umin.ac.jp.
authors.forename: Shunya
authors.initials: S
authors.lastname: Hanakita
authors.affiliation: Department of Neurosurgery, The University of Tokyo Hospital, Tokyo, Japan.
authors.forename: Masahiro
authors.initials: M
authors.lastname: Shin
authors.affiliation: Department of Neurosurgery, The University of Tokyo Hospital, Tokyo, Japan.
authors.forename: Tomoyuki
authors.initials: T
authors.lastname: Koga
authors.affiliation: Department of Radiology, The University of Tokyo Hospital, Tokyo, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Igaki
authors.affiliation: Department of Neurosurgery, The University of Tokyo Hospital, Tokyo, Japan.
authors.forename: Nobuhito
authors.initials: N
authors.lastname: Saito
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D002533:Cerebral Angiography; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D002538:Intracranial Arteriovenous Malformations / Q000150:complications / Q000473:pathology* / Q000601:surgery*; D020300:Intracranial Hemorrhages / Q000453:epidemiology / Q000209:etiology; D053208:Kaplan-Meier Estimate; D008297:Male; D008875:Middle Aged; D019635:Neurosurgical Procedures / Q000009:adverse effects / Q000379:methods*; D011183:Postoperative Complications / Q000453:epidemiology; D016634:Radiosurgery / Q000009:adverse effects / Q000379:methods*; D016019:Survival Analysis; D016896:Treatment Outcome; D055815:Young Adult
keywords: Gamma Knife radiosurgery; Large arteriovenous malformation; Staged stereotactic radiosurgery