title: Repeated radiosurgery for incompletely obliterated arteriovenous malformations.
abstract: OBJECTIVE
  The goal of this study was to define treatment results of repeated arteriovenous malformation (AVM) radiosurgery, namely AVM obliteration and complications.
  
  
  METHODS
  The authors analyzed their experience with repeated AVM radiosurgery performed in 41 patients for whom follow-up review lasted at least 2 years. The median duration of follow up was 34 months (range 7-65 months) after repeated radiosurgery in this group. The residual nidus was located within the area of focus (in field) of the initial radiosurgery in 28 patients (68%). Initial doses to the margin varied from 12.5 to 20 Gy (median 18 Gy). During repeated treatment the dose to the margin varied from 12.5 to 20 Gy (median 17 Gy) and the retreated volumes ranged from 0.4 to 7 cm3 (median 2.1 cm3). Follow-up angiography performed at least 2 years postradiosurgery revealed complete AVM obliteration in 21 (70%) of 30 patients. The estimated overall 2-year obliteration rate, based on findings on magnetic resonance imaging (eight of 11 obliterated) and angiography (29 of 41 obliterated) was 71%. Obliteration rates correlated with margin doses (p = 0.0045) with a trend toward higher rates in cases with in-field nidus persistence (p = 0.0637). The dose-response curve for AVM nidus obliteration was not significantly different from that of the initial radiosurgery. In two patients (5%) intracranial AVM hemorrhage developed within 125.9 risk years after repeated radiosurgery (1.6% per patient year). Persistent symptomatic adverse radiation effects developed in two (5%) of 41 patients following repeated radiosurgery. Postradiosurgical imaging changes were identified in 11 (27%) of 41 patients, which correlated with a 12-Gy volume from repeated surgery (p = 0.019).
  
  
  CONCLUSIONS
  When necessary, repeated AVM radiosurgery achieves obliteration with an acceptable risk. Despite the effects of previous irradiation, repeated radiosurgery required similar or slightly higher radiation doses to achieve the same in-field obliteration rates as those needed to obliterate an AVM that had not been treated by radiation previously.
authors.affiliation: Department of Neurological Surgery, University of Pittsburgh School of Medicine, and the Center for Image-Guided Neurosurgery, University of Pittsburgh Medical Center, Pennsylvania, USA.
authors.forename: S
authors.initials: S
authors.lastname: Maesawa
authors.forename: J C
authors.initials: JC
authors.lastname: Flickinger
authors.forename: D
authors.initials: D
authors.lastname: Kondziolka
authors.forename: L D
authors.initials: LD
authors.lastname: Lunsford
mesh_terms: D000293:Adolescent; D000328:Adult; D002533:Cerebral Angiography; D002648:Child; D002675:Child, Preschool; D004307:Dose-Response Relationship, Radiation; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D002538:Intracranial Arteriovenous Malformations / Q000175:diagnosis / Q000000981:diagnostic imaging / Q000601:surgery*; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D016634:Radiosurgery; D012086:Reoperation; D013238:Stereotaxic Techniques; D016896:Treatment Outcome