title: Risk of hemorrhage and obliteration rates of LINAC-based radiosurgery for cerebral arteriovenous malformations treated after prior partial embolization.
abstract: OBJECTIVE
  We investigate patient outcome, risk of hemorrhage, and factors affecting obliteration after LINAC-based radiosurgery (RS) for cerebral arteriovenous malformations (AVM) treated after partial embolization.
  
  
  METHODS
  This analysis is based on 50 patients treated after prior embolization. According to the Spetzler-Martin criteria the AVM classification was as follows: 9 patients, Grade I (18%); 19, Grade II (38%); 18, Grade III (36%); and 4, Grade IV (8%). Median RS-based AVM score was 1.41. Median single dose was 18 Gy/ 80% isodose (range, 15-22 Gy) and median AVM volume was 4.0 cc (range, 0.2-22.6 cc). In all, 34 patients (68%) experienced hemorrhage before RS. Median follow-up was 3.1 year (range, 8.5 months to 15 years).
  
  
  RESULTS
  Actuarial complete obliteration rate was 67% after 3 years and 78% after 4 years. The complete obliteration rate was significantly higher in AVM <3 cm (92% vs. 60%, p < 0.01) and in AVM Spetzler-Martin Grade I/II (90% vs. 59%, p < 0,01). Intracranial hemorrhage after RS was seen in 6 patients (12%) after 8.5 months median. Annual bleeding risk was 7.9% after 1 year and 2.2% after 2 years. It was found that AVM diameter > or =3 cm (p < 0.006), AVM volume > or =4 cc (p < 0.01), AVM score > or =1.5 (p < 0.03), and single dose <18 Gy (p < 0.03) were associated with a significant higher bleeding risk.
  
  
  CONCLUSIONS
  The rate of obliteration after RS in AVM treated after prior partial embolization depends on size as well as Spetzler-Martin grade. The risk of intracranial hemorrhage is not increased after RS and depends on AVM score, size, and volume, as well as on applied single dose.
authors.affiliation: Department of RadioOncology, University of Heidelberg, 69120 Heidelberg, Germany. A.Zabel@dkfz-heidelberg.de
authors.forename: Angelika
authors.initials: A
authors.lastname: Zabel-du Bois
authors.forename: Stefanie
authors.initials: S
authors.lastname: Milker-Zabel
authors.forename: Peter
authors.initials: P
authors.lastname: Huber
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Schlegel
authors.forename: Jürgen
authors.initials: J
authors.lastname: Debus
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D002648:Child; D002675:Child, Preschool; D004621:Embolization, Therapeutic / Q000379:methods; D005500:Follow-Up Studies; D006801:Humans; D002538:Intracranial Arteriovenous Malformations / Q000145:classification / Q000601:surgery* / Q000628:therapy; D020300:Intracranial Hemorrhages / Q000209:etiology*; D008875:Middle Aged; D019106:Postoperative Hemorrhage / Q000209:etiology*; D016634:Radiosurgery / Q000009:adverse effects*; D018570:Risk Assessment