title: Alpha/beta ratio for arteriovenous malformations estimated from obliteration rates after fractionated and single-dose irradiation.
abstract: OBJECTIVE
  Results from single-dose radiosurgery have failed to yield reasonable alpha/beta ratios for obliteration rates of arteriovenous malformations (AVMs) in the framework of the linear-quadratic approach. We used outcome data from single-dose and fractionated radiotherapy for AVM to approach this problem.
  
  
  METHODS
  AVM obliteration rates observed in an updated historical series of fractionated radiotherapy and from six recent series of single-dose stereotactic radiosurgery were analyzed. Reciprocal total doses (1/D) and fraction sizes (d) of isoeffective fractionation schemes were entered into the rearranged form of the linear-quadratic equation: 1/D = (alpha/E) + (beta/E)d, and alpha/beta-ratios were calculated from the parameters of the regression line.
  
  
  RESULTS
  Fractionated radiotherapy with 20 Gy/4 Gy fractions, 50 Gy/2 Gy fractions and single-dose radiosurgery of approximately 13 Gy were isoeffective with crude obliteration rates of 13%. The analysis yielded an alpha/beta-ratio of 3.5 Gy. For small-sized AVMs (<3 cm), alpha/beta-ratios of 4.6-6.4 Gy were obtained.
  
  
  CONCLUSIONS
  These results support the view that radiosurgery for AVM can be understood as a typical late tissue effect with a high fractionation sensitivity. Fractionated radiotherapy is ineffective for AVMs and should be evaluated carefully in other benign targets.
authors.affiliation: Department of Radiation Oncology, University of Cologne, Cologne, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Kocher
authors.forename: Marc
authors.initials: M
authors.lastname: Wilms
authors.forename: Hans-Bruno
authors.initials: HB
authors.lastname: Makoski
authors.forename: Werner
authors.initials: W
authors.lastname: Hassler
authors.forename: Mohammad
authors.initials: M
authors.lastname: Maarouf
authors.forename: Harald
authors.initials: H
authors.lastname: Treuer
authors.forename: Jürgen
authors.initials: J
authors.lastname: Voges
authors.forename: Volker
authors.initials: V
authors.lastname: Sturm
authors.forename: Rolf-Peter
authors.initials: RP
authors.lastname: Müller
mesh_terms: D019583:Dose Fractionation, Radiation; D006801:Humans; D002538:Intracranial Arteriovenous Malformations / Q000601:surgery*; D016634:Radiosurgery; D011879:Radiotherapy Dosage