title: Stereotactic proton beam therapy for intracranial arteriovenous malformations.
abstract: OBJECTIVE
  To investigate hypofractionated stereotactic proton therapy of predominantly large intracranial arteriovenous malformations (AVMs) by analyzing retrospectively the results from a cohort of patients.
  
  
  METHODS
  Since 1993, a total of 85 patients with vascular lesions have been treated. Of those, 64 patients fulfilled the criteria of having an arteriovenous malformation and sufficient follow-up. The AVMs were grouped by volume: <14 cc (26 patients) and > or =14 cc (38 patients). Treatment was delivered with a fixed horizontal 200 MeV proton beam under stereotactic conditions, using a stereophotogrammetric positioning system. The majority of patients were hypofractionated (2 or 3 fractions), and the proton doses are presented as single-fraction equivalent cobalt Gray equivalent doses (SFEcGyE). The overall mean minimum target volume dose was 17.37 SFEcGyE, ranging from 10.38-22.05 SFEcGyE.
  
  
  RESULTS
  Analysis by volume group showed obliteration in 67% for volumes <14 cc and 43% for volumes > or =14 cc. Grade IV acute complications were observed in 3% of patients. Transient delayed effects were seen in 15 patients (23%), becoming permanent in 3 patients. One patient also developed a cyst 8 years after therapy.
  
  
  CONCLUSIONS
  Stereotactic proton beam therapy applied in a hypofractionated schedule allows for the safe treatment of large AVMs, with acceptable results. It is an alternative to other treatment strategies for large AVMs. AVMs are likely not static entities, but probably undergo vascular remodeling. Factors influencing angiogenesis could play a new role in a form of adjuvant therapy to improve on the radiosurgical results.
authors.affiliation: Department of Radiation Oncology, Tygerberg Hospital, Tygerberg, South Africa. fv@sun.ac.za
authors.forename: Frederik J A I
authors.initials: FJ
authors.lastname: Vernimmen
authors.forename: Jacobus P
authors.initials: JP
authors.lastname: Slabbert
authors.forename: Jennifer A
authors.initials: JA
authors.lastname: Wilson
authors.forename: Shaheeda
authors.initials: S
authors.lastname: Fredericks
authors.forename: Roger
authors.initials: R
authors.lastname: Melvill
mesh_terms: D000293:Adolescent; D000328:Adult; D002648:Child; D019583:Dose Fractionation, Radiation; D005260:Female; D006801:Humans; D002538:Intracranial Arteriovenous Malformations / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D061766:Proton Therapy; D016634:Radiosurgery / Q000009:adverse effects / Q000379:methods*; D012189:Retrospective Studies; D011522:Protons
chemical_list: D011522:Protons