title: Dosimetric comparison of volumetric modulated arc therapy and linear accelerator-based radiosurgery for the treatment of one to four brain metastases.
abstract: BACKGROUND
  The purpose of this study is to compare and evaluate volumetric modulated arc therapy (VMAT) and linear accelerator-based radiosurgery (Linac RS) for the treatment of one to four brain metastases.
  
  
  METHODS
  Radiotherapy plans for 10 patients with 1 to 4 brain metastases that were planned and treated using conventional Linac RS were replanned using a mono-isocentric VMAT technique using two to four arcs. The same doses, target volumes and organs at risk (OAR) were used in both plans. The plans were evaluated for target volume coverage, dose conformity, homogeneity and dose to OAR.
  
  
  RESULTS
  For VMAT plans, 18/19 brain metastases met acceptable Radiation Therapy Oncology Group (RTOG) radiosurgery dose coverage, homogeneity and conformity criteria. There was no observed difference between the mean homogeneity indices for VMAT and Linac RS plans. VMAT plans had a lower mean RTOG conformity index compared with the Linac RS plans (1.10 ± 0.06 versus 2.06 ± 1.02). For the OAR, there was no difference in maximal doses to the brain stem, optic chiasm or optic nerves. The volume of normal brain receiving 12 Gy was lower in the VMAT plans (13.3 cm(3) versus 23.1 cm(3) ) compared with the Linac RS plans. The mean total number of monitor units (MUs) was 31.3% less in the VMAT plans (5231.2 MU versus 3593.5 MU).
  
  
  CONCLUSIONS
  Mono-isocentric VMAT plans using two to four arcs meet RTOG radiosurgery quality criteria in patients with one to four brain metastases, with an improvement in conformity and 12-Gy normal brain volume when compared with patients treated with Linac RS at our institution.
authors.affiliation: Nepean Cancer Care Centre, Nepean Hospital, Sydney, New South Wales, Australia; Crown Princess Mary Cancer Centre, Westmead Hospital, Westmead, New South Wales, Australia.
authors.forename: Alison L
authors.initials: AL
authors.lastname: Salkeld
authors.forename: Kylie
authors.initials: K
authors.lastname: Unicomb
authors.forename: Amy J
authors.initials: AJ
authors.lastname: Hayden
authors.forename: Kevin
authors.initials: K
authors.lastname: Van Tilburg
authors.forename: Shan
authors.initials: S
authors.lastname: Yau
authors.forename: Kenneth
authors.initials: K
authors.lastname: Tiver
mesh_terms: D001932:Brain Neoplasms / Q000556:secondary* / Q000628:therapy*; D006801:Humans; D016634:Radiosurgery / Q000379:methods*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods*; D012062:Relative Biological Effectiveness; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D016896:Treatment Outcome
keywords: brain; linear accelerator radiosurgery; metastasis; radiosurgery; volumetric modulated arc therapy