title: Volumetric Modulated Arc Therapy (VMAT) make a difference in retro-orbital irradiation treatment of patients with bilateral Graves' ophthalmopathy. Comparative analysis of dosimetric parameters from different radiation techniques.
abstract: BACKGROUND
  Graves' ophthalmopathy is the commonest extrathyroidal manifestation of Graves' disease. Treatment options include steroid therapy, corrective/decompressive surgery, radiation therapy or combination of these approaches.
  
  
  OBJECTIVE
  Our purpose was to investigate if retro-orbital irradiation with Volumetric Modulated Arc Therapy (VMAT) yielded better target coverage and dose sparing to adjacent normal structures compared to 3-Dimensional Conformal Radiotherapy (3DCRT) and Lateral Opposing Conformed Fields (LOCF).
  
  
  METHODS
  Fourteen consecutive patients diagnosed with bilateral Graves' ophthalmopathy were prospectively recruited into this study from August 2012 until August 2014. An individual VMAT, 3DCRT and LOF plan was created for each patient. Conformity Index (CI), Homogeneity Index (HI) and other dosimetric parameters of the targets and organs-at-risk (OAR) were analyzed in all 28 orbits compared between the different techniques.
  
  
  RESULTS
  CI generated by VMAT was superior to that produced by 3DCRT(p < .001) and LOF (p < .001). As expected, 3DCRT was also superior to LOF (p = .007). Regarding the OARs sparing dose (lens, globes, retina and lacrimal glands), VMAT showed a significant benefit when compared with 3DCRT and LOCF, with no differences between the two latter techniques.
  
  
  CONCLUSIONS
  VMAT should be preferred over 3DCRT and LOF for bilateral Graves' ophthalmopathy treatment.
authors.affiliation: Radiation Oncology Department, Hospital Dr. Negrin, Las Palmas de Gran Canaria, Spain.
authors.forename: Iñigo
authors.initials: I
authors.lastname: San-Miguel
authors.affiliation: Radiation Oncology Department, Hospital Dr. Negrin, Las Palmas de Gran Canaria, Spain.
authors.forename: Ruth
authors.initials: R
authors.lastname: Carmona
authors.affiliation: Medical Physics Department, Hospital Dr. Negrin, Las Palmas de Gran Canaria, Spain.
authors.forename: Luis
authors.initials: L
authors.lastname: Luque
authors.affiliation: Radiation Oncology Department, Hospital Dr. Negrin, Las Palmas de Gran Canaria, Spain.
authors.forename: Raquel
authors.initials: R
authors.lastname: Cabrera
authors.affiliation: Radiation Oncology Department, Hospital Dr. Negrin, Las Palmas de Gran Canaria, Spain.
authors.forename: Marta
authors.initials: M
authors.lastname: Lloret
authors.affiliation: Ofthalmology Department, Hospital Dr. Negrin, Las Palmas de Gran Canaria, Spain.
authors.forename: Francisco
authors.initials: F
authors.lastname: Rutllan
authors.affiliation: Radiation Oncology Department, Hospital Dr. Negrin, Las Palmas de Gran Canaria, Spain.
authors.forename: Pedro Carlos
authors.initials: PC
authors.lastname: Lara
keywords: Dosimetric parameters; Graves’ opthalmopathy; Radiotherapy; VMAT