title: Proton radiation therapy for retinoblastoma: comparison of various intraocular tumor locations and beam arrangements.
abstract: OBJECTIVE
  To study the optimization of proton beam arrangements for various intraocular tumor locations; and to correlate isodose distributions with various target and nontarget structures.
  
  
  METHODS
  We considered posterior-central, nasal, and temporal tumor locations, with straight, intrarotated, or extrarotated eye positions. Doses of 46 cobalt grey equivalent (CGE) to gross tumor volume (GTV) and 40 CGE to clinical target volume (CTV) (2 CGE per fraction) were assumed. Using three-dimensional planning, we compared isodose distributions for lateral, anterolateral oblique, and anteromedial oblique beams and dose-volume histograms of CTVs, GTVs, lens, lacrimal gland, bony orbit, and soft tissues.
  
  
  RESULTS
  All beam arrangements fully covered GTVs and CTVs with optimal lens sparing. Only 15% of orbital bone received doses > or =20 CGE with a lateral beam, with 20-26 CGE delivered to two of three growth centers. The anterolateral oblique approach with an intrarotated eye resulted in additional reduction of bony volume and exposure of only one growth center. No appreciable dose was delivered to the contralateral eye, brain tissue, or pituitary gland.
  
  
  CONCLUSIONS
  Proton therapy achieved homogeneous target coverage with true lens sparing. Doses to orbit structures, including bony growth centers, were minimized with different beam arrangements and eye positions. Proton therapy could reduce the risks of second malignancy and cosmetic and functional sequelae.
authors.affiliation: Department of Radiotherapy, University of Piemonte Orientale, Novara, Italy.
authors.forename: Marco
authors.initials: M
authors.lastname: Krengli
authors.forename: Eugen B
authors.initials: EB
authors.lastname: Hug
authors.forename: Judy A
authors.initials: JA
authors.lastname: Adams
authors.forename: Alfred R
authors.initials: AR
authors.lastname: Smith
authors.forename: Nancy J
authors.initials: NJ
authors.lastname: Tarbell
authors.forename: John E
authors.initials: JE
authors.lastname: Munzenrider
mesh_terms: D006801:Humans; D061766:Proton Therapy; D011859:Radiography; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D012175:Retinoblastoma / Q000000981:diagnostic imaging / Q000532:radiotherapy*; D011522:Protons
chemical_list: D011522:Protons