title: Bladder cancer radiotherapy margins: a comparison of daily alignment using skin, bone or soft tissue.
abstract: OBJECTIVE
  To determine the clinical target volume (CTV) to planning target volume (PTV) margins required for bladder coverage when using skin or bony or soft tissue matching on a daily basis.
  
  
  METHODS
  Twenty-seven patients with T2-T4 transitional cell carcinoma of the bladder were treated with daily online adaptive image-guided radiotherapy using cone beam computed tomography. All daily CTVs were contoured by a single observer. A retrospective comparison of coverage of the bladder CTV using skin, bone and soft tissue matching was conducted.
  
  
  RESULTS
  With the skin set-up, bladder CTV coverage with a margin of 0.5, 1.0, 1.5, 2.0 and 2.5 cm was 0, 19, 56, 93 and 96%, respectively. For the daily set-up based on bone, the respective coverage was 0, 41, 63, 89 and 96%. For soft tissue set-up based on the geometric centre of the bladder, coverage was 52, 89, 96, 100 and 100%, respectively.
  
  
  CONCLUSIONS
  Based on coverage of the CTV, the required CTV to PTV margins are smaller for the daily online soft tissue set-up compared with skin or bone.
authors.affiliation: Division of Radiation Oncology, Peter MacCallum Cancer Institute, Melbourne, Victoria, Australia. farshad.foroudi@petermac.org
authors.forename: F
authors.initials: F
authors.lastname: Foroudi
authors.forename: D
authors.initials: D
authors.lastname: Pham
authors.forename: M
authors.initials: M
authors.lastname: Bressel
authors.forename: J
authors.initials: J
authors.lastname: Wong
authors.forename: A
authors.initials: A
authors.lastname: Rolfo
authors.forename: P
authors.initials: P
authors.lastname: Roxby
authors.forename: T
authors.initials: T
authors.lastname: Kron
mesh_terms: D001842:Bone and Bones / Q000033:anatomy & histology; D054893:Cone-Beam Computed Tomography; D019583:Dose Fractionation, Radiation; D005260:Female; D006801:Humans; D061089:Radiotherapy, Image-Guided; D012189:Retrospective Studies; D012867:Skin / Q000033:anatomy & histology; D016896:Treatment Outcome; D001743:Urinary Bladder / Q000473:pathology / Q000528:radiation effects; D001749:Urinary Bladder Neoplasms / Q000532:radiotherapy*