title: Adaptive radiotherapy for invasive bladder cancer: a feasibility study.
abstract: OBJECTIVE
  To evaluate the feasibility of adaptive radiotherapy (ART) in combination with a partial bladder irradiation.
  
  
  METHODS
  Twenty-one patients with solitary T1-T4 N0M0 bladder cancer were treated to the bladder tumor + 2 cm margin planning target volume (PTV(CONV)). During the first treatment week, five daily computed tomography (CT) scans were made immediately before or after treatment. In the second week, a volume was constructed encompassing the gross tumor volumes (GTVs) on the planning scan and the five CT scans (GTV(ART)). The GTV(ART) was expanded with a 1 cm margin for the construction of a PTV(ART). Starting in the third week, patients were treated to PTV(ART). Repeat CT scans were used to evaluate treatment accuracy.
  
  
  RESULTS
  On 5 of 91 repeat CT scans (5%), the GTV was not adequately covered by the PTV(ART). On treatment planning, there was only one scan in which the GTV was not adequately covered by the 95% isodose. On average, the treatment volumes were reduced by 40% when comparing PTV(ART) with PTV(CONV) (p < 0.0001).
  
  
  CONCLUSIONS
  The adaptive strategy for bladder cancer is an effective way to deal with treatment errors caused by variations in bladder tumor position and leads to a substantial reduction in treatment volumes.
authors.affiliation: Department of Radiation Oncology, The Netherlands Cancer Institute-Antoni van Leeuwenhoek Hospital, Amsterdam, The Netherlands. f.pos@nki.nl
authors.forename: Floris J
authors.initials: FJ
authors.lastname: Pos
authors.forename: Maarten
authors.initials: M
authors.lastname: Hulshof
authors.forename: Joos
authors.initials: J
authors.lastname: Lebesque
authors.forename: Heidi
authors.initials: H
authors.lastname: Lotz
authors.forename: Geertjan
authors.initials: G
authors.lastname: van Tienhoven
authors.forename: Luc
authors.initials: L
authors.lastname: Moonen
authors.forename: Peter
authors.initials: P
authors.lastname: Remeijer
mesh_terms: D005240:Feasibility Studies; D006801:Humans; D009068:Movement; D009367:Neoplasm Staging; D011878:Radiotherapy / Q000379:methods; D011880:Radiotherapy Planning, Computer-Assisted; D014057:Tomography, X-Ray Computed; D001743:Urinary Bladder / Q000033:anatomy & histology / Q000000981:diagnostic imaging; D001749:Urinary Bladder Neoplasms / Q000000981:diagnostic imaging / Q000473:pathology / Q000532:radiotherapy*