title: Evaluation of delivered dose for a clinical daily adaptive plan selection strategy for bladder cancer radiotherapy.
abstract: OBJECTIVE
  To account for variable bladder size during bladder cancer radiotherapy, a daily plan selection strategy was implemented. The aim of this study was to calculate the actually delivered dose using an adaptive strategy, compared to a non-adaptive approach.
  
  
  METHODS
  Ten patients were treated to the bladder and lymph nodes with an adaptive full bladder strategy. Interpolated delineations of bladder and tumor on a full and empty bladder CT scan resulted in five PTVs for which VMAT plans were created. Daily cone beam CT (CBCT) scans were used for plan selection. Bowel, rectum and target volumes were delineated on these CBCTs, and delivered dose for these was calculated using both the adaptive plan, and a non-adaptive plan.
  
  
  RESULTS
  Target coverage for lymph nodes improved using an adaptive strategy. The full bladder strategy spared the healthy part of the bladder from a high dose. Average bowel cavity V30Gy and V40Gy significantly reduced with 60 and 69ml, respectively (p<0.01). Other parameters for bowel and rectum remained unchanged.
  
  
  CONCLUSIONS
  Daily plan selection compared to a non-adaptive strategy yielded similar bladder coverage and improved coverage for lymph nodes, with a significant reduction in bowel cavity V30Gy and V40Gy only, while other sparing was limited.
authors.affiliation: Department of Radiation Oncology, Academic Medical Center, Amsterdam, The Netherlands. Electronic address: l.j.lutkenhaus@amc.uva.nl.
authors.forename: Lotte J
authors.initials: LJ
authors.lastname: Lutkenhaus
authors.affiliation: Department of Radiation Oncology, Academic Medical Center, Amsterdam, The Netherlands.
authors.forename: Jorrit
authors.initials: J
authors.lastname: Visser
authors.affiliation: Department of Radiation Oncology, Academic Medical Center, Amsterdam, The Netherlands.
authors.forename: Rianne
authors.initials: R
authors.lastname: de Jong
authors.affiliation: Department of Radiation Oncology, Academic Medical Center, Amsterdam, The Netherlands.
authors.forename: Maarten C C M
authors.initials: MC
authors.lastname: Hulshof
authors.affiliation: Department of Radiation Oncology, Academic Medical Center, Amsterdam, The Netherlands.
authors.forename: Arjan
authors.initials: A
authors.lastname: Bel
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006801:Humans; D008297:Male; D011829:Radiation Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods; D012007:Rectum / Q000000981:diagnostic imaging; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed / Q000379:methods; D001749:Urinary Bladder Neoplasms / Q000532:radiotherapy*
keywords: Adaptive radiotherapy; Bladder cancer; Normal tissue sparing; Plan of the day; Plan selection