title: Prediction of rectum and bladder morbidity following radiotherapy of prostate cancer based on motion-inclusive dose distributions.
abstract: OBJECTIVE
  In radiotherapy (RT) of prostate cancer the key organs at risk (ORs) - the rectum and the bladder - display considerable motion, which may influence the dose/volume parameters predicting for morbidity. In this study we compare motion-inclusive doses to planned doses for the rectum and bladder and explore their associations with prospectively recorded morbidity.
  
  
  METHODS
  The study included 38 prostate cancer patients treated with hypo-fractionated image-guided intensity-modulated RT that had an average of nine repeat CT scans acquired during treatment. These scans were registered to the respective treatment planning CT (pCT) followed by a new dose calculation from which motion-inclusive dose distributions were derived. The pCT volumes, the treatment course averaged volumes as well as the planned and motion-inclusive doses were associated with acute and late morbidity (morbidity cut-off: ≥ Grade 2).
  
  
  RESULTS
  Acute rectal morbidity (observed in 29% of cases) was significantly associated with both smaller treatment course averaged rectal volumes (population median: 75 vs. 94 cm(3)) and the motion-inclusive volume receiving doses close to the prescription dose (2 Gy-equivalent dose of 76 Gy).
  
  
  CONCLUSIONS
  Variation in rectum and bladder volumes leads to deviations between planned and delivered dose/volume parameters that should be accounted for to improve the ability to predict morbidity following RT.
authors.affiliation: Department of Medical Physics, Aarhus University Hospital, Aarhus, Denmark. mariator@rm.dk
authors.forename: Maria
authors.initials: M
authors.lastname: Thor
authors.forename: Lise
authors.initials: L
authors.lastname: Bentzen
authors.forename: Liv B
authors.initials: LB
authors.lastname: Hysing
authors.forename: Christian
authors.initials: C
authors.lastname: Ekanger
authors.forename: Svein-Inge
authors.initials: SI
authors.lastname: Helle
authors.forename: Ása
authors.initials: Á
authors.lastname: Karlsdóttir
authors.forename: Ludvig Paul
authors.initials: LP
authors.lastname: Muren
mesh_terms: D000368:Aged; D006801:Humans; D008297:Male; D008875:Middle Aged; D009038:Motion; D011471:Prostatic Neoplasms / Q000532:radiotherapy*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted; D012007:Rectum / Q000528:radiation effects*; D001743:Urinary Bladder / Q000528:radiation effects*