title: Parametrized rectal dose and associations with late toxicity in prostate cancer radiotherapy.
abstract: OBJECTIVE
  We investigated possible associations between planned dose-volume parameters and rectal late toxicity in 170 patients having radical prostate cancer radiotherapy.
  
  
  METHODS
  For each patient, the rectum was outlined from anorectal junction to sigmoid colon, and rectal dose was parametrized using dose-volume (DVH), dose-surface (DSH) and dose-line (DLH) histograms. Generation of DLHs differed from previous studies in that the rectal dose was parametrized without first unwrapping onto 2-dimensional dose-surface maps. Patient-reported outcomes were collected using a validated Later Effects in Normal Tissues Subjective, Objective, Management and Analytic questionnaire. Associations between dose and toxicity were assessed using a one-sided Mann-Whitney U test.
  
  
  RESULTS
  Associations (p < 0.05) were found between equieffective dose (EQD23) and late toxicity as follows: overall toxicity with DVH and DSH at 13-24 Gy; proctitis with DVH and DSH at 25-36 Gy and with DVH, DSH and DLH at 61-67 Gy; bowel urgency with DVH and DSH at 10-20 Gy. None of these associations met statistical significance following the application of a Bonferroni correction.
  
  
  CONCLUSIONS
  Independently confirmed associations between rectal dose and late toxicity remain elusive. Future work to increase the accuracy of the knowledge of the rectal dose, either by accounting for interfraction and intrafraction rectal motion or via stabilization of the rectum during treatment, may be necessary to allow for improved dose-toxicity comparisons.
  
  
  CONCLUSIONS
  This study is the first to use parametrized DLHs to study associations with patient-reported toxicity for prostate radiotherapy showing that it is feasible to model rectal dose mapping in three dimensions.
authors.affiliation: 1 Manchester Academic Health Science Centre (MAHSC), Faculty of Medical and Human Sciences, University of Manchester, Manchester, UK.|2 Christie Medical Physics and Engineering, The Christie NHS Foundation Trust, Manchester, UK.
authors.forename: Lynsey J
authors.identifier: http://orcid.org/0000-0002-3045-4885
authors.initials: LJ
authors.lastname: Hamlett
authors.affiliation: 3 Department of Oncology, The Christie NHS Foundation Trust, Manchester, UK.
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: McPartlin
authors.affiliation: 4 Oxford University Clinical Academic Graduate School, Medical Sciences Division, John Radcliffe Hospital, Oxford, UK.
authors.forename: Edward J
authors.initials: EJ
authors.lastname: Maile
authors.affiliation: 5 Hall-Edwards Radiotherapy Research Group, Medical Physics, Queen Elizabeth Hospital, University Hospital Birmingham NHS Foundation Trust, Birmingham, UK.
authors.forename: Gareth
authors.initials: G
authors.lastname: Webster
authors.affiliation: 6 The Christie NHS Foundation Trust, Manchester, UK.
authors.forename: Ric
authors.initials: R
authors.lastname: Swindell
authors.affiliation: 7 Department of Medical Physics, Clatterbridge Cancer Centre, Liverpool, UK.
authors.forename: Carl G
authors.initials: CG
authors.lastname: Rowbottom
authors.affiliation: 1 Manchester Academic Health Science Centre (MAHSC), Faculty of Medical and Human Sciences, University of Manchester, Manchester, UK.|3 Department of Oncology, The Christie NHS Foundation Trust, Manchester, UK.
authors.forename: Ananya
authors.initials: A
authors.lastname: Choudhury
authors.affiliation: 1 Manchester Academic Health Science Centre (MAHSC), Faculty of Medical and Human Sciences, University of Manchester, Manchester, UK.|2 Christie Medical Physics and Engineering, The Christie NHS Foundation Trust, Manchester, UK.
authors.forename: Adam H
authors.initials: AH
authors.lastname: Aitkenhead
mesh_terms: D000368:Aged; D004307:Dose-Response Relationship, Radiation; D006801:Humans; D008297:Male; D008875:Middle Aged; D011471:Prostatic Neoplasms / Q000532:radiotherapy*; D011832:Radiation Injuries / Q000517:prevention & control*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D012007:Rectum / Q000528:radiation effects*