title: Dose-response relationships for an atomized symptom of fecal incontinence after gynecological radiotherapy.
abstract: OBJECTIVE
  The aim of this study was to investigate what bowel organ and delivered dose levels are most relevant for the development of 'emptying of all stools into clothing without forewarning' so that the related dose-responses could be derived as an aid in avoiding this distressing symptom in the future.
  
  
  METHODS
  Of the 77 gynecological cancer survivors treated with radiotherapy (RT) for gynecological cancer, 13 developed the symptom. The survivors were treated between 1991 and 2003. The anal-sphincter region, the rectum, the sigmoid and the small intestines were all delineated and the dose-volume histograms were exported for each patient. The dose-volume parameters were estimated fitting the data to the Relative Seriality (RS), the Lyman and the generalized Equivalent Uniform Dose (gEUD) model.
  
  
  RESULTS
  The dose-response parameters for all three models and four organs at risk (OARs) were estimated. The data from the sigmoid fits the studied models best: D50 was 58.8 and 59.5 Gy (RS, Lyman), γ50 was 1.60 and 1.57 (RS, Lyman), s was 0.32, n was 0.13 and a was 7.7 (RS, Lyman, gEUD). The estimated volume parameters indicate that the investigated OARs behave serially for this endpoint. Our results for the three models studied indicate that they have the same predictive power (similar LL values) for the symptom as a function of the dose for all investigated OARs.
  
  
  CONCLUSIONS
  In our study, the anal-sphincter region and sigmoid fit our data best, but all OARs were found to have steep dose-responses for 'emptying of all stools into clothing without forewarning' and thus, the outcome can be predicted with an NTCP model. In addition, the dose to the four studied OARs may be considered when minimizing the risk of the symptom.
authors.affiliation: Department of Oncology-Pathology, Division of Clinical Cancer Epidemiology, Karolinska Institutet, Stockholm, Sweden. Eleftheria.Alevronta@ki.se
authors.forename: Eleftheria
authors.initials: E
authors.lastname: Alevronta
authors.forename: Helena
authors.initials: H
authors.lastname: Lind
authors.forename: Massoud
authors.initials: M
authors.lastname: Al-Abany
authors.forename: Ann-Charlotte
authors.initials: AC
authors.lastname: Waldenström
authors.forename: Caroline
authors.initials: C
authors.lastname: Olsson
authors.forename: Gail
authors.initials: G
authors.lastname: Dunberger
authors.forename: Panayotis
authors.initials: P
authors.lastname: Mavroidis
authors.forename: Tommy
authors.initials: T
authors.lastname: Nyberg
authors.forename: Karl-Axel
authors.initials: KA
authors.lastname: Johansson
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Åvall-Lundqvist
authors.forename: Gunnar
authors.initials: G
authors.lastname: Steineck
authors.forename: Bengt K
authors.initials: BK
authors.lastname: Lind
mesh_terms: D000230:Adenocarcinoma / Q000453:epidemiology / Q000532:radiotherapy*; D000368:Aged; D001003:Anal Canal / Q000528:radiation effects; D004307:Dose-Response Relationship, Radiation; D005242:Fecal Incontinence / Q000453:epidemiology / Q000209:etiology*; D005260:Female; D005833:Genital Neoplasms, Female / Q000453:epidemiology / Q000532:radiotherapy*; D006801:Humans; D008875:Middle Aged; D058958:Organs at Risk / Q000528:radiation effects; D011832:Radiation Injuries / Q000453:epidemiology / Q000209:etiology*; D011879:Radiotherapy Dosage; D012007:Rectum / Q000528:radiation effects; D017741:Survivors / Q000706:statistics & numerical data; D016896:Treatment Outcome