title: Differences in delineation guidelines for head and neck cancer result in inconsistent reported dose and corresponding NTCP.
abstract: OBJECTIVE
  To test the hypothesis that delineation of swallowing organs at risk (SWOARs) based on different guidelines results in differences in dose-volume parameters and subsequent normal tissue complication probability (NTCP) values for dysphagia-related endpoints.
  
  
  METHODS
  Nine different SWOARs were delineated according to five different delineation guidelines in 29 patients. Reference delineation was performed according to the guidelines and NTCP-models of Christianen et al. Concordance Index (CI), dosimetric consequences, as well as differences in the subsequent NTCPs were calculated.
  
  
  RESULTS
  The median CI of the different delineation guidelines with the reference guidelines was 0.54 for the pharyngeal constrictor muscles, 0.56 for the laryngeal structures and 0.07 for the cricopharyngeal muscle and esophageal inlet muscle. The average difference in mean dose to the SWOARs between the guidelines with the largest difference (maxΔD) was 3.5±3.2Gy. A mean ΔNTCP of 2.3±2.7% was found. For two patients, ΔNTCP exceeded 10%.
  
  
  CONCLUSIONS
  The majority of the patients showed little differences in NTCPs between the different delineation guidelines. However, large NTCP differences >10% were found in 7% of the patients. For correct use of NTCP models in individual patients, uniform delineation guidelines are of great importance.
authors.affiliation: University of Groningen, University Medical Center Groningen, Department of Radiation Oncology, Groningen, The Netherlands. Electronic address: c.l.brouwer@umcg.nl.
authors.forename: Charlotte L
authors.initials: CL
authors.lastname: Brouwer
authors.affiliation: University of Groningen, University Medical Center Groningen, Department of Radiation Oncology, Groningen, The Netherlands.
authors.forename: Roel J H M
authors.initials: RJ
authors.lastname: Steenbakkers
authors.affiliation: University of Groningen, University Medical Center Groningen, Department of Radiation Oncology, Groningen, The Netherlands.
authors.forename: Elske
authors.initials: E
authors.lastname: Gort
authors.affiliation: University of Groningen, University Medical Center Groningen, Department of Radiation Oncology, Groningen, The Netherlands.
authors.forename: Marije E
authors.initials: ME
authors.lastname: Kamphuis
authors.affiliation: University of Groningen, University Medical Center Groningen, Department of Radiation Oncology, Groningen, The Netherlands.
authors.forename: Hans Paul
authors.initials: HP
authors.lastname: van der Laan
authors.affiliation: University of Groningen, University Medical Center Groningen, Department of Radiation Oncology, Groningen, The Netherlands.
authors.forename: Aart A
authors.initials: AA
authors.lastname: Van't Veld
authors.affiliation: University of Groningen, University Medical Center Groningen, Department of Radiation Oncology, Groningen, The Netherlands.
authors.forename: Nanna M
authors.initials: NM
authors.lastname: Sijtsema
authors.affiliation: University of Groningen, University Medical Center Groningen, Department of Radiation Oncology, Groningen, The Netherlands.
authors.forename: Johannes A
authors.initials: JA
authors.lastname: Langendijk
mesh_terms: D000328:Adult; D000368:Aged; D003679:Deglutition / Q000502:physiology / Q000528:radiation effects; D003680:Deglutition Disorders / Q000209:etiology* / Q000517:prevention & control*; D004307:Dose-Response Relationship, Radiation; D005260:Female; D006258:Head and Neck Neoplasms / Q000473:pathology / Q000503:physiopathology / Q000532:radiotherapy*; D006801:Humans; D008297:Male; D008875:Middle Aged; D058958:Organs at Risk; D010609:Pharyngeal Muscles / Q000033:anatomy & histology / Q000503:physiopathology / Q000528:radiation effects; D017410:Practice Guidelines as Topic; D011336:Probability; D011832:Radiation Injuries / Q000209:etiology* / Q000517:prevention & control*; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods* / Q000592:standards*; D055815:Young Adult
keywords: Delineation guidelines; Head and neck; Interobserver variability; NTCP