title: The reasons for discrepancies in target volume delineation : a SASRO study on head-and-neck and prostate cancers.
abstract: OBJECTIVE
  To understand the reasons for differences in the delineation of target volumes between physicians.
  
  
  METHODS
  18 Swiss radiooncology centers were invited to delineate volumes for one prostate and one head-and-neck case. In addition, a questionnaire was sent to evaluate the differences in the volume definition (GTV [gross tumor volume], CTV [clinical target volume], PTV [planning target volume]), the various estimated margins, and the nodes at risk. Coherence between drawn and stated margins by centers was calculated. The questionnaire also included a nonspecific series of questions regarding planning methods in each institution.
  
  
  RESULTS
  Fairly large differences in the drawn volumes were seen between the centers in both cases and also in the definition of volumes. Correlation between drawn and stated margins was fair in the prostate case and poor in the head-and-neck case. The questionnaire revealed important differences in the planning methods between centers.
  
  
  CONCLUSIONS
  These large differences could be explained by (1) a variable knowledge/interpretation of ICRU definitions, (2) variable interpretations of the potential microscopic extent, (3) difficulties in GTV identification, (4) differences in the concept, and (5) incoherence between theory (i.e., stated margins) and practice (i.e., drawn margins).
authors.affiliation: Department of Radiation Oncology, University Hospital of Lausanne, Lausanne, Switzerland.
authors.forename: Wendy
authors.initials: W
authors.lastname: Jeanneret-Sozzi
authors.forename: Raphaël
authors.initials: R
authors.lastname: Moeckli
authors.forename: Jean-François
authors.initials: JF
authors.lastname: Valley
authors.forename: Abderrahim
authors.initials: A
authors.lastname: Zouhair
authors.forename: Esat Mahmut
authors.initials: EM
authors.lastname: Ozsahin
authors.forename: René-Olivier
authors.initials: RO
authors.lastname: Mirimanoff
mesh_terms: D000230:Adenocarcinoma / Q000000981:diagnostic imaging / Q000473:pathology / Q000532:radiotherapy*; D000368:Aged; D016251:CD-ROM; D002294:Carcinoma, Squamous Cell / Q000000981:diagnostic imaging / Q000473:pathology / Q000532:radiotherapy*; D006258:Head and Neck Neoplasms / Q000000981:diagnostic imaging / Q000473:pathology / Q000532:radiotherapy*; D006801:Humans; D008198:Lymph Nodes / Q000473:pathology; D008297:Male; D009367:Neoplasm Staging; D015588:Observer Variation; D011467:Prostate / Q000473:pathology; D017430:Prostate-Specific Antigen / Q000097:blood; D011471:Prostatic Neoplasms / Q000097:blood / Q000000981:diagnostic imaging / Q000473:pathology / Q000532:radiotherapy*; D011880:Radiotherapy Planning, Computer-Assisted; D011795:Surveys and Questionnaires; D014057:Tomography, X-Ray Computed; D014059:Tongue / Q000473:pathology; D014062:Tongue Neoplasms / Q000000981:diagnostic imaging / Q000473:pathology / Q000532:radiotherapy*
chemical_list: D017430:Prostate-Specific Antigen