title: Conformal radiotherapy planning of cervix carcinoma: differences in the delineation of the clinical target volume. A comparison between gynaecologic and radiation oncologists.
abstract: OBJECTIVE
  To assess uncertainties in the definition of the clinical target volume (CTV) for patients scheduled for primary radiotherapy of cervix carcinoma.
  
  
  METHODS
  Seven physicians (five radiation oncologists and two gynaecologists) independently contoured the CTVs for three patients. All observers were provided with the same clinical information. CTVs were entered directly in the treatment planning system. Differences were analysed qualitatively and quantitatively.
  
  
  RESULTS
  The qualitative analysis revealed a good agreement by all observers on anatomical structures identified to be at risk for tumour spread. Quantitatively, however, a large interobserver variability was found. The ratio between largest and smallest volumes ranged between 3.6 and 4.9 for all observers (3.6-4.9 for the radiation oncologists, 1.3-2.8 for the gynaecologists). The median three-dimensional difference in gravity centres ranged between 10.9 and 26.3mm for the respective patients. The ratio of common volumes to encompassing volumes ranged between 0.11 and 0.13 for the radiation oncologists, and between 0.30 and 0.57 for the gynaecologists.
  
  
  CONCLUSIONS
  Although there was a good consistency in outlined anatomical structures, for the radiation therapy of carcinomas of the uterine cervix a large interobserver variability in CTV delineation concerning the magnitude and relative location of volumes was observed. Compared to other factors, e.g. set-up and organ motion, interobserver variability in CTV definition seems to have the highest impact on the geometrical accuracy in the radiotherapy of this tumour entity.
authors.affiliation: Department of Radiotherapy, Klinik für Strahlentherapie, University of Goettingen, Robert-Koch-Strasse 40, Germany.
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Weiss
authors.forename: Susanne
authors.initials: S
authors.lastname: Richter
authors.forename: Thomas
authors.initials: T
authors.lastname: Krauss
authors.forename: Silke I
authors.initials: SI
authors.lastname: Metzelthin
authors.forename: Andrea
authors.initials: A
authors.lastname: Hille
authors.forename: Olivier
authors.initials: O
authors.lastname: Pradier
authors.forename: Birgit
authors.initials: B
authors.lastname: Siekmeyer
authors.forename: Hilke
authors.initials: H
authors.lastname: Vorwerk
authors.forename: Clemens F
authors.initials: CF
authors.lastname: Hess
mesh_terms: D000328:Adult; D000368:Aged; D000465:Algorithms; D000704:Analysis of Variance; D002277:Carcinoma / Q000473:pathology / Q000532:radiotherapy*; D005260:Female; D006801:Humans; D008875:Middle Aged; D011880:Radiotherapy Planning, Computer-Assisted; D020266:Radiotherapy, Conformal / Q000379:methods*; D002583:Uterine Cervical Neoplasms / Q000473:pathology / Q000532:radiotherapy*