title: Harmonization of the Volume of Interest Delineation among All Eleven Radiotherapy Centers in the North of France.
abstract: BACKGROUND
  Inter-observer delineation variation has been detailed for many years in almost every tumor location. Inadequate delineation can impair the chance of cure and/or increase toxicity. The aim of our original work was to prospectively improve the homogeneity of delineation among all of the senior radiation oncologists in the Nord-Pas de Calais region, irrespective of the conditions of practice.
  
  
  METHODS
  All 11 centers were involved. The first studied cancer was prostate cancer. Three clinical cases were studied: a low-risk prostate cancer case (case 1), a high-risk prostate cancer case (pelvic nodes, case 2) and a case of post-operative biochemical elevated PSA (case 3). All of the involved physicians delineated characteristically the clinical target volume (CTV) and organs at risk. The volumes were compared using validated indexes: the volume ratio (VR), common and additional volumes (CV and AV), volume overlap (VO) and Dice similarity coefficient (DSC). A second delineation of the same three cases was performed after discussion of the slice results and the choice of shared guidelines to evaluate homogenization. A comparative analysis of the indexes before and after discussion was conducted using the Wilcoxon test for paired samples. A p-value less than 0.05 was considered to indicate statistical significance.
  
  
  RESULTS
  The indexes were not improved in case 1, for which the inter-observer agreement was considered good after the first comparison (DSC = 0.83 ± 0.06). In case 2, the second comparison showed homogenization of the CTV delineation with a significant improvement in CV (81.4 ± 11.7 vs. 88.6 ± 10.26, respectively, p = 0.048), VO (0.41 ± 0.09 vs. 0.47 ± 0.07, respectively; p = 0.009) and DSC (0.58 ± 0.09 vs. 0.63 ± 0.07, respectively; p = 0.0098). In case 3, VR and AV were significantly improved: VR: 1.71(± 0.6) vs. 1.34(± 0.46), respectively, p = 0.0034; AV: 46.58(± 14.50) vs. 38.08(± 15.10), respectively, p = 0.0024. DSC was not improved, but it was already superior to 0.6 in the first comparison.
  
  
  CONCLUSIONS
  Our prospective work showed that a collaborative discussion about clinical cases and the choice of shared guidelines within an established framework improved the homogeneity of CTV delineation among the senior radiation oncologists in our region.
authors.affiliation: Academic Radiation Oncology Department, Centre Oscar Lambret, Lille University, Lille, France.|CRISTAL, UMR CNRS 9189, Lille, France.
authors.forename: David
authors.initials: D
authors.lastname: Pasquier
authors.affiliation: Institut Andrée Dutreix, Dunkerque, France.
authors.forename: Laurence
authors.initials: L
authors.lastname: Boutaud de la Combe-Chossiere
authors.affiliation: Centre Léonard de Vinci, Dechy, France.
authors.forename: Damien
authors.initials: D
authors.lastname: Carlier
authors.affiliation: Centre Léonard de Vinci, Dechy, France.
authors.forename: Franck
authors.initials: F
authors.lastname: Darloy
authors.affiliation: Centre Joliot Curie, Boulogne sur mer, France.
authors.forename: Anne Catherine
authors.initials: AC
authors.lastname: Degrendel-Courtecuisse
authors.affiliation: Centre de Cancérologie Les Dentellières, Valenciennes, France.
authors.forename: Chantal
authors.initials: C
authors.lastname: Dufour
authors.affiliation: Centre Pierre Curie, Béthune, France.
authors.forename: Mustapha
authors.initials: M
authors.lastname: Fares
authors.affiliation: Centre Gray, Maubeuge, France.
authors.forename: Laurent
authors.initials: L
authors.lastname: Gilbeau
authors.affiliation: Academic Radiation Oncology Department, Centre Oscar Lambret, Lille University, Lille, France.
authors.forename: Xavier
authors.initials: X
authors.lastname: Liem
authors.affiliation: Centre Bourgogne Clinique du Bois, Lille, France.
authors.forename: Philippe
authors.initials: P
authors.lastname: Martin
authors.affiliation: Centre Gray, Maubeuge, France.
authors.forename: Pascal
authors.initials: P
authors.lastname: Meyer
authors.affiliation: Centre de Cancérologie Les Dentellières, Valenciennes, France.
authors.forename: Jean François
authors.initials: JF
authors.lastname: Minne
authors.affiliation: Centre Galilée, Lille, France.
authors.forename: Olimpia
authors.initials: O
authors.lastname: Olszyk
authors.affiliation: Centre Marie Curie, Arras, France.
authors.forename: Hassan
authors.initials: H
authors.lastname: Rhliouch
authors.affiliation: Centre de Cancérologie de l'Artois, Lens, France.
authors.forename: Marc
authors.initials: M
authors.lastname: Tokarski
authors.affiliation: Réseau Onco Nord Pas de Calais, Loos, France.
authors.forename: Chloé
authors.initials: C
authors.lastname: Viot
authors.affiliation: Academic Radiation Oncology Department, Centre Oscar Lambret, Lille University, Lille, France.
authors.forename: Bernard
authors.initials: B
authors.lastname: Castelain
authors.affiliation: Academic Radiation Oncology Department, Centre Oscar Lambret, Lille University, Lille, France.|CRISTAL, UMR CNRS 9189, Lille, France.
authors.forename: Eric
authors.initials: E
authors.lastname: Lartigau
mesh_terms: D005602:France; D006801:Humans; D008297:Male; D015588:Observer Variation; D011446:Prospective Studies; D011467:Prostate / Q000473:pathology* / Q000528:radiation effects*; D011471:Prostatic Neoplasms / Q000473:pathology* / Q000532:radiotherapy*; D011881:Radiotherapy, Computer-Assisted; D061089:Radiotherapy, Image-Guided