title: Interobserver delineation uncertainty in involved-node radiation therapy (INRT) for early-stage Hodgkin lymphoma: on behalf of the Radiotherapy Committee of the EORTC lymphoma group.
abstract: OBJECTIVE
  In early-stage classical Hodgkin lymphoma (HL) the target volume nowadays consists of the volume of the originally involved nodes. Delineation of this volume on a post-chemotherapy CT-scan is challenging. We report on the interobserver variability in target volume definition and its impact on resulting treatment plans.
  
  
  METHODS
  Two representative cases were selected (1: male, stage IB, localization: left axilla; 2: female, stage IIB, localizations: mediastinum and bilateral neck). Eight experienced observers individually defined the clinical target volume (CTV) using involved-node radiotherapy (INRT) as defined by the EORTC-GELA guidelines for the H10 trial. A consensus contour was generated and the standard deviation computed. We investigated the overlap between observer and consensus contour [Sørensen-Dice coefficient (DSC)] and the magnitude of gross deviations between the surfaces of the observer and consensus contour (Hausdorff distance). 3D-conformal (3D-CRT) and intensity-modulated radiotherapy (IMRT) plans were calculated for each contour in order to investigate the impact of interobserver variability on each treatment modality. Similar target coverage was enforced for all plans.
  
  
  RESULTS
  The median CTV was 120 cm3(IQR: 95-173 cm3) for Case 1, and 255 cm3(IQR: 183-293 cm3) for Case 2. DSC values were generally high (>0.7), and Hausdorff distances were about 30 mm. The SDs between all observer contours, providing an estimate of the systematic error associated with delineation uncertainty, ranged from 1.9 to 3.8 mm (median: 3.2 mm). Variations in mean dose resulting from different observer contours were small and were not higher in IMRT plans than in 3D-CRT plans.
  
  
  CONCLUSIONS
  We observed considerable differences in target volume delineation, but the systematic delineation uncertainty of around 3 mm is comparable to that reported in other tumour sites. This report is a first step towards calculating an evidence-based planning target volume margin for INRT in HL.
authors.affiliation: a Department of Oncology, Section of Radiotherapy, Rigshospitalet , University of Copenhagen , Copenhagen, Denmark.
authors.forename: Marianne C
authors.initials: MC
authors.lastname: Aznar
authors.affiliation: b Service de Radiothérapie Oncologique , Institut Gustave Roussy , Villejuif , France.
authors.forename: Theodore
authors.initials: T
authors.lastname: Girinsky
authors.affiliation: a Department of Oncology, Section of Radiotherapy, Rigshospitalet , University of Copenhagen , Copenhagen, Denmark.
authors.forename: Anne Kiil
authors.initials: AK
authors.lastname: Berthelsen
authors.affiliation: c Department of Radiotherapy , The Netherlands Cancer Institute , Amsterdam , The Netherlands.
authors.forename: Berthe
authors.initials: B
authors.lastname: Aleman
authors.affiliation: d Department of Radiation Oncology , University of Groningen, University Medical Center Groningen , Groningen , The Netherlands.
authors.forename: Max
authors.initials: M
authors.lastname: Beijert
authors.affiliation: e Department of Haematology, Rigshospitalet , University of Copenhagen , Copenhagen, Denmark.
authors.forename: Martin
authors.initials: M
authors.lastname: Hutchings
authors.affiliation: f Department of Radiation Oncology , Ghent University Hospital , Ghent , Belgium.
authors.forename: Yolande
authors.initials: Y
authors.lastname: Lievens
authors.affiliation: g Department of Radiation Oncology GZA, Iridium Cancer Network , University of Antwerp , Antwerp , Belgium.
authors.forename: Paul
authors.initials: P
authors.lastname: Meijnders
authors.affiliation: a Department of Oncology, Section of Radiotherapy, Rigshospitalet , University of Copenhagen , Copenhagen, Denmark.|e Department of Haematology, Rigshospitalet , University of Copenhagen , Copenhagen, Denmark.
authors.forename: Peter
authors.initials: P
authors.lastname: Meidahl Petersen
authors.affiliation: a Department of Oncology, Section of Radiotherapy, Rigshospitalet , University of Copenhagen , Copenhagen, Denmark.
authors.forename: Deborah
authors.initials: D
authors.lastname: Schut
authors.affiliation: a Department of Oncology, Section of Radiotherapy, Rigshospitalet , University of Copenhagen , Copenhagen, Denmark.
authors.forename: Maja V
authors.initials: MV
authors.lastname: Maraldo
authors.affiliation: h Department of Radiotherapy , Radboud University Medical Center , Nijmegen , The Netherlands.
authors.forename: Richard
authors.initials: R
authors.lastname: van der Maazen
authors.affiliation: a Department of Oncology, Section of Radiotherapy, Rigshospitalet , University of Copenhagen , Copenhagen, Denmark.|e Department of Haematology, Rigshospitalet , University of Copenhagen , Copenhagen, Denmark.
authors.forename: Lena
authors.initials: L
authors.lastname: Specht
mesh_terms: D005260:Female; D006689:Hodgkin Disease / Q000473:pathology* / Q000532:radiotherapy*; D006801:Humans; D015182:Lymphatic Irradiation / Q000379:methods*; D008297:Male; D015588:Observer Variation; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D020266:Radiotherapy, Conformal / Q000379:methods; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods; D035501:Uncertainty