title: Reducing interobserver variation of boost-CTV delineation in breast conserving radiation therapy using a pre-operative CT and delineation guidelines.
abstract: OBJECTIVE
  To investigate whether using a pre-operative CT scan (Preop-CT) (1) decreases interobserver variation of boost-CTV delineation in breast conserving therapy (BCT), and (2) influences the size of the delineated volumes.
  
  
  METHODS
  Thirty cT1-2N0-1 breast cancer patients underwent a CT-scan in radiation treatment position, prior to and after lumpectomy. Five observers delineated a boost-CTV, both with and without access to the Preop-CT. For each patient and for each observer pair, the conformity index (CI) and the distance between the centres of mass (COMd) for both boost volumes were calculated. In addition, all delineated volumes including the standard deviation (SD) with respect to the median delineation were calculated.
  
  
  RESULTS
  Using a Preop-CT reduced the mean COMd of the boost-CTV from 1.1cm to 1.0 cm (p<0.001). No effect was seen on the CI, but the boost-CTV volume reduced from 42 cc to 36 cc (p=0.005), implying a reduction of interobserver variation. We saw no significant change in the SD.
  
  
  CONCLUSIONS
  Use of a Preop-CT in BCT results in a modest but statistically significant reduction in interobserver variation of the boost-CTV delineations and in a significant reduction in the boost-CTV volume.
authors.affiliation: Maastricht University Medical Centre, Department of Radiation Oncology (MAASTRO Clinic), The Netherlands. liesbeth.boersma@maastro.nl
authors.forename: Liesbeth J
authors.initials: LJ
authors.lastname: Boersma
authors.forename: Tomas
authors.initials: T
authors.lastname: Janssen
authors.forename: Paula H M
authors.initials: PH
authors.lastname: Elkhuizen
authors.forename: Philip
authors.initials: P
authors.lastname: Poortmans
authors.forename: Maurice
authors.initials: M
authors.lastname: van der Sangen
authors.forename: Astrid N
authors.initials: AN
authors.lastname: Scholten
authors.forename: Bianca
authors.initials: B
authors.lastname: Hanbeukers
authors.forename: Joop C
authors.initials: JC
authors.lastname: Duppen
authors.forename: Coen
authors.initials: C
authors.lastname: Hurkmans
authors.forename: Corine
authors.initials: C
authors.lastname: van Vliet
mesh_terms: D000328:Adult; D000368:Aged; D001943:Breast Neoplasms / Q000532:radiotherapy*; D005260:Female; D006801:Humans; D008875:Middle Aged; D015588:Observer Variation; D061089:Radiotherapy, Image-Guided; D014057:Tomography, X-Ray Computed / Q000379:methods*; D047368:Tumor Burden