title: Intraobserver and interobserver agreement in volumetric assessment of glioblastoma multiforme resection.
abstract: BACKGROUND
  The role of extent of tumor resection in improving outcome for patients with glioblastoma multiforme (GBM) is still under debate.
  
  
  OBJECTIVE
  To analyze intraobserver and interobserver agreement of manual segmentation as a method for volumetric assessment of GBM resection.
  
  
  METHODS
  Three observers performed volumetric assessment of preoperative tumor volume (PreTV) and postoperative tumor volume (PostTV) by manual segmentation on contrast-enhanced T1-weighted MRI data sets of 8 patients. Measurements were repeated after a minimum interval of 2 weeks. Intraobserver and interobserver agreement for PreTV, PostTV, and residual tumor volume (RTV) percentage were expressed in intraclass correlation coefficients (ICCs).
  
  
  RESULTS
  Intraobserver agreement is high for PreTV (ICC = 0.99), PostTV (ICC = 0.73-0.94), and RTV (ICC = 0.89-0.94). Interobserver agreement is high for PreTV (ICC = 0.97), but low for PostTV (ICC = 0.54) and RTV (ICC = 0.52).
  
  
  CONCLUSIONS
  Postoperative assessment of GBM volume seems to offer high intraobserver agreement, but low interobserver agreement. Using absolute RTV values to relate extent of tumor resection with survival may be unreliable. More research is needed before this method can be used as a valid end point for clinical studies. Computer-assisted tumor volume calculation may increase interobserver agreement in the future.
authors.affiliation: Department of Neurosurgery, Maastricht University Medical Center, Maastricht, The Netherlands. pieter@kubben.nl
authors.forename: Pieter L
authors.initials: PL
authors.lastname: Kubben
authors.forename: Alida A
authors.initials: AA
authors.lastname: Postma
authors.forename: Alfons G H
authors.initials: AG
authors.lastname: Kessels
authors.forename: Jacobus J
authors.initials: JJ
authors.lastname: van Overbeeke
authors.forename: Henk
authors.initials: H
authors.lastname: van Santbrink
mesh_terms: D000368:Aged; D001932:Brain Neoplasms / Q000473:pathology* / Q000601:surgery*; D005260:Female; D005909:Glioblastoma / Q000473:pathology* / Q000601:surgery*; D006801:Humans; D021621:Imaging, Three-Dimensional; D008279:Magnetic Resonance Imaging; D008297:Male; D015588:Observer Variation; D011379:Prognosis; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D016896:Treatment Outcome