title: Measurement of lung tumor volumes using three-dimensional computer planning software.
abstract: OBJECTIVE
  To examine the interclinician variation in the definition of gross tumor volume (GTV) in patients undergoing radiotherapy for non-small-cell lung cancer (NSCLC), develop methods to minimize this variation, and test these methods.
  
  
  METHODS
  The radiotherapy planning computed tomography (CT) scans of 6 consecutive patients with NSCLC in which the radiologist was able to define and outline the GTV were used. Six oncologists independently contoured the tumors with the radiologist's markings as a guide using a three-dimensional treatment planning system. Separate contours were prepared using only mediastinal window settings and using both mediastinal and lung window settings. The volumes were calculated using the planning system software (series 1). Factors that resulted in interclinician variation were determined, and, after a 3-year interval, 5 of the 6 clinicians redefined the GTVs using a revised protocol aimed at minimizing variation (series 2).
  
  
  RESULTS
  For series 1, the interclinician variation in the measurement of volumes ranged from 5%, in the most tightly measured tumor, to 42%, in the most variable, but was, on average, 20%. Statistically significant differences were noted among the clinicians (p = 0.002), that is, some clinicians tended to record relatively small and some relatively large volumes. The reasons for the variation among the oncologists included a tendency to include regions with a low probability of containing tumor, as if the oncologist were contouring a target volume; inclusion of adjacent atelectasis (ignoring the radiologist's outline); and variable treatment of spicules. When the exercise was repeated using the revised protocol (series 2), the degree of interclinician variation was reduced, with a range of 7-22% (average 13%). In series 2, the differences among the clinicians were not statistically significant (p = 0.25).
  
  
  CONCLUSIONS
  Despite major radiologic input, significant variation occurred in the delineation of the three-dimensional GTVs of NSCLC among oncologists. Standardization of the approach with guidelines resulted in a reduction in this variation.
authors.affiliation: Division of Radiation Oncology, Peter MacCallum Cancer Institute, A'Beckett Street, Melbourne, Victoria 8006, Australia.
authors.forename: Patrick
authors.initials: P
authors.lastname: Bowden
authors.forename: Richard
authors.initials: R
authors.lastname: Fisher
authors.forename: Michael
authors.initials: M
authors.lastname: Mac Manus
authors.forename: Andrew
authors.initials: A
authors.lastname: Wirth
authors.forename: Gillian
authors.initials: G
authors.lastname: Duchesne
authors.forename: Michael
authors.initials: M
authors.lastname: Millward
authors.forename: Allan
authors.initials: A
authors.lastname: McKenzie
authors.forename: Judy
authors.initials: J
authors.lastname: Andrews
authors.forename: David
authors.initials: D
authors.lastname: Ball
mesh_terms: D000704:Analysis of Variance; D002289:Carcinoma, Non-Small-Cell Lung / Q000000981:diagnostic imaging* / Q000532:radiotherapy; D006801:Humans; D021621:Imaging, Three-Dimensional; D008175:Lung Neoplasms / Q000000981:diagnostic imaging* / Q000532:radiotherapy; D015588:Observer Variation; D014057:Tomography, X-Ray Computed