title: Interobserver variability in target definition for hepatocellular carcinoma with and without portal vein thrombus: radiation therapy oncology group consensus guidelines.
abstract: OBJECTIVE
  Defining hepatocellular carcinoma (HCC) gross tumor volume (GTV) requires multimodal imaging, acquired in different perfusion phases. The purposes of this study were to evaluate the variability in contouring and to establish guidelines and educational recommendations for reproducible HCC contouring for treatment planning.
  
  
  METHODS
  Anonymous, multiphasic planning computed tomography scans obtained from 3 patients with HCC were identified and distributed to a panel of 11 gastrointestinal radiation oncologists. Panelists were asked the number of HCC cases they treated in the past year. Case 1 had no vascular involvement, case 2 had extensive portal vein involvement, and case 3 had minor branched portal vein involvement. The agreement between the contoured total GTVs (primary + vascular GTV) was assessed using the generalized kappa statistic. Agreement interpretation was evaluated using Landis and Koch's interpretation of strength of agreement. The S95 contour, defined using the simultaneous truth and performance level estimation (STAPLE) algorithm consensus at the 95% confidence level, was created for each case.
  
  
  RESULTS
  Of the 11 panelists, 3 had treated >25 cases in the past year, 2 had treated 10 to 25 cases, 2 had treated 5 to 10 cases, 2 had treated 1 to 5 cases, 1 had treated 0 cases, and 1 did not respond. Near perfect agreement was seen for case 1, and substantial agreement was seen for cases 2 and 3. For case 2, there was significant heterogeneity in the volume identified as tumor thrombus (range 0.58-40.45 cc). For case 3, 2 panelists did not include the branched portal vein thrombus, and 7 panelists contoured thrombus separately from the primary tumor, also showing significant heterogeneity in volume of tumor thrombus (range 4.52-34.27 cc).
  
  
  CONCLUSIONS
  In a group of experts, excellent agreement was seen in contouring total GTV. Heterogeneity exists in the definition of portal vein thrombus that may impact treatment planning, especially if differential dosing is contemplated. Guidelines for HCC GTV contouring are recommended.
authors: Department of Radiation Oncology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts. Electronic address: tshong1@mgh.harvard.edu.
authors: Theodore S
authors: TS
authors: Hong
authors: Department of Radiation Oncology, Washington University in St. Louis School of Medicine, St. Louis, Missouri.
authors: Walter R
authors: WR
authors: Bosch
authors: Department of Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, Texas.
authors: Sunil
authors: S
authors: Krishnan
authors: Department of Medical Imaging, University Health Network, Mount Sinai Hospital and Women's College Hospital, University of Toronto, Toronto, Ontario, Canada.
authors: Tae K
authors: TK
authors: Kim
authors: Department of Radiation Oncology, Dana-Farber Cancer Institute/Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts.
authors: Harvey J
authors: HJ
authors: Mamon
authors: Department of Radiology, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts.
authors: Paul
authors: P
authors: Shyn
authors: Department of Radiation Oncology, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania.
authors: Edgar
authors: E
authors: Ben-Josef
authors: Department of Radiation Oncology, Yonsei University Medical College, Seoul, Korea.
authors: Jinsil
authors: J
authors: Seong
authors: Department of Radiation Oncology, Mayo Clinic, Rochester, Minnesota.
authors: Michael G
authors: MG
authors: Haddock
authors: Department of Oncology, National Taiwan University Hospital, Taipei, Taiwan.
authors: Jason C
authors: JC
authors: Cheng
authors: Department of Radiation Oncology, University of Michigan Health System, Ann Arbor, Michigan.
authors: Mary U
authors: MU
authors: Feng
authors: Department of Radiation Oncology, Cleveland Clinic, Cleveland, Ohio.
authors: Kevin L
authors: KL
authors: Stephans
authors: Department of Radiation Oncology, Montreal General Hospital/McGill University Health Centre, Montreal, Quebec, Canada.
authors: David
authors: D
authors: Roberge
authors: Department of Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, Texas.
authors: Christopher
authors: C
authors: Crane
authors: Department of Radiation Oncology, Princess Margaret Cancer Centre/University of Toronto, Toronto, Ontario, Canada.
authors: Laura A
authors: LA
authors: Dawson
mesh_terms: D000368:Aged; D000465:Algorithms; D006528:Carcinoma, Hepatocellular / Q000098:blood supply / Q000175:diagnosis* / Q000000981:diagnostic imaging; D032921:Consensus; D005260:Female; D006801:Humans; D008113:Liver Neoplasms / Q000098:blood supply / Q000175:diagnosis* / Q000000981:diagnostic imaging; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D064847:Multimodal Imaging / Q000379:methods; D015588:Observer Variation; D011169:Portal Vein / Q000000981:diagnostic imaging; D015203:Reproducibility of Results; D014057:Tomography, X-Ray Computed; D047368:Tumor Burden; D035501:Uncertainty; D020246:Venous Thrombosis / Q000175:diagnosis* / Q000000981:diagnostic imaging