title: Impact of intravenous contrast enhancement phase on target definition for hepatocellular carcinoma (HCC) and intrahepatic cholangiocarcinoma (IHC): Observations from patients enrolled on a prospective phase 2 trial.
abstract: BACKGROUND
  The safety and efficacy of radiation therapy for hepatocellular carcinoma (HCC) and intrahepatic cholangiocarcinoma (IHC) depend on accurate definition of gross tumor volume (GTV), but GTV often varies between phases of multiphasic computed tomography (CT) imaging.
  
  
  METHODS
  We contoured GTVs on arterial, portal venous, and delayed phases of multiphasic CT scans for 32 patients treated on an institutional review board-approved prospective trial of proton therapy for primary liver tumors and determined which phase provided optimal GTV visualization. We assessed agreement between individual phase GTVs to determine if GTV for each phase was encompassed in a 5-mm expansion of either the smallest or the best-visualized GTV.
  
  
  RESULTS
  There were 19 HCC lesions and 14 IHC lesions. HCC lesions were best identified on the arterial phase in 42% (n = 8), portal venous phase in 32% (n = 6), and delayed phase in 26% (n = 5). IHC lesions were best identified on portal venous phase in 64% (n = 9) and the arterial phase in 29% (n = 4), with 1 case equally visualized on arterial and portal venous phases. In all 33 lesions, a 5-mm expansion around the smallest GTV failed to cover GTVs defined on other available phases. A 5-mm expansion around the best-visualized GTV provided satisfactory coverage of all available phases' GTVs in 6/18 HCC cases and 2/9 IHC cases.
  
  
  CONCLUSIONS
  Variability between GTVs on multiphasic CT scans could not be overcome with a 5-mm expansion of either the smallest GTV or the best-visualized GTV. Assessment of all available intravenous contrast phases is essential to accurately define the GTV.
authors.affiliation: Department of Radiation Oncology, Mayo Clinic, Phoenix, Arizona.
authors.forename: Joshua R
authors.initials: JR
authors.lastname: Niska
authors.affiliation: Department of Radiation Oncology, Massachusetts General Hospital, Boston, Massachusetts.
authors.forename: Florence K
authors.initials: FK
authors.lastname: Keane
authors.affiliation: Department of Radiation Oncology, Massachusetts General Hospital, Boston, Massachusetts.
authors.forename: John A
authors.initials: JA
authors.lastname: Wolfgang
authors.affiliation: Department of Radiology, Massachusetts General Hospital, Boston, Massachusetts.
authors.forename: Peter F
authors.initials: PF
authors.lastname: Hahn
authors.affiliation: Department of Radiation Oncology, Massachusetts General Hospital, Boston, Massachusetts.
authors.forename: Jennifer Y
authors.initials: JY
authors.lastname: Wo
authors.affiliation: Department of Medicine, Division of Hematology-Oncology, Massachusetts General Hospital, Boston, Massachusetts.
authors.forename: Andrew X
authors.initials: AX
authors.lastname: Zhu
authors.affiliation: Department of Radiation Oncology, Massachusetts General Hospital, Boston, Massachusetts. Electronic address: tshong1@mgh.harvard.edu.
authors.forename: Theodore S
authors.initials: TS
authors.lastname: Hong
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001650:Bile Duct Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology / Q000532:radiotherapy; D006528:Carcinoma, Hepatocellular / Q000000981:diagnostic imaging* / Q000473:pathology / Q000532:radiotherapy; D018281:Cholangiocarcinoma / Q000000981:diagnostic imaging* / Q000473:pathology / Q000532:radiotherapy; D003287:Contrast Media / Q000008:administration & dosage*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007275:Injections, Intravenous; D008113:Liver Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology / Q000532:radiotherapy; D008297:Male; D008875:Middle Aged; D011379:Prognosis; D011446:Prospective Studies; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted; D014057:Tomography, X-Ray Computed; D047368:Tumor Burden
chemical_list: D003287:Contrast Media