title: The impact of (18)FDG-PET on target and critical organs in CT-based treatment planning of patients with poorly defined non-small-cell lung carcinoma: a prospective study.
abstract: OBJECTIVE
  To prospectively study the impact of coregistering (18)F-fluoro-deoxy-2-glucose hybrid positron emission tomographic (FDG-PET) images with CT images on the planning target volume (PTV), target coverage, and critical organ dose in radiation therapy planning of non-small-cell lung carcinoma.
  
  
  METHODS
  Thirty patients with poorly defined tumors on CT, referred for radical radiation therapy, underwent both FDG-PET and CT simulation procedures on the same day, in radiation treatment position. Image sets were coregistered using external fiducial markers. Three radiation oncologists independently defined the gross tumor volumes, using first CT data alone and then coregistered CT and FDG-PET data. Standard margins were applied to each gross tumor volume to generate a PTV, and standardized treatment plans were designed and calculated for each PTV. Dose-volume histograms were used to evaluate the relative effect of FDG information on target coverage and on normal tissue dose.
  
  
  RESULTS
  In 7 of 30 (23%) cases, FDG-PET information changed management strategy from radical to palliative. In 5 of the remaining 23 (22%) cases, new FDG-avid nodes were found within 5 cm of the primary tumor and were included in the PTV. The PTV defined using coregistered CT and FDG-PET would have been poorly covered by the CT-based treatment plan in 17--29% of cases, depending on the physician, implying a geographic miss had only CT information been available. The effect of FDG-PET on target definition varied with the physician, leading to a reduction in PTV in 24-70% of cases and an increase in 30-76% of cases. The relative change in PTV ranged from 0.40 to 1.86. On average, FDG-PET information led to a reduction in spinal cord dose but not in total lung dose, although large differences in dose to the lung were seen for a few individuals.
  
  
  CONCLUSIONS
  The coregistration of planning CT and FDG-PET images made significant alterations to patient management and to the PTV. Ultimately, changes to the PTV resulted in changes to the radiation treatment plans for the majority of cases. Where possible, we would recommend that FDG-PET data be integrated into treatment planning of non-small-cell lung carcinoma, particularly for three-dimensional conformal techniques.
authors.affiliation: Department of Medical Physics, Toronto-Sunnybrook Regional Cancer Centre, Toronto, Ontario, Canada. kathy.mah@tsrcc.on.ca
authors.forename: Katherine
authors.initials: K
authors.lastname: Mah
authors.forename: Curtis B
authors.initials: CB
authors.lastname: Caldwell
authors.forename: Yee C
authors.initials: YC
authors.lastname: Ung
authors.forename: Cyril E
authors.initials: CE
authors.lastname: Danjoux
authors.forename: Judith M
authors.initials: JM
authors.lastname: Balogh
authors.forename: S Nimu
authors.initials: SN
authors.lastname: Ganguli
authors.forename: Lisa E
authors.initials: LE
authors.lastname: Ehrlich
authors.forename: Romeo
authors.initials: R
authors.lastname: Tirona
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002289:Carcinoma, Non-Small-Cell Lung / Q000000981:diagnostic imaging* / Q000473:pathology; D005260:Female; D019788:Fluorodeoxyglucose F18; D006801:Humans; D008175:Lung Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology; D008207:Lymphatic Metastasis; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D019275:Radiopharmaceuticals; D011880:Radiotherapy Planning, Computer-Assisted; D014055:Tomography, Emission-Computed; D014057:Tomography, X-Ray Computed
chemical_list: D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18