title: Repeatability of 18F-FDG PET/CT in Advanced Non-Small Cell Lung Cancer: Prospective Assessment in 2 Multicenter Trials.
abstract: PET/CT with the glucose analog (18)F-FDG has several potential applications for monitoring tumor response to therapy in patients with non-small cell lung cancer (NSCLC). A prerequisite for many of these applications is detailed knowledge of the repeatability of quantitative parameters derived from (18)F-FDG PET/CT studies.
  
  
  METHODS
  The repeatability of the (18)F-FDG signal was evaluated in 2 prospective multicenter trials. Patients with advanced NSCLC (tumor stage III-IV) underwent two (18)F-FDG PET/CT studies while not receiving therapy. Tumor (18)F-FDG uptake was quantified by measurement of the maximum standardized uptake value within a lesion (SUVmax) and the average SUV within a small volume of interest around the site of maximum uptake (SUVpeak). Analysis was performed for the lesion in the chest with the highest (18)F-FDG uptake and a size of at least 2 cm (target lesion) as well as for up to 6 additional lesions per patient. Repeatability was assessed by Bland-Altman plots and calculation of 95% repeatability coefficients (RCs) of the log-transformed SUV differences.
  
  
  RESULTS
  Test-retest repeatability was assessed in 74 patients (34 from the ACRIN 6678 trial and 40 from the Merck MK-0646-008 trial). SUVpeak was 11.57 ± 7.89 g/mL for the ACRIN trial and 6.89 ± 3.02 for the Merck trial. The lower and upper RCs were -28% (95% confidence interval [CI], -35% to -23%) and +39% (95% CI, 31% to 54%) in the ACRIN trial, indicating that a decrease of SUVpeak by more than 28% or an increase by more than 39% has a probability of less than 2.5%. The corresponding RCs from the Merck trial were -35% (95% CI, -42% to -29%) and +53% (95% CI, 41% to 72%). Repeatability was similar for SUVmax of the target lesion, averaged SUVmax, and averaged SUVpeak of up to 6 lesions per patient.
  
  
  CONCLUSIONS
  The variability of repeated measurements of tumor (18)F-FDG uptake in patients with NSCLC is somewhat larger than previously reported in smaller single-center studies but comparable to that of gastrointestinal malignancies in a previous multicenter trial. The variability of measurements supports the definitions of tumor response according to PET Response Criteria in Solid Tumors.
authors.affiliation: Memorial Sloan Kettering Cancer Center, New York, New York weberw@mskcc.org.
authors.forename: Wolfgang A
authors.initials: WA
authors.lastname: Weber
authors.affiliation: Department of Biostatistics and Center for Statistical Sciences, Brown University, Providence, Rhode Island.
authors.forename: Constantine A
authors.initials: CA
authors.lastname: Gatsonis
authors.affiliation: Merck & Co., Whitehouse Station, New Jersey.
authors.forename: P David
authors.initials: PD
authors.lastname: Mozley
authors.affiliation: Department of Biostatistics and Center for Statistical Sciences, Brown University, Providence, Rhode Island.
authors.forename: Lucy G
authors.initials: LG
authors.lastname: Hanna
authors.affiliation: Karmanos Cancer Institute, Wayne State University, Detroit, Michigan.
authors.forename: Anthony F
authors.initials: AF
authors.lastname: Shields
authors.affiliation: University of California-Los Angeles, Los Angeles, California.
authors.forename: Denise R
authors.initials: DR
authors.lastname: Aberle
authors.affiliation: Division of Oncology and the Siteman Cancer Center, Washington University School of Medicine, St. Louis, Missouri.
authors.forename: Ramaswamy
authors.initials: R
authors.lastname: Govindan
authors.affiliation: Department of Radiology, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania.
authors.forename: Drew A
authors.initials: DA
authors.lastname: Torigian
authors.affiliation: Department of Radiology, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania.
authors.forename: Joel S
authors.initials: JS
authors.lastname: Karp
authors.affiliation: Fox Chase Cancer Center, Philadelphia, Pennsylvania.
authors.forename: Jian Q Michael
authors.initials: JQ
authors.lastname: Yu
authors.affiliation: Russell H. Morgan Department of Radiology and Radiological Science and Sidney Kimmel Cancer Center, Johns Hopkins University, Baltimore, Maryland.
authors.forename: Rathan M
authors.initials: RM
authors.lastname: Subramaniam
authors.affiliation: Virginia Commonwealth University, Richmond, Virginia; and.
authors.forename: Robert A
authors.initials: RA
authors.lastname: Halvorsen
authors.forename: Barry A
authors.initials: BA
authors.lastname: Siegel
mesh_terms: D000368:Aged; D002289:Carcinoma, Non-Small-Cell Lung / Q000000981:diagnostic imaging*; D019788:Fluorodeoxyglucose F18; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008175:Lung Neoplasms / Q000000981:diagnostic imaging*; D008875:Middle Aged; D064847:Multimodal Imaging / Q000379:methods; D049268:Positron-Emission Tomography / Q000379:methods*; D011446:Prospective Studies; D019275:Radiopharmaceuticals; D015203:Reproducibility of Results; D014057:Tomography, X-Ray Computed / Q000379:methods*; D016896:Treatment Outcome
chemical_list: D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18
keywords: FDG PET/CT; quantification; repeatability; reproducibility