title: Diagnosis of metastases from postoperative differentiated thyroid cancer: comparison between FDG and FLT PET/CT studies.
abstract: OBJECTIVE
  To compare positron emission tomography (PET)/computed tomography (CT) studies performed with the glucose analog fluorine 18 ((18)F) fluorodeoxyglucose (FDG) and the cell proliferation tracer (18)F fluorothymidine (FLT) in the diagnosis of metastases from postoperative differentiated thyroid cancer.
  
  
  METHODS
  The institutional ethics review board approved this prospective study. From March 2010 to February 2012, 20 patients (mean age, 53 years; age range, 22-79 years) with postoperative differentiated thyroid cancer underwent both FDG and FLT PET/CT as a staging work-up before radioiodine therapy. In each patient, 28 anatomic areas were set and analyzed for lymph node and distant metastases. The McNemar exact or χ(2) test was used to examine differences in diagnostic indexes in the detection of lymph node and distant metastases between both tracer PET/CT studies.
  
  
  RESULTS
  There were 34 lymph node metastases and/or 73 distant metastases (70 metastases in lung and one each in bone, nasopharynx, and brain) in 13 patients. At patient-based analysis, the sensitivity, specificity, and accuracy were 92% (12 of 13 patients), 86% (six of seven patients), and 90% (18 of 20 patients), respectively, for FDG PET/CT and 69% (nine of 13 patients), 29% (two of seven patients), and 55% (11 of 20 patients) for FLT PET/CT. The accuracy of FDG PET/CT was significantly better than that of FLT PET/CT (P = .023). At lesion-based analysis, the sensitivity, specificity, and accuracy for diagnosing lymph node metastases were 85% (29 of 34 lesions), 99.6% (245 of 246 lesions), and 97.9% (274 of 280 lesions), respectively, for FDG PET/CT and 50% (17 of 34 lesions), 90.7% (223 of 246 lesions), and 85.7% (240 of 280 lesions) for FLT PET/CT. The sensitivity, specificity, and accuracy for diagnosing distant metastases were 45% (33 of 73 lesions), 100% (207 of 207 lesions), and 85.7% (240 of 280 lesions), respectively, for FDG PET/CT and 6.8% (five of 73 lesions), 100% (207 of 207 lesions), and 75.7% (212 of 280 lesions) for FLT PET/CT. The sensitivity (P = .002), specificity (P < .001), and accuracy (P < .001) of FDG PET/CT in the diagnosis of lymph node metastases were superior to those of FLT PET, as were the sensitivity (P < .001) and accuracy (P < .001) in the diagnosis of distant metastases.
  
  
  CONCLUSIONS
  FDG PET/CT is superior to FLT PET/CT in the diagnosis of postoperative differentiated thyroid cancer lymph node and distant metastases. Thus, FDG PET/CT is more suitable than FLT PET/CT for examining recurrence of postoperative differentiated thyroid cancer.
authors.affiliation: Department of Radiology, Kagoshima University, Graduate School of Medical and Dental Sciences, 8-35-1 Sakuragaoka, Kagoshima 890-8544, Japan. oyo.nakajo@dolphin.ocn.ne.jp
authors.forename: Masatoyo
authors.initials: M
authors.lastname: Nakajo
authors.forename: Masayuki
authors.initials: M
authors.lastname: Nakajo
authors.forename: Megumi
authors.initials: M
authors.lastname: Jinguji
authors.forename: Atsushi
authors.initials: A
authors.lastname: Tani
authors.forename: Yoriko
authors.initials: Y
authors.lastname: Kajiya
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Tanabe
authors.forename: Yoshihiko
authors.initials: Y
authors.lastname: Fukukura
authors.forename: Yoshiaki
authors.initials: Y
authors.lastname: Nakabeppu
authors.forename: Chihaya
authors.initials: C
authors.lastname: Koriyama
mesh_terms: D000328:Adult; D000368:Aged; D016009:Chi-Square Distribution; D015224:Dideoxynucleosides; D005260:Female; D019788:Fluorodeoxyglucose F18; D006801:Humans; D008207:Lymphatic Metastasis / Q000000981:diagnostic imaging*; D008297:Male; D008875:Middle Aged; D064847:Multimodal Imaging; D009364:Neoplasm Recurrence, Local / Q000000981:diagnostic imaging*; D049268:Positron-Emission Tomography; D011237:Predictive Value of Tests; D011446:Prospective Studies; D011857:Radiographic Image Interpretation, Computer-Assisted; D019275:Radiopharmaceuticals; D012680:Sensitivity and Specificity; D018709:Statistics, Nonparametric; D013964:Thyroid Neoplasms / Q000000981:diagnostic imaging / Q000473:pathology* / Q000601:surgery; D013965:Thyroidectomy; D014057:Tomography, X-Ray Computed; D051598:Whole Body Imaging
chemical_list: D015224:Dideoxynucleosides; D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18