title: Relationship between positive thyroglobulin doubling time and 18F-FDG PET/CT-positive, 131I-negative lesions.
abstract: OBJECTIVE
  In patients with differentiated thyroid carcinoma (DTC), metastases can either show iodine-131 (I) uptake on whole-body scintigraphy or F-2-fluoro-2-deoxy-D-glucose (F-FDG) uptake on combined PET and X-ray computed tomography (PET/CT), or a mix of both. The present study investigates the relationship between uptake patterns and prognosis in DTC patients, using thyroglobulin doubling time (TgDT) as a surrogate marker of prognosis.
  
  
  METHODS
  We retrospectively examined F-FDG PET/CT and I WBS in 65 DTC patients who were referred to our department of nuclear medicine for F-FDG PET/CT between May 2007 and June 2011.
  
  
  RESULTS
  Eight patients were excluded from analysis because of other diseases that caused intense F-FDG uptake or because of failure to show I WBS uptake. F-FDG uptake was seen in 30 out of 57 (53%) patients, of whom 14 showed some degree of I uptake. In these 30 positive scans, we identified a total of 181 F-FDG-positive lesions. Of these, 60 lesions (33%) showed concurrent I uptake on whole-body scintigraphy. Of the nine patients with a positive TgDT in the patient group eight had F-FDG-positive, I-negative lesions, indicating poorer prognosis for this group.
  
  
  CONCLUSIONS
  In this initial exploratory retrospective study there appears to be an association between a positive TgDT and F-FDG-positive, I-negative metastases, which should encourage further studies in order to establish whether F-FDG PET-CT is the preferred primary imaging modality in patients with a positive TgDT. Roughly two-thirds of patients with a negative TgDT will show at least some degree of I positivity, potentially enabling further I therapy.
authors.affiliation: Departments of aNuclear Medicine bMedical Statistics, RWTH University Hospital Aachen, Aachen, Germany cDepartment of Nuclear Medicine, Maastricht University Medical Center, Maastricht, The Netherlands.
authors.forename: Anita
authors.initials: A
authors.lastname: Kelders
authors.forename: Lieven N
authors.initials: LN
authors.lastname: Kennes
authors.forename: Thomas
authors.initials: T
authors.lastname: Krohn
authors.forename: Florian F
authors.initials: FF
authors.lastname: Behrendt
authors.forename: Felix M
authors.initials: FM
authors.lastname: Mottaghy
authors.forename: Frederik A
authors.initials: FA
authors.lastname: Verburg
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D019788:Fluorodeoxyglucose F18; D006801:Humans; D007457:Iodine Radioisotopes; D008297:Male; D008875:Middle Aged; D064847:Multimodal Imaging; D049268:Positron-Emission Tomography; D011379:Prognosis; D012189:Retrospective Studies; D013954:Thyroglobulin / Q000378:metabolism*; D013964:Thyroid Neoplasms / Q000175:diagnosis* / Q000000981:diagnostic imaging / Q000378:metabolism*; D013997:Time Factors; D014057:Tomography, X-Ray Computed; D051598:Whole Body Imaging; D055815:Young Adult
chemical_list: D007457:Iodine Radioisotopes; D019788:Fluorodeoxyglucose F18; D013954:Thyroglobulin