title: Can (18)F-FDG-PET/CT be generally recommended in patients with differentiated thyroid carcinoma and elevated thyroglobulin levels but negative I-131 whole body scan?
abstract: BACKGROUND
  Exact localization of recurrent iodine-negative thyroid cancer is mandatory, since surgery is the only curative therapy option in patients with iodine-negative tumor tissue. The aim of this study was to evaluate the impact of (18)F-FDG-PET/CT as a routine diagnostic tool on clinical management in patients with suspected thyroid cancer recurrence and elevated serum thyroglobulin (Tg) but negative radioiodine whole body scan.
  
  
  METHODS
  After total thyroidectomy followed by radioiodine ablation, 30 consecutive patients with differentiated thyroid cancer, elevated serum thyroglobulin levels and negative whole body radioiodine scan underwent (18)F-FDG-PET/CT. Results were verified by histology, ultrasound, or clinical follow-up. Diagnostic accuracy was determined for the whole study population and for subgroups with serum thyroglobulin below and above 10 ng/ml, respectively. Impact of PET/CT on clinical management was assessed.
  
  
  RESULTS
  PET/CT identified FDG accumulating lesions in 19 of 30 patients. 17 were true-positive and 2 false-positive. In the true-positive group, 11 of the 17 patients had loco-regional disease, 3 had distant metastases only and 3 patients had both loco-regional and distant metastatic involvement. (18)F-FDG-PET/CT was true-negative in 3 patients and false-negative in 8 patients. Overall sensitivity, specificity and accuracy were 68.0, 60.0, and 66.7%, respectively. In the subgroup of patients with serum thyroglobulin above 10 ng/ml (n = 21) the sensitivity, specificity and accuracy were substantially higher with 70.0, 100.0, and 71.4%, respectively. Clinical management was changed for 17 (57%) of 30 patients, guiding to a curative surgical intervention in 9 patients (30%).
  
  
  CONCLUSIONS
  (18)F-FDG-PET/CT enables detection and precise localization of loco-regional recurrence and distant metastases of differentiated thyroid cancer in patients with elevated serum thyroglobulin but negative radioiodine with significant impact on patient management and can therefore be recommended as a routine diagnostic tool.
authors: Department of Diagnostic and Interventional Radiology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany. p.bannas@uke.de
authors: Peter
authors: P
authors: Bannas
authors: Thorsten
authors: T
authors: Derlin
authors: Michael
authors: M
authors: Groth
authors: Ivayla
authors: I
authors: Apostolova
authors: Gerhard
authors: G
authors: Adam
authors: Janos
authors: J
authors: Mester
authors: Susanne
authors: S
authors: Klutmann
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002648:Child; D005260:Female; D019788:Fluorodeoxyglucose F18; D006801:Humans; D007457:Iodine Radioisotopes; D008297:Male; D008875:Middle Aged; D064847:Multimodal Imaging; D009333:Neck / Q000000981:diagnostic imaging; D049268:Positron-Emission Tomography; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D013954:Thyroglobulin / Q000097:blood*; D013964:Thyroid Neoplasms / Q000097:blood* / Q000000981:diagnostic imaging* / Q000473:pathology / Q000628:therapy; D014057:Tomography, X-Ray Computed; D014463:Ultrasonography; D051598:Whole Body Imaging; D055815:Young Adult
chemical_list: D007457:Iodine Radioisotopes; D019788:Fluorodeoxyglucose F18; D013954:Thyroglobulin