What is the role of florine-18 fluorodeoxyglucose/positron emission tomography/computed tomography imaging in well-differentiated thyroid cancers with negative iodine-131 scan high thyroglobulin and normal anti-thyroglobulin levels

J Cancer Res Ther. Apr-Jun 2016;12(2):1010-7. doi: 10.4103/0973-1482.176412.


Purpose: This retrospective study aims to assess the cut-off value of thyroglobulin (Tg) levels in nux or metastatic well-differentiated thyroid cancers (DTCs) with normal anti-Tg levels using with fluorodeoxyglucose/positron emission tomography/computed tomography (FDG PET/CT).

Materials and methods: We reviewed FDG PET/CT images of 104 patients with well DTC (28 men, 76 women) whose: Iodine-131 (131 I) whole-body scanning was negative but had elevated Tg with normal anti-Tg levels.

Results: The overall sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and accuracy of florine-18-FDG PET/CT findings were found to be 95.92%, 87.27%, 87.04%, 96.00%, and 91.35%, respectively. The best Tg cut-off value was found to be 10.4 ng/ml. In the Tg level <10.4 ng/ml group, the sensitivity, specificity, PPV, NPV, and accuracy of FDG PET/CT were found to be 94.1%, 91.30%, 88.8%, 95.4%, and 92.5%, respectively. In the other group, which Tg level ≥10.4 ng/ml, sensitivity, specificity, PPV, NPV, and accuracy of FDG PET/CT exams were found to be 96.8%, 84.3%, 86.1%, 96.4%, and 90.6%, respectively.

Conclusion: FDG PET/CT imaging is a valuable imaging method in the evaluation of patients with elevated serum Tg levels and normal anti-Tg levels. Furthermore, it has potential utility in the dedifferentiation of active foci that are present, and in assessing optimal decision making during follow-up.

MeSH terms

  • Adolescent
  • Adult
  • Aged
  • Autoantibodies / blood*
  • Biomarkers
  • Child
  • Female
  • Fluorodeoxyglucose F18*
  • Humans
  • Iodine Radioisotopes*
  • Male
  • Middle Aged
  • Positron Emission Tomography Computed Tomography* / methods
  • Reproducibility of Results
  • Retrospective Studies
  • Sensitivity and Specificity
  • Thyroglobulin / blood*
  • Thyroid Neoplasms / blood*
  • Thyroid Neoplasms / diagnosis*
  • Thyroid Neoplasms / therapy
  • Young Adult


  • Autoantibodies
  • Biomarkers
  • Iodine Radioisotopes
  • anti-thyroglobulin
  • Fluorodeoxyglucose F18
  • Thyroglobulin