Is (18)F-fluorodeoxyglucose-PET/CT useful for the presurgical characterization of thyroid nodules with indeterminate fine needle aspiration cytology?

Thyroid. 2012 Feb;22(2):165-72. doi: 10.1089/thy.2011.0255. Epub 2012 Jan 18.

Abstract

Background: Thyroid nodules found incidentally on (18)F-fluorodeoxyglucose-positron emission tomography (FDG-PET) have been shown to be malignant in 30%-50% of cases. The American Thyroid Association recommends performing fine needle aspiration cytology (FNAC) for thyroid nodules showing FDG uptake. On the other hand, the role of FDG-PET in characterizing thyroid nodules with indeterminate cytology before surgery is not clear. The goal of this study was to evaluate the role of FDG-PET/computed tomography (CT) in predicting malignancy of thyroid nodules with indeterminate FNAC and to correlate FDG uptake with pathological and ultrasonographic (US) features.

Methods: Between November 2006 and October 2009, 55 patients (42 women, mean age: 50 years) planned for surgery for 56 thyroid nodules with indeterminate FNAC were prospectively included and considered for analysis. All patients underwent presurgical FDG-PET/CT (Siemens Biograph, mean FDG injected activity: 165 MBq) and neck US. Pathology of the corresponding surgical specimen was the gold standard for statistical analysis.

Results: At pathology 34 nodules were benign, 10 were malignant (7 papillary and 3 follicular carcinomas), and 12 were tumors of uncertain malignant potential (TUMP). The median size of the thyroid nodules was 21 mm (range: 10-57). Sensitivity, specificity, positive (PPV), and negative predictive (NPV) values of FDG-PET in detecting cancer/TUMP were 77%, 62%, 57%, and 81%, respectively. In multivariate analysis, cellular atypia was the only factor predictive of FDG uptake (p<0.001). Hurthle cells and poorly differentiated components were independent predictive factors of high (≥5) SUV Max (p=0.02 and p=0.02). Sensitivity, specificity, PPV, and NPV of US in detecting cancer/TUMP were 82%, 47%, 50%, and 80%, respectively. In multivariate analysis, hypervascularization was correlated with malignancy/TUMP (p=0.007) and cystic features were correlated with benignity (p=0.03).

Conclusion: Adding FDG-PET findings to neck US provided no diagnostic benefit. The sensitivity and specificity of FDG-PET in the presurgical evaluation of indeterminate thyroid nodules are too low to recommend FDG-PET routinely.

MeSH terms

  • Adenocarcinoma, Follicular / diagnostic imaging*
  • Adult
  • Aged
  • Biopsy, Fine-Needle
  • Carcinoma, Papillary / diagnostic imaging*
  • Female
  • Fluorodeoxyglucose F18*
  • Humans
  • Male
  • Middle Aged
  • Multimodal Imaging / methods*
  • Positron-Emission Tomography*
  • Sensitivity and Specificity
  • Thyroid Neoplasms / diagnostic imaging*
  • Thyroid Nodule / diagnostic imaging*
  • Tomography, X-Ray Computed*
  • Ultrasonography

Substances

  • Fluorodeoxyglucose F18