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. 2012 May;34(5):626-31.
doi: 10.1002/hed.21791. Epub 2011 Aug 17.

Relationship between serum thyroglobulin and 18FDG-PET/CT in 131I-negative differentiated thyroid carcinomas

Luca Giovanella  1 , Luca Ceriani, Diego De Palma, Sergio Suriano, Massimo Castellani, Frederik A Verburg
Affiliations

Relationship between serum thyroglobulin and 18FDG-PET/CT in 131I-negative differentiated thyroid carcinomas

Luca Giovanella et al. Head Neck. 2012 May.

Abstract

Background: The purpose of this study was to assess the relationship between [(18) F]-fluorodeoxyglucose ((18) FDG)-positron emission tomography/CT ((18) FDG-PET/CT) and serum thyroglobulin (Tg) in patients with recurrent differentiated thyroid carcinoma (DTC).

Methods: Forty-two patients with recurrent DTC and negative Tg antibodies were included in the study. All patients underwent (131) I therapy due to an increasing serum Tg with a corresponding negative (131) I posttreatment whole body scan. The (18) FDG-PET/CT scans were then performed on all patients, serum Tg was measured concurrently, and respective results were compared.

Results: Sensitivity, specificity, negative predictive value (NPV), positive predictive value (PPV), and accuracy of the (18) FDG-PET/CT examination were 93%, 84%, 93%, 84%, and 90%, respectively. The sensitivity of (18) FDG-PET/CT significantly increased in patients with serum Tg levels ≥4.6 ng/mL (96%) in comparison with patients having lower levels (25%; p < .001). Nonetheless, 3 of 27 patients (11%) with a true-positive (18) FDG-PET/CT still had a Tg <4.6 ng/mL.

Conclusion: Although (18) FDG-PET/CT scans are more likely to be positive with pretest Tg levels ≥4.6 ng/mL, 11% of patients with DTC with a lower serum Tg level will still have a positive scan. Our findings are in contrast with the American Thyroid Association (ATA) guidelines, which only recommend to perform (18) FDG-PET/CT in patients with Tg levels >10 ng/mL.

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