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

Authors

  • Luca Giovanella MD,

    Corresponding author
    1. Department of Nuclear Medicine and Thyroid Diseases Centre, Oncology Institute of Southern Switzerland, Via Ospedale 12, CH-6500 Bellinzona, Switzerland
    • Department of Nuclear Medicine and Thyroid Diseases Centre, Oncology Institute of Southern Switzerland, Via Ospedale 12, CH-6500 Bellinzona, Switzerland
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  • Luca Ceriani MD,

    1. Department of Nuclear Medicine and Thyroid Diseases Centre, Oncology Institute of Southern Switzerland, Via Ospedale 12, CH-6500 Bellinzona, Switzerland
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  • Diego De Palma MD,

    1. Department of Nuclear Medicine, Ospedale di Circolo e Fondazione Macchi, I-21100 Varese, Italy
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  • Sergio Suriano MD,

    1. Department of Nuclear Medicine and Thyroid Diseases Centre, Oncology Institute of Southern Switzerland, Via Ospedale 12, CH-6500 Bellinzona, Switzerland
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  • Massimo Castellani MD,

    1. Department of Nuclear Medicine, Ospedale Maggiore-Policlinico, I-20122 Milano, Italy
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  • Frederik A. Verburg MD

    1. Department of Nuclear Medicine, University of Würzburg, D-97080 Würzburg, Germany
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Abstract

Background

The purpose of this study was to assess the relationship between [18F]-fluorodeoxyglucose (18FDG)-positron emission tomography/CT (18FDG-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 131I therapy due to an increasing serum Tg with a corresponding negative 131I posttreatment whole body scan. The 18FDG-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 18FDG-PET/CT examination were 93%, 84%, 93%, 84%, and 90%, respectively. The sensitivity of 18FDG-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 18FDG-PET/CT still had a Tg <4.6 ng/mL.

Conclusion

Although 18FDG-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 18FDG-PET/CT in patients with Tg levels >10 ng/mL. © 2011 Wiley Periodicals, Inc. Head Neck, 2012

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