18F-FDG PET/CT may exclude malignancy in sonographically suspicious and scintigraphically hypofunctional thyroid nodules and reduce unnecessary thyroid surgeries.

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18F-FDG PET/CT may exclude malignancy in sonographically suspicious and scintigraphically hypofunctional thyroid nodules and reduce unnecessary thyroid surgeries.

Thyroid. 2017 Aug 10;:

Authors: Ruhlmann M, Ruhlmann J, Görges R, Herrmann K, Antoch G, Keller HW, Ruhlmann V

Abstract
BACKGROUND: The aim of this study was to evaluate whether [18F]-fluorodeoxyglucose positron emission tomography/computed tomography (FDG-PET/CT) is useful in the further characterization of sonographically suspicious and scintigraphically hypofunctional thyroid nodules.
METHODS: 65 patients with a sonographically suspicious thyroid nodules that were hypofunctional on 99m-Tc-pertechnetate scintigraphy (diameter > 1 cm) were retrospectively analyzed. All patients underwent evaluation with FDG-PET/CT. Thyroid nodules were sonographically categorized by TIRADS criteria. FDG uptake in the thyroid nodules was visually compared with the remainder of the thyroid tissue and categorized as pathological or non-pathological. In cases of pathologically increased uptake, maximum standardized uptake value (SUVmax) of the suspicious nodule and the perinodular thyroid tissue were determined. Depending on the results of the FDG-PET/CT, patients underwent thyroid surgery (pathological FDG uptake) or follow-up examinations (non-pathological FDG uptake). The endpoints for comparison with the FDG uptake were either histological results or sonographic follow-up examinations of at least 5 years.
RESULTS: In 18/65 (28%) patients PET/CT showed visually pathological FDG uptake in the suspicious thyroid nodules (SUVmax 7.1 ± 4.6). 3/18 (17%) of these nodules were sonographically categorized as TIRADS 4a, 11/18 (61%) nodules as TIRADS 4b, 3/18 (17%) nodules as TIRADS 4c and 1/18 (6%) nodule as TIRADS 5. The other nodules without pathological FDG uptake were categorized as TIRADS 4a in 24/47 (51%) patients, as TIRADS 4b in 18/47 (38%), and as TIRADS 4c in 5/47 (11%) patients. 23 patients (18 FDG positive, 5 FDG negative) underwent surgery. The other patients underwent follow-up examinations with stability on observation over at least 5 years as a surrogate endpoint. Taking into consideration, that FDG-PET/CT was rated as true negative in 42/47 patients with stability on sonographic follow-up, sensitivity, specificity, PPV and NPV of FDG-PET/CT in detecting malignancy in the suspicious thyroid nodules was 100%, 87%, 61% and 100%, respectively.
CONCLUSION: FDG-PET/CT allows stratification of patients with sonographically suspicious and scintigraphically hypofunctional thyroid nodules with a PPV of 61% and NPV of 100%. The absence of visually pathological FDG uptake in suspicious thyroid nodules may be useful for avoiding unnecessary thyroid surgery.

PMID: 28793848 [PubMed - as supplied by publisher]

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