Prognostic impact of ultrasonography features and ¹⁸F-fluorodeoxyglucose uptake in patients with papillary thyroid microcarcinoma

Objectives. To evaluate the prognostic impact of ultrasonography (US) features and 18F-fluorodeoxyglucose (18F-FDG) up­take in patients with papillary thyroid microcarcinoma (PTMC). Methods. This study included 74 patients with a single PTMC diagnosed pathologically. Patients underwent total thyroidec­tomy, or near-total thyroidectomy and staging thyroid US and positron emission tomography (PET) were performed prior to surgery. US features of thyroid nodules were reviewed retrospectively and the maximum standard uptake value (SUV) of nodules was semiquantitatively analyzed on 18F-FDG PET/computed tomography (CT). Patients were followed-up for recurrence, which was defined as PTC on cytology results, elevated serum thyroglobulin (Tg) or anti-Tg antibody levels, or uptake on whole-body scintigraphy. We used univariate and multivariate analyses to evaluate whether poor prognostic outcomes were associated with US features or SUV values derived from PET/CT of nod­ules. In addition, subjects were divided into 2 groups for subgroup analyses: one with nodules equal to or larger than 5 mm and one with nodules smaller than 5 mm. Results. Among the 74 patients, there was no recurrence. Thus we evaluated the correlation between SUV value and US features with poor prognostic factors of PTMC which included extrathyroid extension, central and lateral lymph node (LN) metastasis. However no clinicopathologic factors were associated with extrathyroid extension, central LN metastasis, or lateral LN metastasis. Conclusion. In patients with PTMC, US features and SUV values on FDG-PET were not related to extrathyroid extension or LN metastasis. However, future studies with a larger sample size and longer follow-up should be performed to verify the results of this study.