Abstract: Background and purpose: In recent years, the incidence of the thyroid carcinoma in children and adolescents has increased significantly. This study aimed to explore the clinicopathological risk factors for children and adolescents with distant metastasis of differentiated thyroid carcinoma (caDTC). Methods: Totally, 69 patients with DTC (<21 years) treated in Department of Nuclear Medicine, Peking Union Medical College Hospital from Feb. 2007 to Oct. 2018 were retrospectively analyzed in this study. Patients were divided into two groups as per the presence of distant metastases or not: group A (n=40) and group B (n=29). For comparison between the two groups, t-test was used to compare the ages, χ² test was used to compare the gender, extrathyroidal invasion, multifocality and BRAF^V600E, while the Mann-Whitney U test was used to compare the tumor size, T stage, N stage, preablation-stimulated thyroglobulin (ps-Tg) and thyroglobulin antibody (TgAb). The receiver operating characteristic (ROC) curve was analyzed to evaluate the predictive value of ps-Tg for distant metastasis. Multivariate logistic regression analysis was used to identify predictors of distant metastasis. Results: Group A showed younger age at diagnosis, more likelihood of multifocality, higher pathological stage and higher ps-Tg level, while the two groups did not differ in gender, extrathyroidal invasion, tumor size and TgAb. Area under the ROC curve was 0.900. The cut-off point of ps-Tg was 102.35 ng/mL, with a sensitivity of 70.0%, specificity of 100%, and negative predictive value of 70.7%. In further multivariate logistic regression analysis, age and ps-Tg were confirmed to be predictors of distant metastasis. Conclusion: Young age, high ps-Tg level, and advanced local invasion characteristics such as multifocality and higher tumor stage are associated with the distant metastasis of caDTC. With a cut-off of 102.35 ng/mL, ps-Tg holds the predictive value in identifying distant metastasis of caDTC.

Key words: Differentiated thyroid carcinoma, Distant metastasis, Children, Adolescents