Trends in Clinicopathologic Characteristics of Pediatric Differentiated Thyroid Carcinoma: A Single-Center Experience from 1995 to 2022

Background: The incidence of pediatric differentiated thyroid carcinoma (DTC) has increased, but temporal trends in its clinicopathologic features remain unclear. We evaluated changes in the clinicopathologic features and treatment trends of pediatric DTC from 1995 to 2022. Methods: This study included 168 pediatric DTC patients treated at Samsung Medical Center, Korea. The patients were grouped according to the year of initial surgery: Period 1 (1995-2005), Period 2 (2006-2010), Period 3 (2011-2015), and Period 4 (2016-2022). The primary outcome was recurrence-free interval. Results: Age at diagnosis, primary tumor size, Tumor-Node-Metastasis (TNM) stage, and route of detection did not differ across periods. However, the distribution of American Thyroid Association (ATA) risk categories shifted toward lower-risk disease (P for trend=0.041), and the incidence of diffuse sclerosing variant papillary thyroid carcinoma (DSV-PTC) increased (P for trend=0.003). Additionally, the extent of surgery decreased (P for trend <0.001), and radioactive iodine (RAI) therapy was administered less frequently over time (P for trend <0.001). Among patients who received RAI therapy, cumulative dose within 2 years after surgery significantly decreased (P for trend=0.005), particularly in the ATA low- and intermediate-risk groups. DSV-PTC, and the ATA highrisk group were significant predictors of disease recurrence. However, the diagnostic era was not significantly associated with disease recurrence (log-rank P=0.468). Conclusion: In this single-center cohort study, age at diagnosis, primary tumor size, TNM stage, and route of detection remained consistent over time; however, the proportion of DSV-PTC increased. Treatment strategies shifted toward more conservative approaches, especially in low- and intermediate-risk groups.