The Landscape of Pediatric Differentiated Thyroid Carcinoma and Predictors of Invasive Disease: A CATC Study

CONTEXT: Differentiated thyroid carcinoma (DTC) is rare in children, comprising 2-4% of pediatric cancers. Due to low case volumes at individual institutions, comprehensive data on patient and tumor characteristics and treatment outcomes are limited. The Child and Adolescent Thyroid Consortium (CATC) was established in 2019 to address this gap and to assess impact of changes in practice on outcomes. OBJECTIVE: This inaugural CATC study analyzes the landscape of pediatric DTC and predictors of invasive disease. DESIGN: International, multicenter retrospective analysis of children (< age 19) with DTC diagnosed from 2010-2019. SETTING: Five high-volume pediatric centers. RESULTS: The cohort included 715 children (78.3% female) diagnosed with DTC at median age 15.2 years (range: 3.2-18.9). There were 673 (94%) patients with papillary thyroid carcinoma (PTC) and 42 (6%) had follicular thyroid carcinoma (FTC). Among PTC patients, Stage 1(M0) disease was present in 562 individuals (83.5%; 222 N0, 161 N1a, and 179 N1b). Stage 2 (M1) disease was present in 111 (16.5%) children with PTC and 1/42 (2.4%) with FTC. Males and children <10 years exhibited more advanced T-, N-, and M-stages. Any extrathyroidal extension (ETE) correlated with increased nodal and pulmonary metastases. Oncogenic fusions, compared with BRAFV600E, were associated with more advanced N- and M-stages. Deintensification of therapy since 2015 was not associated with changes in disease outcomes. CONCLUSIONS: Invasive DTC is associated with age <10 years, male sex, tumors driven by oncogenic fusions and ETE. Despite less aggressive therapies in recent years, disease outcomes have not worsened. Recognition of these associations may guide care and prognostication.