SUN-196 Long term outcomes of patients diagnosed with differentiated thyroid cancer in childhood and young adulthood

Abstract Disclosure: A. Valenciaga: None. S. Liyanarachchi: None. P.L. Brock: None. M.D. Ringel: None. Background: Rates of pediatric DTC in the United States have been increasing over the last few decades, largely in the adolescent group and in females more than males. The role of sex at birth and of puberty in development and overall prognosis of pediatric DTC has been a topic of interest. Children with DTC present with more advanced disease at diagnosis than their adult counterparts and have excellent prognosis. Studies on pediatric DTC have been limited by inconsistent age cut-off, short follow-up periods, or lack of clinical data. In the present study, we report long term outcomes in patients diagnosed with DTC at age 20 years old and younger. Methods: A retrospective study was conducted of patients diagnosed with DTC at age 20 years old or younger who were enrolled in an institutional biorepository. Their demographic and clinical information was extracted. Patients’ response to therapy was defined using the American Thyroid Association response criteria categories. Results: 155 patients were included, 143 (92.3%) with papillary thyroid cancer and 12 (7.7%) with follicular thyroid cancer. Median age at diagnosis was 17 years (9 to 20 years), with 31 patients (20%) diagnosed before age 15 (younger group) and 124 (80%) diagnosed between 15 and 20 years of age (older group). There were no differences in frequency of histological subtypes or sex distribution between the younger and older groups. Median duration of the entire cohort follow-up was 16 years (1 to 63 years). Most patients had stage I DTC (n=123, 79.4%) and N1 disease at diagnosis (n = 99, 63.9%). There was no association between birth sex and overall stage or between birth sex and N1 stage. Overall, the frequency of distant metastasis (Stage II disease) and larger tumors was inversely related to age at diagnosis (Overall stage p = 0.045, T-stage p = 0.001). At last follow-up, 52.3% of patients were in the excellent response category and disease specific mortality was 0%. There was no difference in response to therapy based on histologic subtype or birth sex; however, younger age at diagnosis was associated with worse response (p = 0.046). In the subset of patients with over 50 years of follow-up (n = 9), median of 36 years of stability was seen. After decades from diagnosis, progression occurred in 6 out of 9 (67%) patients. Conclusions: Patients diagnosed with PTC in childhood or as young adults in this cohort had an outstanding long-term survivorship. However, patients diagnosed at a younger age were more likely to have Stage II disease and more likely to have a poorer response to therapy. While prognosis was outstanding with long periods of stability, patients may experience disease progression later in life, suggesting long term follow-up is appropriate for those patients who do not achieve and excellent response. Presentation: Sunday, July 13, 2025