Age, ATA risk group and response to therapy are prognostic factors in children with differentiated thyroid cancer.

BACKGROUND Against the background of increasing incidence, pediatric differentiated thyroid carcinoma (DTC) frequently presents with advanced disease and high recurrence rates while prognosis remains excellent. We investigated the use of a pediatric classification and an adult response to therapy risk stratification for pediatric DTC patients and their implications for adaptation of treatment and follow-up. METHODS Data from patients aged <18 years with a diagnosis of primary DTC, registered with the GPOH-MET registry since 1995 were analyzed. For risk prediction, patients were retrospectively assigned to the American Thyroid Association (ATA) risk groups and evaluated for response to therapy. RESULTS By October 2019, 354 patients with DTC had been reported (median age at diagnosis 13.7 years, range 3.6-17.9) with lymph node and distant metastases in 74.3% and 24.5%. Mean follow-up was 4.1 years (range 0-20.6). 10-years overall and event-free survival (EFS) rates were 98.9% and 78.1%. EFS was impaired for patients with lymph node and distant metastases (p<0.001), positive postoperative thyroglobulin (p=0.006), incomplete resection (p=0.002), sequential surgeries to achieve total thyroidectomy (p=0.042), invasion of capsule (p<0.001) and lymph vessels (p=0.005), infiltration of surrounding soft tissues (p<0.001), tumor multifocality (p<0.001), ATA intermediate- and high-risk group (p<0.001), and age <10 years (p<0.001). Multivariate analysis revealed age <10 years at diagnosis, ATA high-risk level, and poor response to therapy as significant negative prognostic factors for EFS. CONCLUSIONS Age, ATA risk group, and response to therapy emerged as significant prognostic factors for EFS in pediatric patients with DTC, requiring risk-adapted individualized therapy and follow-up.