Dynamic Risk Stratification in the Follow-Up of Children and Adolescents with Differentiated Thyroid Cancer

Background: Risk stratification for persistent disease is an important step in pediatric differentiated thyroid cancer (DTC) management. The dynamic risk stratification (DRS) is a well validated system for adults, but not yet for children and adolescents. This study evaluated the DRS as well as other prognostic factors in pediatric DTC. Methods: Patients aged <= 18 years from four DTC tertiary teaching hospitals in Southern Brazil were included. Clinical characteristics were systematically retrieved, and all patients were classified according to the riskstratification system of the 2015 American Thyroid Association pediatric DTC guidelines (ATA risk) and according to DRS (excellent, indeterminate, biochemical, or structural incomplete responses). Disease status was evaluated after initial therapy and at last follow-up visit. Results: Sixty-six patients aged 14.5 +/- 3.0 years were studied of whom 54 (81.8%) were girls and 62 (93.9%) had papillary thyroid carcinomas. Tumor size was 2.3 cm (P25-75 1.6-3.5); 41 (63.1%) had cervical and 18 (27.7%) distant metastasis at diagnosis. All patients underwent total thyroidectomy, and 63 (95.5%) received radioiodine. Patients were classified according to DRS after initial therapy (n = 63) as follows: 21 (33%) excellent, 13 (21%) indeterminate, 6 (9%) biochemical, and 23 (37%) structural incomplete responses. Notably, after six years (P25-75 2.7-10.0), most patients remained in the same category. Interestingly, the cutoff analysis of stimulated postoperative thyroglobulin (sPOTg) through receiver operating characteristic curve showed that the value of 37.8 ng/mL showed 81% sensitivity and 100% specificity to predict an excellent response. Prognostic factors associated with persistent disease in the univariate analysis were TNM, ATA risk, DRS, and sPOTg. Conclusion: DRS after initial therapy and sPOTg are strong predictors of disease outcome and might be helpful for defining follow-up strategies in pediatric DTC.