Prevalence and Significance of Thyroglobulin Antibodies in Pediatric Thyroid Cancer

Context: Circulating thyroglobulin antibodies (TgAb) can confound measurement of serum thyroglobulin and impair thyroid cancer surveillance. Few data exist on the significance of TgAb in pediatric thyroid cancer. Objective: To describe the prevalence, natural history, and clinical significance of TgAb in children with thyroid cancer. Design: Retrospective cohort study. Setting: Single academic pediatric center. Patients: Seventy-three consecutive children (<= 18 years) with nonmedullary thyroid cancer who had serum TgAb measured within 6 months after diagnosis. Main Outcome Measures: Prevalence and natural history of TgAb; association of TgAb status and resolution with patient and disease characteristics. Results: TgAb were detected in 41% of subjects (30 of 73) and were associated with lymph node metastasis (83% vs 53%, P = 0.01) but not distant metastasis. In patients with TgAb, resolution occurred in 44% (11 of 25) over a median follow-up of 3.8 years. Median time to clear TgAb was 10.7 months, and 10 of 11 patients who cleared (91%) did so within 2 years. Resolution of TgAb was associated with lower initial TgAb level (median 4.5 vs 76 normalized units, P = 0.003). TgAb positivity at diagnosis was not independently associated with persistent or recurrent disease (odds ratio 3.20, 95% confidence interval 0.95 to 10.80, P = 0.06). Conclusions: TgAb are common at diagnosis in children with thyroid cancer but resolve in nearly half of patients within 1 to 2 years. TgAb are associated with the presence of lymph node metastasis at diagnosis, but the long-term prognostic significance remains to be determined.