The usefulness of serum thyroglobulin in the follow-up of differentiated thyroid carcinoma in children.

Serum thyroglobulin has been measured serially in ten children aged 5-17 years presenting with differentiated thyroid carcinoma. At presentation 4 had intra-thyroidal disease, 3 had lymph node metastases, and 3 had lung metastases. During follow-up for a median of 37.0 months (range 21-108) 3 patients have been disease-free, 4 have had a local relapse, and 3 have had persistent disease. Seventy-seven separate serum thyroglobulin measurements have been performed; 36 on and 41 off thyroid replacement therapy. A level of thyroglobulin of less than 5 ng/ml was taken as indicative of absence of disease, and compared against combined clinical examination and 131I scanning. Overall sensitivity of thyroglobulin measurement was 36/37 (97%), and although specificity was 30/40 (75%), this rose to 30/32 (94%) if raised thyroglobulin levels noted within 3 months of 131I therapy in otherwise asymptomatic patients (n = 4) or in subjects with intact thyroid tissue (n = 4) were excluded. Concordance with clinical status was 30/31 (97%) in measurements taken on, and 31/32 (94%) in those taken off, thyroid replacement. These data indicate that thyroglobulin measurement is a sensitive and specific means of detecting residual, recurrent, and metastatic thyroid carcinoma in children.