The role of ultrasound in the follow-up of children with differentiated thyroid cancer

Thyroid cancer is the most common endocrine malignancy with relatively good prognosis in children. However, unlike adults, children usually present with more advanced disease and have a higher local recurrence and distant metastases. Thus surveillance for recurrence is a major goal of long-term follow-up. This retrospective study evaluates the diagnostic value of ultrasound (US) imaging in the post-therapy surveillance of children with differentiated thyroid cancer. We reviewed the charts of 54 children (40 girls; mean age 14.3 +/- 3.6 years) with differentiated thyroid cancer treated with total or near-total thyroidectomy. Forty children (29 girls and 11 boys) who had routine follow-up US examinations (112 studies) were included for the evaluation of US accuracy in the follow-up of pediatric differentiated thyroid cancer. Histopathology, stimulated thyroglobulin determination, post-therapy whole-body iodine scan and clinical follow-up were used as the standards of reference. Mean period of follow-up was 34 months. The frequency of recurrence was 42% (17/40). Seventeen percent of the children had lung metastases either at presentation or on follow-up. In all cases of lung metastases, stimulated thyroglobulin level was greater than 10 ng/ml. The sensitivity was 85.7%, specificity 89.4%, negative predictive value 94.4% and positive predictive value 75% for US in detecting loco-regional recurrence in follow-up studies of pediatric differentiated thyroid cancer. In 17.3% (18/104) of studies, the results of stimulated thyroglobulin and US were discordant. US showed very good sensitivity and specificity and a high negative predictive value for evaluation of loco-regional involvement in follow-up of pediatric differentiated thyroid cancer. Diagnostic whole-body iodine scan is indicated when serum anti-thyroglobulin Ab is high, or in cases of discordant findings between US and stimulated thyroglobulin levels, or when stimulated thyroglobulin levels are > 10 ng/ml (to evaluate for lung metastasis).