A child with papillary thyroid cancer and metastatic pulmonary disease: Role of radioactive iodine therapy

Papillary thyroid carcinoma (PTC) is the most common pediatric endocrine malignancy. Cervical lymph node metastases occur in the vast majority of pediatric PTC, whereas pulmonary metastases occur in up to 25% of cases (depending on the series) and generally only with concomitant significant locoregional lymph node disease. Pulmonary metastases are typically micronodular and usually demonstrate excellent radioactive iodine (RAI) uptake, making them amenable to successful treatment with ¹³¹I. Although some children will demonstrate a complete response to RAI therapy, others will have persistent albeit stable disease following one or more courses of ¹³¹I. Clinical response to RAI may take several years to manifest, and more than one ¹³¹I treatment will need to be considered, especially in those children with high-volume pulmonary metastatic disease. Despite a higher risk of pulmonary metastases compared with adults, the risk of disease-specific mortality remains very low in children, and survival over decades is the norm. Therefore, the risks of repeated courses of ¹³¹I therapy (e.g., pulmonary fibrosis and secondary malignancies) need to be balanced against the risks of the disease itself, making the management of pulmonary metastatic disease in young children challenging. Contemporary approaches include postoperative risk stratification to identify those children at highest risk for distant metastatic disease and a more conservative approach to RAI treatment. Moreover, improved knowledge of the molecular drivers of pediatric PTC should help to improve risk stratification and provide a more individualized treatment approach in these patients.