Table 2. Thyroid Carcinomas in Children continued...
Initial treatment (defined as surgery plus one radioactive iodine ablation plus thyroid replacement) is effective in inducing remission for 70% of patients. Extensive disease at diagnosis and larger tumor size predict failure to remit. With additional treatment, 89% of patients achieve remission.
Periodic evaluations are required to determine whether there is metastatic disease involving the lungs. Lifelong follow-up is necessary. T4 and TSH levels should be evaluated periodically to determine whether replacement hormone is appropriately dosed. If thyroglobulin levels rise above postthyroidectomy baseline levels, recurrence of the disease is possible, and physical examination and imaging studies should be repeated. The use of various tyrosine kinase inhibitors or vascular endothelial growth factor receptor inhibitors has shown promising results in patients with metastatic or recurrent thyroid cancer in adults.[81,82,83,84]
Treatment of recurrent papillary and follicular thyroid carcinoma
Patients with differentiated thyroid cancer generally have an excellent survival with relatively few side effects.[80,85,86] Recurrence is common (35%-45%), however, and is seen more often in children younger than 10 years and in those with palpable cervical lymph nodes at diagnosis.[50,87,88] Even patients with a tumor that has spread to the lungs may expect to have no decrease in life span after appropriate treatment. Of note, the sodium-iodide symporter (a membrane-bound glycoprotein cotransporter), essential for uptake of iodide and thyroid hormone synthesis, is expressed in 35% to 45% of thyroid cancers in children and adolescents. Patients with expression of the sodium-iodide symporter have a lower risk of recurrence.
Recurrent papillary thyroid cancer is usually responsive to treatment with radioactive iodine ablation. Tyrosine kinase inhibitors such as sorafenib have shown to induce responses in up to 15% of adult patients with metastatic disease. Responses to sorafenib have also been documented in pediatric cases. Given the high incidence of BRAF mutations in older patients with papillary thyroid carcinoma, the use of selective RAF/MEK inhibitors is being investigated.[81,93,94]
Treatment of medullary thyroid carcinoma
Medullary thyroid carcinomas are commonly associated with the MEN2 syndrome (refer to the Multiple Endocrine Neoplasia (MEN) Syndromes and Carney Complex section of this summary for more information). They present with a more aggressive clinical course; 50% of the cases have hematogenous metastases at diagnosis. Patients with medullary carcinoma of the thyroid have a guarded prognosis, unless they have very small tumors (microcarcinoma, defined as <1.0 cm in diameter), which carry a good prognosis.