Approach to the thyroid cancer patient with extracervical metastases

Patients with distant, or extracervical, metastases from differentiated thyroid cancer require multimodality diagnostic, therapeutic, and monitoring approaches. Whereas cure is the initial goal, especially in those with small, radioiodine-avid pulmonary metastases, improved survival and management of symptoms become the primary objective in many patients with persistent disease, especially those with bone metastases. Levothyroxine therapy with suppression of serum TSH is a primary therapy in all patients with advanced differentiated thyroid cancer, and this therapy has been shown to improve overall survival and slow disease progression. Radioiodine is also an important systemic therapy for those patients with radioiodine-avid disease who respond to this targeted therapy. In this review, we compare standard fixed-dose radioiodine therapy vs. the dosimetric approach. Directed therapy such as external beam radiotherapy, surgery, and embolization is generally considered for large or painful lesions. Careful collaborations with multiple specialties through tumor boards or other mechanisms help to optimize complex management decisions in these patients with advanced thyroid cancer. Multimodality monitoring focused on the organ of interest such as pulmonary [computed tomography (CT)], bone (magnetic resonance imaging, CT, bone scan), and brain (CT, magnetic resonance imaging) metastases as well as general metastatic surveillance (bone scan, (18)F-fluorodeoxyglucose-positron emission tomography) aid decision making about careful monitoring vs. directed or systemic therapy. (18)F-fluorodeoxyglucose-positron emission tomography imaging has an additional role in patient prognosis and guiding directed therapy for fluorodeoxyglucose-avid lesions. Patients with asymptomatic, stable, radioiodine-resistant metastases may be carefully monitored for disease progression. Patients with symptomatic disease should receive directed therapy with the goal of symptom relief. Patients with progressive metastatic disease should be considered for clinical trials or targeted systemic therapy (sorafenib or sunitinib), although these agents are not Food and Drug Administration (FDA) approved for patients with thyroid cancer. The goals of therapy for patients with extracervical metastases should be to improve survival, relieve symptoms, and decrease the morbidity of disease progression and limit the morbidity associated with therapy.