The role of PET in follow-up of patients treated for differentiated epithelial thyroid cancers

This article provides an update on the use of 2-[¹⁸F]-fluoro-2- deoxyglucose PET in the follow-up of patients treated for differentiated thyroid carcinoma (DTC). Although DTC recurrence is principally identified by a detectable basal or TSH-stimulated thyroglobulin level, PET helps to localize recurrent disease in patients with normal ¹³¹I total-body scans and other normal anatomic imaging studies. The sensitivity of PET for localization of recurrence ranges from 45% to 100% according to tumor burden and differentiation. Whether PET should be performed after TSH stimulation is unclear, but several studies have reported an increase in the number of lesions detected by uptake of 2-[¹⁸F]-fluoro-2-deoxyglucose in this setting. Dependent on a center's approach, PET can alter therapeutic management in 9-51% of cases. Furthermore, PET might have a prognostic impact on survival in patients with metastatic disease and aid clinicians in selecting patients who need closer follow-up or aggressive treatment. PET can, therefore, be used advantageously in the follow-up of patients with DTC and can localize disease in patients with elevated thyroglobulin levels, normal total-body scans, and normal findings on conventional imaging modalities. In patients in whom local treatment is planned, especially those with aggressive pathologic variants of thyroid cancer, PET can exclude distant metastases. In patients with metastatic disease, PET can help to identify patients needing closer follow-up.