Differentiated Thyroid Carcinoma with Elevated Thyroglobulin and Negative Radioiodine Whole-Body Scan Metastases

Abstract

Serum thyroglobulin Tg and Tg antibody Tg"b levels, together with neck ultrasonography and I whole-body scintigraphy W"S , are diagnostic tools for postoperative follow-up of patients with differentiated thyroid carcinoma DTC . Generally, good correlation is seen between Tg and W"S in follow-up studies for DTC after thyroid remnant ablation. Undetectable serum Tg with negative W"S results suggests complete remission, whereas detectable, or elevated, serum Tg is associated with radioiodine uptake in local or distant metastases. Patients with thyroid cancer cells lacking radioiodine uptake despite an elevated serum Tg level have been referred to as W"S-negative, Tg-positive patients, who represent % of cases. F-FDG PET FDG-PET scanning should be considered in high-risk DTC patients with negative W"S and positive Tg. The preferred therapeutic hierarchy for Tg-positive and W"Snegative metastases is surgical excision of loco-regional disease, I therapy for radioiodine-responsive disease, external beam radiation, TSH suppression, and systemic therapy with kinase inhibitors. If FDG-PET diagnostic results are negative, one course of I treatment may be considered in high-risk patients and individualized. No further I therapy is indicated for patients with a negative post-therapy W"S.