Radioiodine Theranostics of Differentiated Thyroid Carcinoma

Abstract

AbstractCurrent management of patients with thyroid cancer requires a risk-adapted approach to treatment and multidisciplinary cooperation. Routine use of 131-I administration after total thyroidectomy is no longer recommended as this approach has been challenged by evidence that remnant ablation does not improve survival in low-risk patients. However, therapeutic 131-I administration in intermediate- and high-risk patients demonstrated significant benefits in improving overall survival. Radioiodine (131-I Na-I) is the classic agent used for the diagnosis and treatment of differentiated thyroid cancer (DTC) based on sodium–iodine symporter expression in normal and neoplastic thyroid tissues permitting the integration of diagnostic imaging and therapeutics using the same radionuclide (i.e., theranostics) targeting specific characteristics of tumor biology. Radioiodine theragnostics involves the acquisition of pre-ablation diagnostic scans (Dx Scans) to guide patient-individualized targeted 131-I therapy with goal of maximizing the benefits of the first therapeutic 131-I administration. Current imaging technology with hybrid SPECT/CT gamma camera systems has improved the capability of diagnostic radioiodine scintigraphy for identifying regional and distant metastatic disease and this imaging information can be used for 131-I treatment planning and delivery of activity-adjusted 131-I therapy for achieving intended treatment goals (e.g., remnant ablation, adjuvant treatment, and treatment of known disease). The goal of radioiodine theragnostics is to optimize the balance between 131-I therapeutic efficacy and potential side effects on non-target tissues. This chapter summarizes the new concepts and essential information at the core of multidisciplinary DTC management, which emphasizes individualization of 131I therapy according to the patient’s risk for tumor recurrence to maximize benefit and minimize morbidity.