Molecular Imaging and Theragnostics of Thyroid Cancers

According to the American Cancer Society, approximately 53,000 new cases of thyroid cancer were diagnosed and more than 2200 people died from the disease in 2020. New developments in molecular imaging are significantly improving thyroid cancer diagnostics and therapy. Continuous research in molecular imaging techniques additionally contributes to an understanding of a variety of diseases and enables more efficient care of thyroid cancer patients. Molecular imaging-based personalized therapy has been a fascinating concept for individualized therapeutic strategy, which is able to attain the highest efficacy and reduce adverse effects in certain patients. Theragnostics, which integrates diagnostic testing to detect molecular targets for particular therapeutic modalities, is one of the key technologies that contributes to the success of personalized medicine. This review details the inception of molecular imaging and theragnostic applications for thyroid cancer management. Molecular imaging plays an important role in the evaluation and management of different thyroid cancer histotypes. The existing risk stratification models can be refined, by incorporation of tumor-specific molecular markers that have theranostic power, to optimize patient-specific (individualized) treatment decisions. Molecular imaging with varying radioisotopes of iodine (i.e., I-131, I-123, I-124) is an indispensable component of dynamic and theragnostic risk stratification of differentiated carcinoma (DTC) while [F-18]F-fluorodeoxyglucose ([F-18]FDG) positron emission tomography/computed tomography (PET/CT) helps in addressing disease aggressiveness, detects distant metastases, and risk-stratifies patients with radioiodine-refractory DTC, poorly differentiated and anaplastic thyroid cancers. For medullary thyroid cancer (MTC), a neuroendocrine tumor derived from thyroid C-cells, [F-18]F-dihydroxyphenylalanine (6-[F-18]FDOPA) PET/CT and/or [F-18]FDG PET/CT can be used dependent on serum markers levels and kinetics. In addition to radioiodine therapy for DTC, some theragnostic approaches are promising for metastatic MTC as well. Moreover, new redifferentiation strategies are now available to restore uptake in radioiodine-refractory DTC while new theragnostic approaches showed promising preliminary results for advanced and aggressive forms of follicular-cell derived thyroid cancers (i.e., peptide receptor radiotherapy). In order to help clinicians put the role of molecular imaging into perspective, the appropriate role and emerging opportunities for molecular imaging and theragnostics in thyroid cancer are discussed in our present review.