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., ¹³¹I, ¹²³I, ¹²⁴I) is an indispensable component of dynamic and theragnostic risk stratification of differentiated carcinoma (DTC) while [¹⁸F]F-fluorodeoxyglucose ([¹⁸F]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, [¹⁸F]F-dihydroxyphenylalanine (6-[¹⁸F]FDOPA) PET/CT and/or [¹⁸F]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.

Most patients with thyroid nodules and thyroid cancer (TC) referred for diagnostic work-up and treatment are not considered at higher risk of infection from SARS-CoV-2 compared to the general population. On the other hand, healthcare resources should be spared to the maximum extent possible during a pandemic. Indeed, while thyroid nodules are very common, only a small percentage are cancerous and, in turn, most thyroid cancers are indolent in nature. Accordingly, diagnostic work-up of thyroid nodules, thyroid surgery for either benign or malignant thyroid nodules and radioiodine treatment for differentiated thyroid cancers may be safely postponed during SARS-CoV-2 pandemic. Appropriate patient counselling, however, is mandatory and red flags should be carefully identified prompting immediate evaluation and treatment as appropriate. For these selected cases diagnostic work-up (e.g. ultrasound, scintigraphy, fine-needle aspiration), surgery and radioiodine therapy may proceed despite the threat of SARS-CoV-2 infection and COVID-19, after an individual risk-benefit analysis.

Differentiated thyroid cancer (DTC) is the most common subtype of thyroid cancer and has an excellent overall prognosis. However, metastatic DTC in certain cases may have a poor prognosis as it becomes radioiodine-refractory. Molecular imaging is essential for disease evaluation and further management. The most commonly used tracers are [¹⁸F]FDG and isotopes of radioiodine. Several other radiopharmaceuticals may be used as well, with different diagnostic performances. This review article aims to summarize radiopharmaceuticals used in patients with radioiodine-refractory DTC (RAI-R DTC), focusing on their different molecular pathways. Additionally, it will demonstrate possible applications of the theranostics approach to this subgroup of metastatic DTC.

Aim The objective of this study was to assess the impact of implementing FDG-PET imaging in treatment algorithms for differentiated thyroid cancer with suspected recurrence. Primary end points were overall, event-free and disease-specific survival. Secondary end points were therapies, disease control and the sensitivity and specificity of PET imaging. Methods 194 patients with DTC treated at our center from 1996 to 2014 following thyroidectomy and routine ¹³¹I ablation with no remaining ¹³¹I uptake in whole-body scans but persisting or rising thyroglobulin values were enrolled in this retrospective analysis. Of these, 149 (76.8 %) received an ¹⁸F-FDG scan (PET group) whereas the remaining 45 patients (23.2 %) did not (non-PET group). Survival, disease-specific characteristics at inclusion, disease control and therapies were compared. Results Patients of the PET group generally showed characteristics associated with higher disease activity from inclusion onwards. This did not translate to statistically significant differences in survival. If PET imaging was performed following inclusion, patients received significantly less radioiodine treatments during the first nine months after inclusion (63.1 % of the PET-group vs 82.2 % of the non-PET group). Simultaneously, patients tended to receive more surgeries following PET imaging (27.5 % PET-group vs 13.3 % non-PET group). No significant differences regarding disease control were observed. Conclusion The early use of FDG-PET imaging in cases of suspected recurrence or existence of dedifferentiated DTC can lead to changes in therapy management, specifically identifying patients unlikely to benefit from additional radioiodine therapy who would instead qualify for surgical therapy methods. Ziel Ziel dieser Studie war, die Auswirkung der FDG-PET(/CT)-Bildgebung bei der Behandlung des differenzierten Schilddrüsenkarzinoms bei Rezidivverdacht zu analysieren. Primäre Endpunkte waren Gesamt-, ereignisfreies und krankheitsspezifisches Überleben. Sekundäre Endpunkte waren biochemisches Therapieansprechen, Therapien und Sensitivität sowie Spezifität des PET(/CT). Methoden In die Studie wurden 194 Patienten eingeschlossen, die in unserer Klinik von 1996 bis 2014 im Anschluss an die Thyreoidektomie und ablative ¹³¹I-Radioiodtherapie behandelt wurden und trotz negativer Iodszintigraphien persistierende oder steigende Thyreoglobulinspiegel aufwiesen. Davon erhielten 149 (76,8 %) eine ¹⁸F-FDG-Bildgebung (PET-Gruppe), die anderen 45 Patienten (23,2 %) bildeten die non-PET-Gruppe. Die Gruppen wurden im Hinblick auf Überlebenszeiten, Patientencharakteristika bei Inklusion, biochemisches Therapieansprechen und Therapien verglichen. Ergebnisse Patienten der PET-Gruppe wiesen generell ab Inklusion mehr Merkmale auf, die mit einer höheren Krankheitslast einhergehen. Dies resultierte nicht in statistisch signifikanten Unterschieden der Überlebenszeiten. Wurde eine PET(/CT)-Bildgebung durchgeführt, erhielten die Patienten signifikant weniger Radioiodtherapien in den ersten 9 Monaten nach Inklusion (63,1 % PET; 82,2 % non-PET). Gleichzeitig wurden tendenziell mehr Patienten operative Therapien zugeführt (27,5 % PET; 13,3 % non-PET). Das biochemische Therapieansprechen unterschied sich nicht signifikant. Zusammenfassung Der frühe Einsatz der PET(/CT)-Bildgebung bei Rezidivverdacht des differenzierten Schilddrüsenkarzinoms kann den Behandlungspfad verändern, indem diejenigen Patienten identifiziert werden, die von weiteren RIT wahrscheinlich nicht profitieren und stattdessen operativen Therapien zugeführt werden können.

Widely established compared to myocardial perfusion imaging, cardiac autonomous nervous system (CANS) assessment by radiopharmaceutical means is of potential use especially to arrhythmogenic diseases not correlated with anatomic or functional alterations revealed by classical imaging techniques. Molecular imaging of both pre- and postsynaptic functions of the autonomous nervous system is currently feasible, since single photon emission tomography (SPECT) and positron emission tomography (PET) have the ability to reveal the insights of molecular pathophysiology depicting both sympathetic and parasympathetic imbalance in discrete heart pathologies. This review provides not only a brief presentation of radiopharmaceuticals used for non-invasive CANS imaging in the case of ventricular arrhythmias, but also a current update on ventricular tachycardias, cardiomyopathies, Brugada and Long QT syndrome literature.