Positron Emission Tomography Imaging in Medullary Thyroid Carcinoma: Time for Reappraisal?

Medullary thyroid carcinomas (MTC) are rare neoplasms derived from calcitonin-secreting cells of the thyroid. They can occur sporadically or as part of the multiple endocrine neoplasia type 2 syndromes. Overall, successful management of MTC patients heavily relies on the patient's conditions, tumor stage, genetic background, and the medical team's experience. Over the past 10 years, many consensus or near consensus of expert panels have been published for the treatment and follow-up of MTC (e.g., American Thyroid Association [ATA] 2009, ATA 2015, European Society of Medical Oncology [ESMO] 2019, European Association of Nuclear Medicine [EANM] 2020). The recent 2020 EANM guidelines recommend in particular to carry out 18F-FDOPA (6-18F-fluoro-L-3,4-dihydroxyphenylalanine) positron emission tomography/computed tomography scan (PET/CT scan) in MTC patients with persistent disease; however, this recommendation was not made in the 2015 ATA revised version. 18F-flurodeoxy glucose PET/CT scan is limited to aggressive forms, and PET imaging using 68Ga-somatostatin analogs appears suboptimal. This special article focuses on the clinical value of PET imaging in three common clinical scenarios (before initial thyroidectomy, before cervical reoperations for persistent/recurrent disease, and in the follow-up of metastatic cases).