Medullary thyroid carcinoma (MTC) develops at the expense of calcitonin cells and is often characterized by lymph node metastases (> 50% of cases) and sometimes visceral metastases (> 5%). Improvement of preoperative diagnosis is of major importance in CMT because the quality of the initial surgery determines the prognosis. In recent years, 18F-fluorodihydroxyphenylalanine (18F-FDOPA) PET / CT was considered the most sensitive functional imaging tool in the evaluation of persistent CMT. To date, 18F-FDOPA PET at initial diagnosis has been reported in a few clinical cases. Preliminary study, which included 9 CMT patients, 18F-FDOPA PET showed very promising results during the initial diagnosis, particularly in node staging.~The main objective is to demonstrate that 18F-FDOPA PET provides additional information compared to conventional imaging on the initial diagnosis of CMT patients. The secondary objectives are to describe the nature of the information provided by PET / CT imaging, the main factors influencing tracer uptake and the positivity of PET / CT, and the impact of the examination on the care of the patient.~This is a prospective, multicenter and open study.~Patients with TCM who have serum calcitonin> 150 pg / ml at initial diagnosis and have performed baseline imaging examinations (as recommended by the 2015 ATA) within the last 3 months will be included in the study . A PET at 18F-FDOPA will be performed according to a very powerful acquisition protocol. Image analysis will be performed blindly from the results of conventional imaging. All exams will be compared, in accordance with the gold standard. Therapeutic intentions will be collected before and after the PET imaging, as well as the actual management in place.~Number of patients expected: 62. Duration of the study: 29 months of inclusion and 7 months of follow-up.~About 60 to 70 patients with a CMT are operated annually in the centers involved. Nuclear physicians, endocrine surgeons, endocrinologists and anatomopathologists work together in institutional and interinstitutional team meetings (SFE-RENATEN). Some of the centers have already collaborated on the implementation of a large PHRC-INCa project recently published in the JCEM.
Medullary thyroid carcinoma (MTC) develops at the expense of calcitonin cells and is often characterized by lymph node metastases and sometimes visceral metastases. Improvement of preoperative diagnosis is of major importance in CMT because the quality of the initial surgery determines the prognosis. In recent years, 18F-fluorodihydroxyphenylalanine (18F-FDOPA) PET / CT was considered the most sensitive functional imaging tool in the evaluation of persistent CMT. To date, 18F-FDOPA PET at initial diagnosis has been reported in a few clinical cases.~The main objective is to demonstrate that 18F-FDOPA PET provides additional information compared to conventional imaging on the initial diagnosis of CMT patients.~The secondary objectives are to describe the nature of the information provided by PET / CT imaging, the main factors influencing tracer uptake and the positivity of PET / CT, and the impact of the examination on the care of the patient.~This is a prospective, multicenter and open study.~Patients with TCM who have serum calcitonin> 150 pg / ml at initial diagnosis and have performed baseline imaging examinations within the last 3 months will be included in the study . A PET at 18F-FDOPA will be performed according to a very powerful acquisition protocol. Image analysis will be performed blindly from the results of conventional imaging. All exams will be compared, in accordance with the gold standard. Therapeutic intentions will be collected before and after the PET imaging, as well as the actual management in place.