Medullary thyroid carcinoma (MTC) is a rare tumor arising from C cells of the thyroid gland and belonging to the endocrine tumors. 18F-DOPA PET, based on tha capacity of endocrine tumor cells to take-up, decarboxylate and store amino-acids, such 3-4-dihydroxyphenylalanine(DOPA), is used for imaging endocrine tumors. The aim of the study was to evaluate the contribution of 18F-DOPA whole-body PET for the detection of recurrences in patients with proven recurrent MTC without evidence of recurrence or metastases on several imaging modalities.

In patients MTC and persistently elevated calcitonin levels, the challenge is finding the site of residual disease. Since the only satisfying treatment is surgery, the early detection and precise location is important. Tumor localization techniques usually performed, including ultrasonography of the neck and liver, chest and abdomen, bone scintigraphy, isotopic scanning and even PET with FDG are poorly sensitive. The use of 18F-DOPA may be more sensitive and specific engineering for localization metastatic disease. The study include 100 patient with persistent MTC demonstrated by elevated tumor markers (calcitonin and CEA) and no evidence of recurrence on morphological imaging procedures. 18F-DOPA whole-body PET is performed 30 minutes after IV injection of 4 MBq/kg of 18F-DOPA, the patient fasted for 6 hours prior the start of the examination.

All 18F-DOPA PET are evaluated independently by two experienced nuclear medicine physicians and any tracer accumulation exceeding the normal uptake tissue is rated as pathologic finding. The sensibility and efficiency of 18F-DOPA PET will be analysed and Malignant tissue confirmed by histology after surgery or biopsy or by follow-up for one year.

Inclusion criteria:

• Patients up to 18 years old with medullary thyroid cancer / carcinoma
• Patients with medullary thyroid cancer / carcinoma recurrence, which have a high calcitonin level / rate, more than 100pg/ml, associated - or not - to a high CEA (Carcinoembryonic Antibodies) level / rate, dated from less than 3 months
• Patients with a less than 3 months conventional imaging checkup (cervical ultrasonography, cervical-chest-abdomen tomography and / or magnetic resonance imaging, abdomen ultrasonography, osseous / bones radionuclide imaging), in which the tumor site not certainty located
• Informed Consent Form signed and dated by patients
• Patients which are "SECURITE SOCIALE" affiliated

Exclusion criteria:

• Pregnant or suckling women
• Women able to procreate, without efficient birth control
• Patients already included in another Nuclear Medicine or Imaging research protocol using ionizing radiations; the efficient dose accumulation will not exceed 20 mSv.