title: Gallium-68 Dotatate PET/CT is superior to other imaging modalities in the detection of medullary carcinoma of the thyroid in the presence of high serum calcitonin.
abstract: OBJECTIVE
  Medullary carcinoma of the thyroid (MTC) is a rare neuroendocrine tumour (NET) that expresses somatostatin receptors on the cell membrane and secretes calcitonin. Surgery is the primary curative modality but is achieved only when the diagnosis is timely so there is a high rate of persistent and recurrent disease indicated by a rise in the serum calcitonin levels. Successful management of recurrent disease requires accurate localisation with cross sectional and functional imaging. The introduction of gallium-68-Dotatate ((68)Ga-Dotatate) peptides positron emission tomography/computerized tomography (PET/CT) has significantly improved the detection of NET and has been reported as a valuable adjunct in MTC localisation. We retrospectively reviewed our cases of MTC to correlate the detectability of (68)Ga-Dotatate in relation to calcitonin levels and assess suitability of inoperable patients for peptide receptor radionuclide therapy (PRRT).
  
  
  METHODS
  Seven patients (age range 31-66 years, M:F 3:4) with raised calcitonin (mean=7,143pg/mL) were referred for (68)Ga-Dotatate PET/CT scan for localisation of persisting recurrent MTC. Six patients were known to have MTC treated with thyroidectomy and one patient was presenting for the first time. All patients had multiple imaging including ultrasound (US), CT, magnetic resonance imaging (MRI), fluorine-18-fluorodeoxyglucose ((18)F-FDG) PET/CT and iodine-123-metaiodobenzylguanidine ((123)I-MIBG). Positive findings were defined as areas of increased uptake other than the organs of normal distribution and were correlated with results of biopsies, other imaging, long term monitoring of calcitonin and clinical follow up.
  
  
  RESULTS
  In 6/7 patients with very high serum calcitonin (range= 672-37,180, mean=8,320pg/mL) (68)Ga-Dotatate PET/CT confirmed the presence of active disease seen on other modalities or detected hitherto unsuspected lesions. In at least 3 cases, (68)Ga-Dotatate PET/CT showed many more lesions compared to other imaging combined. In 1/7 patient (68)Ga-Dotatate PET/CT was negative in line with a relatively low calcitonin level (80pg/mL) and negative disease on fine needle aspiration.
  
  
  CONCLUSIONS
  (68)Ga-Dotatate PET/CT is an effective tool for localising metastatic spread of MTC. It appears to be most effective in the presence of higher levels of serum calcitonin, probably in excess of 500pg/mL. The results of our small cohort had an impact on staging and management with the introduction of peptide receptor radionuclide therapy for inoperable disease.
authors: Department of Nuclear Medicine, Hammersmith Hospital, Imperial College NHS Trust, Du Cane Road, London W12 0HS, United Kingdom. Adil.al-nahhas@imperial.nhs.uk.
authors: Kathryn
authors: K
authors: Tran
authors: Sairah
authors: S
authors: Khan
authors: Mina
authors: M
authors: Taghizadehasl
authors: Fausto
authors: F
authors: Palazzo
authors: Andrea
authors: A
authors: Frilling
authors: Jeannie F
authors: JF
authors: Todd
authors: Adil
authors: A
authors: Al-Nahhas
mesh_terms: D000328:Adult; D000368:Aged; D002116:Calcitonin / Q000378:metabolism; D018276:Carcinoma, Medullary / Q000151:congenital* / Q000000981:diagnostic imaging*; D005260:Female; D005710:Gallium Radioisotopes; D006801:Humans; D007457:Iodine Radioisotopes; D008297:Male; D008875:Middle Aged; D064847:Multimodal Imaging / Q000379:methods*; D018813:Multiple Endocrine Neoplasia Type 2a / Q000000981:diagnostic imaging*; D009364:Neoplasm Recurrence, Local; D009942:Organometallic Compounds; D049268:Positron-Emission Tomography / Q000379:methods*; D011877:Radionuclide Imaging; D018000:Receptors, Peptide / Q000378:metabolism; D012189:Retrospective Studies; D013964:Thyroid Neoplasms / Q000000981:diagnostic imaging*; D014057:Tomography, X-Ray Computed / Q000379:methods*
chemical_list: D005710:Gallium Radioisotopes; D007457:Iodine Radioisotopes; D009942:Organometallic Compounds; D018000:Receptors, Peptide; D002116:Calcitonin; C513399:gallium Ga 68 dotatate