ORIGINAL ARTICLE Comparison of 68 Ga-DOTATATE and 18 F-fluorodeoxyglucose PET/CT in the detection of recurrent medullary thyroid carcinoma Brendon G. Conry & Nikolaos D. Papathanasiou & Vineet Prakash & Irfan Kayani & Martyn Caplin & Shahid Mahmood & Jamshed B. Bomanji Received: 13 May 2009 / Accepted: 9 June 2009 / Published online: 7 August 2009 # Springer-Verlag 2009 Abstract Purpose This was a retrospective study to detect and map the extent of disease in recurrent medullary thyroid carcinoma (MTC) using the novel PET somatostatin analogue 68 Ga-DOTATATE and conventional 18 F-FDG positron emission tomography/computed tomography (PET/CT). Methods Eighteen patients (13 men, 5 women, median age: 54 years) who had previously been operated on for MTC and presented with biochemical (raised calcitonin levels) and/or imaging evidence of recurrence underwent both 68 Ga-DOTATATE and 18 F-FDG PET/CT within a maxi- mum interval of 4 weeks (median interval of 1 week). 68 Ga-DOTATATE- and 18 F-FDG-avid lesions were recorded per patient as well as per region in six distinct regions: (1) thyroid bed—local recurrence, (2) cervical lymph nodes, (3) mediastinum, (4) lungs, (5) liver and (6) bones. The 68 Ga-DOTATATE and 18 F-FDG PET/CT find- ings were classified as positive or negative on visual interpretation. These findings were further characterised as concordant or discordant, depending on whether there was agreement or discrepancy in imaging with the two radio- tracers. A separate analysis of the unenhanced CT compo- nent of the examination was performed. Verification of the lesions was achieved by histopathological analysis, further imaging studies and clinical follow-up. Results 68 Ga-DOTATATE PET/CT imaging achieved dis- ease detection in 13 of 18 and 18 F-FDG PET/CT in 14 of 18 patients. These results corresponded to per-patient sensitiv- ities of 72.2% [95% confidence interval (CI): 46.4–89.3%] for 68 Ga-DOTATATE versus 77.8% (95% CI: 51.9–92.6%) for 18 F-FDG (non-significant difference). 18 F-FDG revealed a total of 28 metastatic MTC regions and 68 Ga-DOTATATE 23 regions. In ten patients a discordant tracer pattern of per- region and/or per-lesion distribution of recurrent disease was observed, while in four patients a concordant pattern was noted (no lesions were detected by either modality in the remaining four patients). Conclusion Neither 18 F-FDG nor 68 Ga-DOTATATE PET/ CT can fully map the extent of disease in patients with recurrent MTC, although 18 F-FDG PET/CT may identify more lesions. However, 68 Ga-DOTATATE PET/CT can be a useful complementary imaging tool and may identify patients suitable for consideration of targeted radionuclide somatostatin analogue therapy. Keywords Medullary thyroid carcinoma . Positron emission tomography . 18 F-fluorodeoxyglucose . 68 Ga-DOTATATE An Editorial Commentary on this paper is available at http://dx.doi. org/10.1007/s00259-009-1247-1 N. D. Papathanasiou : V. Prakash : I. Kayani : J. B. Bomanji (*) Institute of Nuclear Medicine, University College Hospital, 235 Euston Road, London NW1 2BU, UK e-mail: jamshed.bomanji@uclh.nhs.uk B. G. Conry Department of Radiology and Nuclear Medicine, Pembury Hospital, Tunbridge Wells, UK M. Caplin Department of Gastroenterology, Royal Free Hospital, London, UK S. Mahmood Singapore PET and Cardiac Imaging Centre, Singapore 238859, Singapore Eur J Nucl Med Mol Imaging (2010) 37:49–57 DOI 10.1007/s00259-009-1204-z