Comparison of 68Ga-DOTATATE and 18F-fluorodeoxyglucose PET/CT in the detection of recurrent medullary thyroid carcinoma
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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 68Ga-DOTATATE and conventional 18F-FDG positron emission tomography/computed tomography (PET/CT).
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 68Ga-DOTATATE and 18F-FDG PET/CT within a maximum interval of 4 weeks (median interval of 1 week). 68Ga-DOTATATE- and 18F-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 68Ga-DOTATATE and 18F-FDG PET/CT findings 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 radiotracers. A separate analysis of the unenhanced CT component of the examination was performed. Verification of the lesions was achieved by histopathological analysis, further imaging studies and clinical follow-up.
68Ga-DOTATATE PET/CT imaging achieved disease detection in 13 of 18 and 18F-FDG PET/CT in 14 of 18 patients. These results corresponded to per-patient sensitivities of 72.2% [95% confidence interval (CI): 46.4–89.3%] for 68Ga-DOTATATE versus 77.8% (95% CI: 51.9–92.6%) for 18F-FDG (non-significant difference). 18F-FDG revealed a total of 28 metastatic MTC regions and 68Ga-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).
Neither 18F-FDG nor 68Ga-DOTATATE PET/CT can fully map the extent of disease in patients with recurrent MTC, although 18F-FDG PET/CT may identify more lesions. However, 68Ga-DOTATATE PET/CT can be a useful complementary imaging tool and may identify patients suitable for consideration of targeted radionuclide somatostatin analogue therapy.
KeywordsMedullary thyroid carcinoma Positron emission tomography 18F-fluorodeoxyglucose 68Ga-DOTATATE
Conflicts of interest
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