The role of 68Ga-DOTATATE PET/CT and 18F-FDG PET/CT in the follow-up of patients with medullary thyroid cancer

Abstract

Objective: Medullary thyroid cancer (MTC) is an aggressive form of thyroid malignancy with local metastasis in 30%-50% of the cases and distant metastasis predominantly to lung, liver and skeleton in 13%-15% of patients. Identification of the lesion using imaging modalities is of crucial importance for disease management in the recurrent or metastatic MTC. In this study, we aimed to determine the efficacy of fluorine-18-fluorodeoxyglucose positron emission tomography/computed tomography (¹⁸F-FDG PET/CT) and gallium-68 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid tyrosine-3-octreotate (⁶⁸Ga-DOTATATE) PET/CT imaging in patients with MTC and to evaluate the relationship between imaging findings and serum tumor markers.

Materials and methods: The records of MTC patients, who were treated and followed-up in our department between the years 2005 and 2018 were retrospectively analyzed. Seventy-three patients with MTC, who underwent either ⁶⁸Ga-DOTATATE PET/CT (n=61) and/or ¹⁸F-FDG PET/CT (n=59) together with serum calcitonin (Ctn) and/or carcinoembryogenic antigen (CEA) measurement within 6 months period were included in the study. Gallium-68-DOTATATE PET/CT and ¹⁸F-FDG PET/CT scans performed within 6 months on the same patient (n=38) were analyzed separately for comparison of the efficacy of both modalities.

Results: The overall sensitivity of ¹⁸F-FDG PET/CT and ⁶⁸Ga-DOTATATE PET/CT were 72.4% and 88.1%, respectively in detecting recurrent or metastatic disease. In the group of patients, who had both ¹⁸F-FDG PET/CT and ⁶⁸Ga-DOTATATE PET/CT within 6 months interval (median: 1.14 months; range: 0.03 - 5.7 months), no significant difference was found in the overall sensitivity of both imaging modalities, however ⁶⁸Ga-DOTATATE PET/CT was found to be more sensitive in detection of bone lesions compared to ¹⁸F-FDG PET/CT (P=0.005).

Conclusion: Both ¹⁸F-FDG PET/CT and ⁶⁸Ga-DOTATATE PET/CT are efficient imaging modalities in detection of recurrent or metastatic disease in MTC patients. Gallium-68-DOTATATE PET/CT could be more beneficial in detection of bone metastases with respect to ¹⁸F-FDG PET/CT.