Comparison of F-DOPA, F-FDG and Ga-somatostatin analogue PET/CT in patients with recurrent medullary thyroid carcinoma.

Purpose: To retrospectively evaluate and compare F-FDG, F-DOPA and Ga-somatostatin analogues for PET/CT in patients with residual/recurrent medullary thyroid carcinoma (MTC) suspected on the basis of elevated serum calcitonin levels. Methods: Included in the study were 18 patients with recurrent MTC in whom functional imaging with the three tracers was performed. The PET/CT results were compared on a per-patient basis and on a per-lesion-basis. Results: At least one focus of abnormal uptake was observed on PET/CT in 13 patients with F-DOPA (72.2% sensitivity), in 6 patients with Ga-somatostatin analogues (33.3%) and in 3 patients with F-FDG (16.7%) ( p < 0.01). There was a statistically significant difference in sensitivity between F-DOPA and F-FDG PET/CT ( p < 0.01) and between F-DOPA and Ga-somatostatin analogue PET/CT ( p = 0.04). Overall, 72 lesions were identified on PET/CT with the three tracers. F-DOPA PET/CT detected 85% of lesions (61 of 72), Ga-somatostatin analogue PET/CT 20% (14 of 72) and F-FDG PET/CT 28% (20 of 72). There was a statistically significant difference in the number of lymph node, liver and bone lesions detected with the three tracers ( p < 0.01). In particular, post-hoc tests showed a significant difference in the number of lymph node, liver and bone lesions detected by F-DOPA PET/CT and F-FDG PET/CT ( p < 0.01 for all the analyses) and by F-DOPA PET/CT and Ga-somatostatin analogue PET/CT ( p < 0.01 for all the analyses). The PET/CT results led to a change in management of eight patients (44%). Conclusion: F-DOPA PET/CT seems to be the most useful imaging method for detecting recurrent MTC lesions in patients with elevated serum calcitonin levels, performing better than F-FDG and Ga-somatostatin analogue PET/CT. F-FDG may complement F-DOPA in patients with an aggressive tumour. [ABSTRACT FROM AUTHOR]