Dual PET/CT with 18F-DOPA and 18F-FDG, in metastatic medullary thyroid carcinoma and rapidly increasing calcitonin levels: comparison with conventional imaging:

Background: To evaluate the role of a multi-imaging PET with F-18-DOPA and F-18-FDG in comparison with conventional imaging (CI) in recurrent medullary thyroid carcinoma (MTC). Methods: 18 MTC patients who had thyroidectomy were included; they presented with elevated and rapidly increasing calcitonin levels during follow up. Cl had revealed metastatic deposits in 9 patients. Patients were referred to us for a PET/CT with F-18-DOPA and F-18-FDG. Histologic/cytologic confirmation of recurrent MTC was obtained in at least one PET-positive lesion in all patients. Results: Foci of abnormal uptake were observed in 15 patients at F-18-DOPA and in 11 at F-18-FDG; 8 patients showed the same number of positive lesions with both tracers, 2 showed more lesions on F-18-FDG, I was positive at F-18-FDG alone and 5 at F-18-DOPA alone. In 3 patients with a DOPA-positive loco-regional relapse a re-operation with curative intent was offered. SUVmax values were higher for F-18-FDG compared to F-18-DOPA (mean 12.7 +/- 4.1 vs. 5.5 +/- 2.1, p < 0.05). Calcitonin was higher in PET-positive patients compared to PET negative ones, while no significant differences were observed between F-18-DOPA and F-18-FDG positive patients. Conclusions: In MTC patients with rapidly increasing calcitonin levels during follow up, F-18-DOPA has a good sensitivity and a complementary role with F-18-FDG PET/CT in detecting metastatic deposits. In our experience, the sensitivity of a multi-imaging F-18-DOPA & F-18-FDG PET/CT approach is greater than that obtained with CI. The higher SUVmax values found with F-18-FDG in some patients may reflect more aggressive tumors. (c) 2010 Elsevier Ltd. All rights reserved.