The value of 18F-DOPA PET-CT in patients with medullary thyroid carcinoma: comparison with 18F-FDG PET-CT.

The purpose of this prospective study was to compare the value of DOPA PET-CT with FDG PET-CT in the detection of malignant lesions in patients with medullary thyroid carcinoma (MTC). Twenty-six consecutive patients (10 men, 16 women, mean age 59 +/- 14 years) with elevated calcitonin levels were evaluated in this prospective study. DOPA and FDG PET-CT modalities were performed within a maximum of 4 weeks (median 7 days) in all patients. The data were evaluated on a patient- and lesion-based analysis. The final diagnosis of positive PET lesions was based on histopathological findings and/or imaging follow-up studies (i.e., DOPA and/or FDG PET-CT) for at least 6 months (range 6-24 months). In 21 (21/26) patients at least one malignant lesion was detected by DOPA PET, while only 15 (15/26) patients showed abnormal FDG uptake. DOPA PET provided important additional information in the follow-up assessment in seven (27%) patients which changed the therapeutic management. The patient-based analysis of our data demonstrated a sensitivity of 81% for DOPA PET versus 58% for FDG PET, respectively. In four (4/26) postoperative patients DOPA and FDG PET-CT studies were negative in spite of elevated serum calcitonin and CEA levels as well as abnormal pentagastrin tests. Overall 59 pathological lesions with abnormal tracer uptake were seen on DOPA and/or FDG PET studies. In the final diagnosis 53 lesions proved to be malignant. DOPA PET correctly detected 94% (50/53) of malignant lesions, whereas only 62% (33/53) of malignant lesions were detected with FDG PET. DOPA PET-CT showed superior results to FDG PET-CT in the preoperative and follow-up assessment of MTC patients. Therefore, we recommend DOPA PET-CT as a one-stop diagnostic procedure to provide both functional and morphological data in order to select those patients who may benefit from (re-)operation with curative intent as well as guiding further surgical procedures.