18F-FDG PET, somatostatin receptor scintigraphy, and CT in metastatic medullary thyroid carcinoma: a clinical study and an analysis of the literature

AIM: To determine the clinical potential of 2-Ffluoro-2-deoxy-D-glucose positron emission tomography (F-FDG PET) in patients with medullary thyroid carcinoma (MTC), we compared it to computed tomography (CT), and somatostatin receptor scintigraphy (SRS). PATIENTS AND METHODS: Blinded evaluation of PET, CT and SRS images obtained from 26 patients with histologically proven metastatic MTC was done by nuclear medicine and radiology specialists. Sites of tumour involvement were classified as "sure" or "suspicious". The data were analysed in comparison to two different standards. Either those sites classified as "sure" by at least one of the methods were defined as the standard or those sites of involvement which were classified as "sure" by at least two methods. RESULTS: Dependent on the type of data analysis performed, PET was able to demonstrate 56.8%/80.6% of the tumour sites, CT showed 64.5%/79.6%, and SRS showed 47.5%/69.9% of the tumour sites. CONCLUSION: Overall, CT is similar or better than PET in our patients (dependent on the standard) while SRS is inferior to both other techniques. Our data are in agreement with publications that consider CT superior to PET in the diagnosis of metastatic MTC while other studies show superiority of PET. However, a combination of CT and PET seems to be the most appropriate non-invasive diagnostic approach in patients with MTC.