Endocrine Abstracts (2006) 11 P532

The value of fluorine-18 fluorodeoxyglucose PET during follow-up of patients with medullary thyroid carcinoma

GA Lupoli1, S Colarusso1, A Panico1, F Fonderico1, F Nappi1, F Marciello1, A Gonnella1, MR Poggiano1, E Nicolai2, M Salvatore2 & G Lupoli1

1Department of Molecular and Clinical Endocrinology and Oncology - University Federico II, Naples, Italy; 2Department of Functional and Biomorphological Sciences, University Federico II, Naples, Italy.

Introduction: Fluorine-18 fluorodeoxyglucose positron emission tomography (18F-FDG PET) is an innovative method for the detection of primary tumours or metastases of thyroid cancer; however, recurrence or metastases of medullary thyroid carcinoma (MTC) are still difficult to detect.

Aim: The objective of this study was to evaluate the clinical use of 18F-FDG PET in patients with MTC.

Patients and methods: We enrolled 11 patients with MTC, presenting elevated serum calcitonin levels during post-surgical follow-up. They underwent 18F-FDG PET and conventional imaging techniques: ultrasonography (US), magnetic resonance (MR), computerized tomography (CT), 111In-DTPA-Phe-octreotide (Octreoscan), 131I-MIBG scintigraphy.

Results and discussion: 18F-FDG PET was positive in 7 cases: 2 of them were false positive results - 1 due to pneumonia and 1 to post-surgical fibrosis in the thyroid bed. In the remaining 5 patients, 18F-FDG PET detected tumour foci, confirmed also by CT, MR, Octreoscan and 131I-MIBG scintigraphy in 4, and by histology in 1 of them. 4 patients showed completely negative 18F-FDG PET scans: 2 results were true negative, as confirmed also by other techniques, whereas 2 were false negative (in the first one a secondary lesion localized in the pulmonary region was detected only by CT, while in the second loco-regional lymph node metastases were correctly identified by Octreoscan).

18F-FDG PET was able to identify the metastatic foci as efficiently as the conventional imaging techniques and to localize a previously unknown tumour relapse in one patient; nevertheless, 2 false positive and 2 false negative results were recorded.

Conclusion: 18F-FDG PET appears to be a valuable and useful tool when used in association with other morphological and functional diagnostic imaging techniques during the follow-up of MTC patients with increased serum tumour markers.