[Use of 18F FDG-PET in patients with suspicion of recurrent differentiated thyroid cancer by elevated antithyroglobulin antibodies levels and negative ¹³¹I scan].

AIM: To evaluate the utility of (18F)FDG-PET for patients diagnosed of differentiated thyroid carcinoma who present risk of disease and invaluable levels of thyroglobulin (Tg) by the presence of antibodies antithyroglobulin (AbTg).

MATERIAL AND METHODS: Retrospective study of 7 women of 40 years old and histological diagnosis of differentiated thyroid cancer (7 papillary tumours) that were sent to our department for the accomplishment of(18F)FDG-PET study because of suspicion of disease, due to ¹³¹I negative and high levels of AbTg, between the year 2002 and 2007. 11 PET scans were obtained after the intravenous injection of 370-434 MBq of (18F)FDG in normoglycemia conditions and previous administration of muscle relaxant, hydration and diuretic. The results of (18F)FDG-PET scans were confirmed by pathologic examination or clinical outcome and radiographic examination for more than 24 months.

RESULTS: The prevalence of recurrence in our population was 57.14%. All patients presented levels of Tg lower than 3 ng/dl and AbTg superior to 200 UI/ml. Three patients had precedent thyroiditis. Out of 11 scans performed 3 of them were negative and 8 cases were found positive. It ruled out the existence of disease in three patients and localized the presence of recurrence in 4 patients.

CONCLUSION: (18F)FDG-PET CONCLUSION: 18F-FDG-PET is a useful diagnostic tool for the detection of recurrence as well as to rule out the existence of disease with a high accuracy, in patients with differentiated thyroid carcinoma with ¹³¹I whole body scan negative but with pathological elevation of antithyroglobulin antibodies.