FDG PET-CT in Patients with Recurrent Thyroid Cancer with Elevated Serum Thyroglobulin but Negative Iodine-131 Whole Body Scan

Background: The aim of this study is to evaluate the clinical role of 18 F-FDG (FDG) PET-CT in detecting recurrent or metastatic lesions in patients with well-differentiated thyroid cancer who have elevated serum thyroglobulin level but negative 131 I whole body scan. Methods: A retrospective study was performed in 23 patients with recurrent well-differentiated thyroid cancer who underwent FDG PET-CT in our institute from August 2003 to November 2006. All of these patients had received total thyroidectomy and 131 I treatment, and subsequently presented with elevated serum thyroglobulin but negative 131 I whole body scan. Among these 23 patients, 8 patients performed FDG PET-CT during high thyroid stimulating hormone (TSH) level and 15 patients performed FDG PET-CT during low TSH level. In all patients, results of FDG PET-CT were correlated with conventional images, histopathological findings and clinical follow-up. Results: FDG PET-CT showed positive findings in 17 of 23 patients, giving a sensitivity of 74%. There were altogether 25 metastatic lesions being detected in these 17 patients, which comprised of 14 neck lesions, 3 mediastinal lesions, 4 lung lesions, 3 bone lesions and 1 soft tissue lesion. FDG PET-CT led to a change in management in 8 patients, in whom 6 patients received