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

Abstract

Background: The aim of this study is to evaluate the clinical role of 18F-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 131I 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 131I treatment, and subsequently presented with elevated serum thyroglobulin but negative 131I 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 surgery, 1 patient received radiation therapy of bone metastasis and the remaining patient received alcohol injection of metastatic neck lymph node. In 6 patients with negative finding on FDG PET-CT, 3 patients developed neck recurrence within 12 months after PET study. In our study, the sensitivity of FDG PET-CT was not improved by high serum TSH level. Conclusion: FDG PET-CT is a reliable method for detecting recurrence in patients with well-differentiated thyroid cancer with elevated serum thyroglobulin and negative 131I whole body scan.