Role of Fluorine 18 Fluorodeoxyglucose (FDG) Positron Emission Tomography (PET)/Computed Tomography (CT) in Detection of Post-Thyroidectomy Recurrence in Differentiated Thyroid Cancer

Abstract

Aim: To demonstrate the role of 18F-FDG PET/CT for detection of post-thyroidectomy recurrence in differentiated cancer thyroid patients with negative radio-isotope iodine scan, yet showing elevated serum thyroglobulin level. Procedure: This is a prospective study which included 20 patients who had previous history of differentiated cancer thyroid. All patients after history taking and revising the medical sheet underwent Serum Thyroglobulin level Estimation & entire body scan I-131 (WBS) examination and then 18F-FDG PET/CT study. The findings of PET/CT imaging were compared with histopathology results or clinical follow-up results as a gold standard. Results: FDG PET/CT based analysis showed that 19 true positives and 1 was true negative as confirmed by the gold standard (Histopathology and clinical follow-up). 13 patients had either local recurrence or lymph node metastases without distant metastatic disease, 6 patients had different distant metastasis. 18F-FDG PET/CT based analysis showed that 19 true positives and 1 was true negative as confirmed by the gold standard (Histopathology and clinical follow-up). The sensitivity and accuracy of PET/CT (95%) were significantly better than those of the CT alone (84.2% and 80%, respectively) [P=0.03]. Conclusion: Combination between positron emission tomography (PET) and computed tomography (CT) allow anatomic, functional & molecular information. 18F-FDG PET/CT provided a critical role in assessment and management of patients with suspected differentiated thyroid recurrence, presenting with high serum thyroglobulin level and negative radio-isotope scan. The 18F-FDG PET/CT enhance diagnostic accuracy through giving exact anatomical localization of recurrent and/or metastatic tumor foci.