Diagnostic Performance of 18 F-FDG PET/CT in Papillary Thyroid Carcinoma with Negative 131 I-WBS at first Postablation, Negative Tg and Progressively Increased TgAb Level

Differentiated thyroid cancer (DTC) patients with negative serum thyroglobulin (Tg), negative 131I whole–body scintigraphy (131I-WBS) at first post-ablation and progressively increased TgAb level are a relatively rare entity in the follow-up after total thyroidectomy and radioactive iodine therapy. The value of 18F-FDG PET/CT in detecting the recurrence of disease in these patients has only been reported in a small case series. The goal of this study was to investigate the diagnostic accuracy of 18F-FDG PET/CT in detecting recurrent disease in these specific PTC patients and to identify risk factors for patients with positive 18F-FDG PET/CT results. Eighty-two PTC patients who had 18F-FDG PET/CT scans with negative Tg, negative 131I-WBS at first post-ablation and progressively increased TgAb levels were included. We found that the sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of 18F-FDG PET/CT in this patient group were determined as 84%, 72%, 92%, 57% and 82%, respectively. 18F-FDG PET/CT scan had a good diagnostic performance and should be performed routinely in PTC patients with negative Tg, negative 131I-WBS at first postablation and progressively increased TgAb level, especially when span for progressively increased TgAb level ≥ 3 years and/or progressively increased TgAb value up to 150 IU/mL.