impact of ^18f-fdg pet/ct on treatment of patients with differentiated thyroid carcinoma, negative ^131i whole body scan and elevated serum thyroglobulin

Objective(s): ^18f-fdg pet/ct is increasingly performed in patients with differen-tiated thyroid cancer. the aim of this study was to assess the clinical impact of ^18f-fdg pet/ct on the management of patients with differentiated thyroid carcinoma who had elevated serum thyroglobulin (tg) and negative ^131i whole body scan (wbs) .methods: 67 patients with differentiated thyroid carcinoma were included in this study. the findings of ^18f-fdg pet/ct imaging were compared with histo-pathology, follow up imaging, or clinical follow-up results. the diagnostic accuracy of ^18f-fdg pet/ct was evaluated for the entire patient group and for those patients with stimulated serum thyroglobulin levels of less than 5, 5–10, and more than 10 pmol/l as well as for local recurrences and metastases sites. the impact of ^18f-fdg pet/ct on therapeutic management was also evaluated .results: 30/67 patients had positive findings on ^18f-fdg pet/ct; 28 were true-positive and 2 were false-positive. ^18f-fdg pet/ct results were true-negative in 36 patients and false-negative in 1 patient. the overall sensitivity, specificity, accuracy, ppv and npv of ^18f-fdg pet/ct were, 96.5%, 94.5%, 95.5%, 93.3%, and 97.2% respectively. positive ^18f-fdg pet/ct findings were directly correlated with stimulated serum thyroglobulin levels, 7.1% had tg between 5–10, and 92.9% had tg greater than 10 pmol/l. ^18f-fdg pet/ct had a high or moderate impact on treatment management in 28 (41.8%) of patients.conclusion: ^18f-fdg pet/ct is able to improve diagnostic accuracy and have management impact in a therapeutically relevant way in patients with differentiated thyroid carcinoma who present with rising thyroglobulin level, negative ^131i wbs, and clinical suspicion of recurrent disease.