Value of 18F-fluorodeoxyglucose positron emission tomography combined with computed tomography in staging of patients with differentiated thyroid cancer after thyroidectomy during the first course of radioiodine therapy

The study objective is to evaluate value of 18F-fluorodeoxyglucose positron emission tomography combined with computed tomography (PET-CT) and whole-body scintigraphy (131I-WBS) performed during the first course of radioiodine therapy for its ability to detect persistence metastatic foci and for its role in the management of differentiated thyroid cancer patients.

Materials and methods. Forty patients with DTC underwent both post-therapeutic 131I-WBS and PET-CT. PET-CT performed on a positron emission tomograph combined with a 16-slice computer tomograph. Post-therapeutic 131I-WBS performed during radioiodine therapy on the single-detector gamma camera.

Results. Sensitivity in detecting of the tumor persistence for PET-CT was 84 %, for post-therapeutic 131I-WBS 66 % (р >0.05). In 17 (42.5 %) patients additional PET-CT foci were found that negative on 131I-WBS, including 11 (27.5 %) cases of distant metastases. Fifteen percent of patients had metastatic foci visualized only on 131I-WBS, including 4 (10 %) cases of distant metastases. In 17 (44 %) patients tumor foci were identified by both methods. A high pre-ablative level of stimulated thyroglobulin was the only independent predictor of the presence of PET-CTpositive metastatic foci (p = 0.001).

Conclusion. 18F-fluorodeoxyglucose PET-CT can be recommended during the first radioiodine therapy in differentiated thyroid cancer patients with a high risk progression group, as well as with suspected the tumor persistence in case of a high pre-ablation thyroglobulin level, to complete staging, improve the quality of management and ongoing risk stratification.

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