Tumor Burden of Iodine-Avid Bone Metastatic Thyroid Cancer Identified via 18 F-Sodium Fluoride PET/CT Imaging.

BACKGROUND: Patients with differentiated thyroid cancer (DTC) are referred to radioactive 131 I (RAI) therapy and post-therapy 131 I whole-body scintigraphy (WBS) to identify local and/or remote metastases. Positron emission tomography (PET)/computed tomography (CT) imaging with 18 F-fluoro-D-glucose (FDG) or 18 F-sodium fluoride (NaF) may also be used with these patients for the evaluation of bone metastases. We compared the role of 18 F-NaF PET/CT and 18 F-FDG-PET/CT in patients with DTC and documented bone metastases at post-therapy WBS.

METHODS: Ten consecutive DTC patients with iodine avid bone metastasis at post-therapy WBS referred to 18 F-NaF PET/CT and 18 F-FDG PET/CT were studied. The findings of the three imaging procedures were compared for abnormal detection rates and concordance.

RESULTS: At post-therapy 131 I WBS, all patients had skeletal involvement with a total of 21 bone iodine avid lesions. At 18 F-FDG PET/TC, 19 bone lesions demonstrated increased tracer uptake and CT pathological alterations, while 2 lesions did not show any pathological finding. At 18 F-NaF PET/CT, the 19 bone lesions detected at 18 F-FDG PET/TC also demonstrated abnormal tracer uptake, and the other 2 bone iodine avid foci did not show any pathological finding.

CONCLUSIONS: In patients with DTC, 18 F-NaF PET/CT did not obtain more information on the metastatic skeletal involvement than post-therapy 131 I WBS and 18 F-FDG PET/CT.