68Ga-FAPI-RGD PET/CT Detected Skull Metastasis Better Than 18F-FDG in a Patient With Radioiodine-Refractory Differentiated Thyroid Cancer

A 60-year-old woman underwent resection of a right humeral tumor 1 year ago, and postoperative pathology indicated metastatic papillary thyroid cancer. She had her first 131 I treatment after a total thyroidectomy. Subsequent whole-body imaging after 131 I administration revealed 131 I-avid metastases in the left parietal bone. These metastases were observed to be larger during her second 131 I treatment, conducted 6 months later. Consequently, the patient was diagnosed with radioiodine-refractory differentiated thyroid cancer. 68 Ga-FAPI-RGD PET/CT demonstrated higher tracer uptake and clearer lesion boundaries compared with 18 F-FDG PET/CT. This suggests that 177 Lu-FAPI-RGD could potentially serve as a treatment option for radioiodine-refractory differentiated thyroid cancer.