Comparison of PSMA/FAPI Bispecific Tracer ¹⁸F-ALF-NOTA-PSFA-1 and ¹⁸F-FDG PET/CT in the Detection of Primary Clear Cell Sarcoma of Bone.

A 43-year-old man presented with left hip pain. Contrast-enhanced CT demonstrated lytic destruction of the left ilium and sacrum with associated soft-tissue extension, suggestive of a bone tumor. Subsequent ¹⁸F-FDG PET/CT revealed only mild or no FDG avidity in lesions involving the ilium, sacrum, and right fibula. In contrast, these lesions demonstrated intense or elevated uptake on PSMA/FAPI bispecific tracer ¹⁸F-ALF-NOTA-PSFA-1 PET/CT. These observations indicate that ¹⁸F-ALF-NOTA-PSFA-1 PET/CT holds considerable potential for sarcoma detection and may support the development of PSMA/FAPI bispecific targeted receptor radionuclide therapy.