Novel FAP ligands enable improved imaging contrast in sarcoma patients due to FAPI-PET/CT

A high expression of fibroblast activation protein (FAP) was observed in multiple sarcomas, indicating an enormous potential for PET/CT using ${}^{68}$Ga-radiolabeled inhibitors of FAP (FAPI). Therefore, this retrospective study aimed to evaluate the role of the novel hybrid imaging probe for sarcomas as a first clinical evaluation. A cohort of 15 patients underwent ${}^{68}$Ga-FAPI-PET/CT for staging or restaging. The acquisition of PET scans was performed 60 min after administration of 127 to 308 MBq of the tracer. The uptake of ${}^{68}$Ga-FAPI in malignant tissue as well as in healthy organs was quantified by standardized uptake values SUVmean and SUVmax. Excellent tumor-to-background ratios (> 7) could be achieved due to low background activity and high SUVmax in primary tumors (median 7.16), local relapses (median 11.47), and metastases (median 6.29). The highest uptake was found for liposarcomas and high-grade disease (range 18.86-33.61). A high SUVmax (> 10) was observed for clinically more aggressive disease. These preliminary findings suggest a high potential for the clinical use of ${}^{68}$Ga-FAPI-PET/CT for patients diagnosed with sarcoma.