Characterization of the benign lesions with increased 68 Ga-FAPI-04 uptake in PET/CT

Objectives The objective of the study was to characterize benign lesions showing increased 68 Ga-FAPI-04 uptake on FAPI PET/CT. Methods We retrospectively reviewed 182 patients with suspected various cancers who were performed 68 Ga-FAPI-04 PET/CT imaging from August 2020 to December 2020. The diagnoses of the benign lesions were made by the CT findings (CT), other imaging information (OII) (contrast enhance CT, FDG PET, ultrasound, MRI or others), clinical information (CI) (medical history, laboratory examination, symptom, physical sign and follow-up information) or histological biopsy (HB). Results A total of 185 primary malignant tumors were detected by FAPI PET/CT with the median SUV max of 9.0 (range from 0.97 to 25.71). There were 360 benign lesions with increased FAPI uptake were detected in 146 (146/182, 80.2%) patients with the median SUV max of 3.64 (range from 1.39 to 21.56), including inflammatory processes ( n = 231, 64.2%), exostosis ( n = 54, 15%), hemorrhoid ( n = 47, 13.1%), fracture ( n = 17, 4.7%), hepatic fibrosis ( n = 4, 1.1%), and others ( n = 7, 1.9%). Conclusion Benign lesions with increased 68 Ga-FAPI-04 uptake are common. The overall SUV max of benign lesions is lower than that of malignant tumors, however there is a large overlap of SUV max range. Similar to FDG PET, some benign lesions can be easily diagnosed by combining CT findings, special location and clinical data, but there are still some lesions that may be confused with malignant lesions, which need to be paid more attention. Trail registration NIH ClinicalTrials.gov (NCT04499365).