Characterizing Inflammatory Bowel Disease With 68Ga-FAPI PET/CT

68Ga-FAPI has been developed as a tumor-targeting agent as fibroblast activation protein is overexpressed in cancer-associated fibroblasts and some inflammation,such as inflammatory bowel disease. And it might be more sensitive than FDG in detecting a certain type of inflammations according to our preliminary research. Thus this prospective study is going to investigate whether 68Ga-FAPI PET/CT may be superior for diagnosis, therapy response assessment and follow-up of inflammatory bowel disease than 18F-FDG PET/CT.

Inflammatory bowel disease (IBD) is comprised of two major disorders: ulcerative colitis (UC) and Crohn's disease(CD).CD is an autoimmune condition resulting in chronic gut inflammation that can be complicated by intestinal fibrosis and stricture formation. Ulcerative colitis is characterized by recurring episodes of inflammation limited to the mucosal layer of the colon. It commonly involves the rectum and may extend in a proximal and continuous fashion to involve other parts of the colon. Studies identified FAP to be overexpressed in uninflamed strictures compared with nonstrictured colonic regions in biopsies taken from Crohn's disease patients. But preliminary studies showed FAP was not overexpressed in colonic biopsies taken from healthy individuals or individuals with ulcerative colitis.68Ga-FAPI has been developed as a tumor-targeting agent as fibroblast activation protein is overexpressed in cancer-associated fibroblasts and inflammation. Recently we have published an article of the application of 68Ga-FAPI in IgG4-related disease which showed it was more sensitive than FDG in detecting a certain type of inflammations. Thus this prospective study is going to investigate whether 68Ga-FAPI PET/CT may be superior for diagnosis, therapy response assessment and follow-up of IBD than 18F-FDG PET/CT.

Intravenous injection of one dosage of 74-148 MBq (2-4 mCi) 68Ga-FAPI. Tracer doses of 68Ga-FAPI will be used to image lesions of inflammatory bowel disease by PET/CT.

Sensitivity and Specificity of 68Ga-FAPI PET/CT for inflammatory bowel disease in comparison with 18F-FDG PET/CT

Correlation between Total Lesion Glycolysis (TLG) of bowel lesions assessed on 68Ga-FAPI PET/CT and clinical parameters for inflammatory bowel disease

Inclusion Criteria: suspected or confirmed untreated inflammatory bowel disease patients; 18F-FDG PET/CT within two weeks; signed written consent. Exclusion Criteria: pregnancy; breastfeeding; known allergy against FAPI any medical condition that in the opinion of the investigator may significantly interfere with study compliance.

Luo Y, Pan Q, Xu H, Zhang R, Li J, Li F. Active uptake of 68Ga-FAPI in Crohn's disease but not in ulcerative colitis. Eur J Nucl Med Mol Imaging. 2021 May;48(5):1682-1683. doi: 10.1007/s00259-020-05129-7. Epub 2020 Nov 27. No abstract available.