Fibroblast activation protein (FAP) is a serine protease that belongs to the dipeptidyl peptidase-IV (DPP-IV) family located in fbroblast membranes. FAP is overexpressed in the cancer-associated fbroblasts (CAFs) of 90% of epithelial carcinomas, including primary and metastatic liver cancer. We aim to conduct a prospective study to investigate the diagnostic perfoemance of 18F-FAPI PET/CT in evaluating suspicious liver mass without FDG avidity.

Fibroblast activation protein (FAP) is a serine protease that belongs to the dipeptidyl peptidase-IV (DPP-IV) family located in fbroblast membranes. FAP is overexpressed in the cancer-associated fbroblasts (CAFs) of 90% of epithelial carcinomas, including primary and metastatic liver cancer. Therefore, FAP-targeted radiopharmaceuticals can be considered a promising approach for visualizing CAFs. CAFs are crucial components of the tumor stroma, promote the growth of cancer cells, and are associated with poor prognosis. Currently, 18F-labelled fbroblast activation protein inhibitor 18F-FAPI has shown promising diagnostic value in many types of tumors, especially those in which are not avid for 18F-FDF , and several studies have demonstrated that 18F-FAPI PET/CT is superior to 18F-FDG PET/CT for detecting liver cancer and has lower tracer uptake in normal liver tissue. We aim to conduct a prospective study to investigate the diagnostic performance of 18F-FAPI PET/CT in evaluating suspicious liver mass without FDG avidity.

Inclusion Criteria:

• patients with suspected liver malignant lesions based on traditional diagnostic imaging (CT or MRI or ultrasound) and clinical symptoms;
• patients underwent [18F]FDG PET/CT with negative findings (suspicious primary and/or metastatic lesions were hypo- or isometabolic on [18F]FDG PET/CT);
• patients who agreed to undergo [18F]FAPI PET/CT scans within 1 week.

Exclusion Criteria:

• pregnancy;
• age<18 years old;
• patients with chemo/radio/targeted therapy before scanning;
• inability to provide informed consent (signed by participant, parent, or legal representative).