Fibroblast activation protein (FAP) is expressed by many cancer-associated fibroblasts, having a pivotal role in many desmoplastic tumor histotypes (sarcoma, pancreatic cancer, colorectal cancer). 68Ga-FAPI inhibitor (FAPI) is a promising novel molecular imaging tracer for positron emission tomography with computed tomography (PET/CT), with favorable initial results in different tumor entities. Compared to 18F-FDG, 68Ga-FAPI PET/CT shows a similar biodistribution, with less background tracer uptake in the brain, oral mucosa and liver, thus making this tracer potentially suitable to detect tumor lesions in these regions.~Moreover, the FAPI ligand contains a DOTA peptide which makes it appropriate also for therapeutic options if linked with 177Lutetium or 90Yttrium.~There is an increasing number of trials aimed to assess the efficacy and the clinical impact of 68Ga-FAPI PET/CT. Therefore, the inter-observer agreement and variability with 68Ga-FAPI PET/CT need to be established.
The aim of the present study is to evaluate the interobserver agreement for FAPI PET/CT interpretations of representative cancer types and compare findings among readers with different levels of experience.