Abstract
Positron emission tomography (PET) is an integral part of the imaging of solid tumors in today's oncology practice. The most commonly used PET radiotracer is 18F-Fluorodeoxyglucose (18F-FDG). FDG PET has imaging characteristics of a high tumor-to-background uptake ratio and is used in the detection of primary as well as metastatic sites. However, a significant pitfall is its inability to differentiate between neoplastic and infective lesions. To address this concern, many PET radiotracers have been developed and tried over time, a promising one being radiolabelled fibroblast activation protein inhibitor (FAPI). Fibroblast-activated protein (FAP) is a type II transmembrane glycoprotein expressed by cancer-associated fibroblasts (CAFs); it forms a significant component of the tumor stroma. Since there is over-expression of CAF in the majority of malignancies, it is a potential target for molecular imaging using PET. Several radiolabeled FAP inhibitors have been developed for PET imaging of malignancies and have also been used in theranostic applications.