An efficacious opportunity for diagnosis and treatment of cancers: Radiolabeled fibroblast activation protein (FAP) inhibitors

Despite the revolutionized diagnostic effect of fluorine-18 -fludeoxyglucose ([¹⁸F]-FDG) as a positron emission tomography (PET) radiotracer in oncological divisions, lack of specificity and sensitivity in discovery of some tumor subtypes was inevitable. Fibroblast activation protein (FAP) is overexpressed in a vast majority of neoplasms, particularly in more than 90% of epithelial tumors which could be an appropriate target for evaluation of tumor's molecular and metabolic functions by FAP inhibitor (FAPI) ligands. Considerably extensive radiolabeled FAPIs have been investigated during clinical trials for diagnostic as well as theranostic applications with encouraging outcomes. In the same cancers, PET/CT imaging by FAPIs are demonstrating to be valuable alternative to [¹⁸F]-FDG in assessment of cancers in which [¹⁸F]-FDG PET performance is suboptimal due to [¹⁸F]-FDG high background uptake or relatively low avidity. Furthermore, the propensity to specifically target FAP expression through FAP-targeted medications or radiotracer therapy creates prospects for image-guided treatment in both cancer and non-cancer indications. FAPI PET will remain a fascinating field of study in the future years.