Performance and Prospects of [(68)Ga]Ga-FAPI PET/CT Scans in Lung Cancer

SIMPLE SUMMARY: The purpose of this review was to provide an overview of all the available evidence regarding the use of fibroblast activation protein inhibitor (FAPI) as a tracer for positron emission tomography (PET) in patients with lung cancer. In several studies and case reports, radioisotope-labelled FAPI PET/CT showed a strong diagnostic performance in lung cancer. In addition, the possible prognostic value of FAPI PET/CT in lung cancer is proposed. ABSTRACT: Fibroblast activation protein (FAP) could be a promising target for tumor imaging and therapy, as it is expressed in >90% of epithelial cancers. A high level of FAP-expression might be associated with worse prognosis in several cancer types, including lung cancer. FAPI binds this protein and allows for labelling to Gallium-68, as well as several therapeutic radiopharmaceuticals. As FAP is only expressed at insignificant levels in adult normal tissue, FAPI provides a highly specific tumor-marker for many epithelial cancers. In this review, current information on the use of [(68)Ga]Ga-FAPI PET/CT in lung cancer is presented. [(68)Ga]Ga-FAPI shows a high uptake (standardized uptake value = SUV(max)) and tumor-to-background ratio (TBR) in primary lung cancer lesions, as well as in metastatic lesions of other tumor types located in the lung and in lung cancer metastases located throughout the body. Where a comparison was made to [(18)F]FDG PET/CT, [(68)Ga]Ga-FAPI showed a similar or higher SUV(max) and TBR. In brain and bone metastases, [(68)Ga]Ga-FAPI PET/CT outperformed [(18)F]FDG PET/CT. In addition to this strong diagnostic performance, a possible prognostic value of [(68)Ga]Ga-FAPI PET/CT in lung cancer is proposed.