Radiolabeled FAP inhibitors as new pantumoral radiopharmaceuticals for PET imaging: a pictorial essay

Fibroblast activation protein (FAP)-targeted radiopharmaceuticals recently emerged as potential pantumoral agent for PET imaging. FAPi PET provides the opportunity to explore the tumor microenvironment, a highly heterogeneous and dynamic system of various non-malignant cells, by assessing the overexpression of FAP in cancer-associated fibroblasts. A significant increase in FAP expression can be found in several tumor subtypes, in which has been observed an increased tumor lesion uptake associated with low and favorable background, leading to a high detection rate of tumor location(s). This pictorial essay aims to present a selection of clinical cases highlighting the potential benefit of FAPi PET in different tumor subtypes, especially considering the higher diagnostic accuracy compared to FDG PET. We present clinical cases of breast cancer, lung cancer, gastric cancer, hepatocellular carcinoma, gynecological cancers and peritoneal carcinomatosis, as well as an introduction of the biodistribution of FAPi.