Here, we present the first study evaluating a quinoline-based FAP inhibitor bound to a DOTA chelator [68Ga]Ga-FAPI-04 versus [18F]FDG for real-time PET-based biology-guided radiation therapy in a variety of cancer types, including pancreatic cancer, liver cancer, lung cancer, head and neck, and cervical cancer. Here, FAP is linked to pancreatic neoplasm.