FAP and digestive system neoplasm: In contrast, high FAP expression in matrix components of gastrointestinal tumors and metastatic tumors (9), rapid clearance by the kidney, less physiological uptake in normal organs, and high tumor-to-background ratio render [68Ga]Ga-FAPI-04 more advantageous for abdominal and pelvic imaging (5, 10, 16, 24).