The Value of FAPI PET/CT in Cholangiocarcinoma and Pancreatic Cancer: An Update.

To date, contrast-enhanced CT (ceCT), magnetic resonance imaging (MRI), and, in selected cases, F-fluorodeoxyglucose positron emission tomography/computed tomography (F-FDG PET/CT) are the current standard imaging modalities for staging of pancreatic cancer and cholangiocarcinoma. Fibroblast activation protein alpha (FAP) has gained interest as a promising molecular imaging target, particularly in tumors with a pronounced desmoplastic reaction such as pancreatic cancer and cholangiocarcinoma. Radiolabeled FAP inhibitors (FAPIs) enable noninvasive visualization of cancer using PET/CT. Recent studies have demonstrated that FAPI PET/CT provides superior sensitivity compared to ceCT and F-FDG PET/CT in cholangiocarcinoma and pancreatic cancer for detecting primary tumors, lymph node involvement, and distant metastases, particularly in hepatic metastases due to low physiological background uptake. Furthermore, FAPI PET/CT has been shown to affect TNM staging and subsequently alter treatment-decision making. Beyond staging, early evidence suggests a prognostic potential of FAPI PET/CT in tumor grading, therapy response assessment, and survival outcomes, although data remain limited. On the other hand, FAPI PET/CT comes with limitations, particularly in the context of fibrotic and inflammatory processes such as liver cirrhosis, pancreatitis, or primary sclerosing cholangitis, which may result in false-positive findings. This review summarizes the current clinical evidence for FAPI PET/CT in pancreatic cancer and cholangiocarcinoma, with a focus on diagnostic performance, prognostic relevance, therapeutic implications, and potential pitfalls.