Prospective Evaluation of 68Ga-FAPI PET in Biliary Cancers

Biliary tract cancers frequently present at an advanced stage and require accurate staging to guide treatment decisions such as surgery, systemic therapy, or palliative management. Although 18 F-FDG PET/CT is widely used in clinical practice, its diagnostic performance is limited in detecting small primary lesions, nodal metastasis, liver metastasis, and peritoneal carcinomatosis. Gallium-68 Fibroblast Activation Protein Inhibitor (FAPI) PET/CT is a novel imaging technology that targets cancer-associated fibroblasts, which are abundant in the desmoplastic stroma characteristic of biliary tract cancers. Early evidence suggests that FAPI PET/CT may provide improved lesion detectability and tumor-to-background contrast compared to FDG PET/CT. This prospective observational study will evaluate the clinical utility of Ga-68 FAPI PET/CT for initial staging and suspected recurrence in patients with biliary tract cancers. Diagnostic performance metrics (sensitivity, specificity, PPV, NPV, and semi-quantitative PET parameters such as SUVmax and metabolic volume) will be assessed and compared with FDG PET/CT and/or follow-up imaging or histopathology as the gold standard. The study aims to determine the incremental diagnostic contribution of FAPI PET/CT and its potential impact on clinical decision-making. Findings from this research may help define the role of FAPI PET/CT as a complementary or alternative imaging modality in staging and restaging of biliary tract cancers and may support future prospective multicenter trials.