The great potential of novel imaging agent in the diagnosis of gallbladder cancer: a prospective study comparing [68Ga]Ga-FAPI-04 and [18F]FDG

Background: Gallbladder cancer (GBC) is an aggressive malignancy with poor prognosis. Accurate staging is critical for treatment planning, but [¹⁸F]FDG PET/CT has limited value due to high hepatic background and difficulty distinguishing inflammation from malignancy. [⁶⁸Ga]Ga-FAPI-04 PET/CT offers higher tumor-to-background contrast and low physiological uptake in normal tissues. This study was to investigate the value and the impact on clinical staging management of [ ⁶⁸ Ga]Ga-FAPI-04 comparing with [ ¹⁸ F]FDG PET/CT in patients with gallbladder cancer. This prospective study recruited patients who underwent ultrasound or MRI and were considered to have primary or recurrence GBC. All patients underwent [ ⁶⁸ Ga]Ga-FAPI-04 and [ ¹⁸ F]FDG PET/CT within one week of each other. Final histopathology, imaging, and follow-up results were used as reference standards. The tumor/background ratio (TBR) and maximum standardized uptake (SUVmax) between [ ⁶⁸ Ga]Ga-FAPI-04 and [ ¹⁸ F]FDG in primary tumors, distant metastases, lymph nodes, and peritoneal metastases were used to compare the difference. Results: A total of 17 patients were included in the study, of whom 13 patients with primary tumors of GBC were positive for [ ⁶⁸ Ga]Ga-FAPI-04 (100% detection rate), while [ ¹⁸ F]FDG detected 12 of them (92% detection rate). [ ⁶⁸ Ga]Ga-FAPI-04 was more sensitive than [ ¹⁸ F]FDG in detecting distant metastases (100% VS. 81%), lymph node metastases (99% VS. 94%) and peritoneal metastases (100% VS. 18%) of GBC. Also [ ⁶⁸ Ga]Ga-FAPI-04 had higher SUVmax for distant metastases and lymph nodes than [ ¹⁸ F]FDG. There was no significant difference in the uptake of the two tracers in the primary tumors,but the TBR values were significantly higher in ^{[ 68 Ga]Ga-FAPI-04 than in [ 18 F]FDG . Also [ 68 Ga]Ga-FAPI-04 identified far more peritoneal metastases than those identified by [ 18 F]FDG. Finally, the staging of two patients was revised upward because of the [ 68 Ga]Ga-FAPI-04 results, while the staging of the other two patients was revised downward. Conclusions: [ 68 Ga]Ga-FAPI-04 is more advantageous than [ 18 F]FDG in detecting primary tumors, distant metastases, lymph node metastases, and peritoneal metastases in GBC with higher SUVmax and TBR. Also [ 68 Ga]Ga-FAPI-04 is more promising for staging of GBC.}