Role of [F]FAPI-04 in staging and therapeutic management of intrahepatic cholangiocarcinoma: prospective comparison with [F]FDG PET/CT.

BACKGROUND

Fluorine-18 fluorodeoxyglucose ([F]FDG) positron emission tomography/computed tomography (PET/CT) has some limitations in diagnosis of Intrahepatic cholangiocarcinoma (ICC).

MATERIALS AND METHODS

Patients with histologically confirmed ICC who underwent both [F]FDG and F-labeled fibroblast-activation protein inhibitors ([F]FAPI)-04 PET/CT were prospectively analyzed. The maximum standard uptake value (SUV), tumor-to-background ratio (TBR), metabolic tumor volume (MTV), total lesion glycolysis (TLG), [F]FAPI-avid tumor volume (FTV), total lesion fibroblast activation protein expression (TLF) were compared between the two modalities by paired Wilcoxon signed-rank test and Mann-Whitney U test, and McNemar's test was used to assess the diagnostic accuracy between the two techniques.

RESULTS

In total, 23 patients with 389 lesions were included. Compared to [F]FDG, [F]F-FAPI-04 PET/CT demonstrated a higher detection rate for intrahepatic lesions (86.3% vs. 78.2% P = 0.040), lymph node metastases (85.2% vs. 68.2%, P = 0.007), peritoneal metastases (100% vs. 93.8%), and bone metastases (100% vs. 70.5%, P < 0.001). [F]FAPI-04 PET showed higher SUV, TBR and greater tumor burden values than [F]FDG PET in non-cholangitis intrahepatic lesions (SUV: 8.7 vs. 6.4, P < 0.001; TBR: 8.0 vs. 3.5, P < 0.001; FTV vs. MTV: 41.3 vs. 12.4, P < 0.001; TLF vs. TLG: 223.5 vs. 57.0, P < 0.001), lymph node metastases (SUV: 6.5 vs. 5.5, P = 0.042; TBR: 5.4 vs. 3.9, P < 0.001; FTV vs. MTV: 2.0 vs. 1.5, P = 0.026; TLF vs. TLG: 9.0 vs. 7.8 P = 0.024), and bone metastases (SUV: 9.7 vs. 5.25, P < 0.001; TBR: 10.8 vs. 3.0, P < 0.001; TLF vs. TLG: 9.8 vs. 4.2, P < 0.001). However, [F]FDG showed higher radiotracer uptake (SUV: 14.7 vs. 8.4, P < 0.001; TBR: 7.4 vs. 2.8, P < 0.001) than [F]FAPI-04 PET/CT for 6 patients with obstructive cholangitis. [F]FAPI-04 PET/CT yielded a change in planned therapy in 6 of 23 (26.1%) patients compared with [F]FDG.

CONCLUSIONS

[F]FAPI-04 PET/CT had higher detection rate and radiotracer uptake than [F]FDG PET/CT in intrahepatic lesions, lymph node metastases, and distant metastases, especially in bone. Therefore, [F]FAPI-04 PET/CT may be a promising technique for diagnosis and staging of ICC.

TRIAL REGISTRATION

Clinical Trials, NCT05485792. Registered 1 August 2022, retrospectively registered, https//clinicaltrials.gov/study/NCT05485792?cond=NCT05485792&rank=1.