Influence of Cirrhosis on ⁶⁸Ga-FAPI PET/CT in Intrahepatic Tumors

Background: Gallium 68 (Ga-68)-labeled fibroblast activation protein inhibitor (FAPI) is of great diagnostic value for intrahepatic tumors. However, cirrhosis may lead to increased Ga-68-FAPI uptake in background liver, affecting the diagnostic ability of Ga-68-FAPI. Purpose: To assess the effect of cirrhosis on liver parenchyma and intrahepatic tumor uptake of Ga-68-FAPI and to compare the ability of Ga-68-FAPI and fluorine 18 (F-18)-labeled fluorodeoxyglucose (FDG) PET/CT to depict intrahepatic tumors in patients with cirrhosis. Materials and Methods: In this secondary analysis of a prospective trial, patients who underwent both Ga-68-FAPI and 18F-FDG PET/ CT and those who underwent only Ga-68-FAPI PET/CT between August 2020 and May 2022 were considered for inclusion in the cirrhotic or noncirrhotic group, respectively. Patients with cirrhosis were chosen via a comprehensive assessment of imaging and clinical data, and patients without cirrhosis were randomly selected. Ga-68-FAPI and F-18-FDG PET/CT data were measured by two radiologists. Between-groups and within-group data were tested with the Mann-Whitney U test and the Wilcoxon signed-rank test, respectively. Results: A total of 39 patients with cirrhosis (median age, 58 years [IQR, 50-68]; 29 male; 24 intrahepatic tumors) and 48 patients without cirrhosis (median age, 59 years [IQR, 51-67]; 30 male; 23 intrahepatic tumors) were evaluated. In patients without intrahepatic tumors, the liver Ga-68-FAPI average standardized uptake value (SUV avg) was higher in the cirrhotic group than in the noncirrhotic group (median SUV avg, 1.42 [IQR, 0.55-2.85] vs 0.45 [IQR, 0.41-0.72]; P =.002). However, no difference was observed in the diagnosis of intrahepatic tumor sensitivity (98% vs 93%, respectively). When compared with 18F-FDG, the sensitivity of Ga-68-FAPI PET/CT in the detection of intrahepatic tumors in patients with cirrhosis (41% vs 98%, respectively) and maximum standardized uptake value of tumors (median SUV max, 2.60 [IQR, 2.14-4.49] vs 6.68 [IQR, 4.65-10.08]; P <.001) were higher. Conclusion: The sensitivity of 68Ga-FAPI in the diagnosis of intrahepatic tumors was not affected by cirrhosis, and diagnostic accuracy of 68Ga-FAPI was higher than that of 18F-FDG in patients with cirrhosis.