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

Background Gallium 68 (68Ga)-labeled fibroblast activation protein inhibitor (FAPI) is of great diagnostic value for intrahepatic tumors. However, cirrhosis may lead to increased 68Ga-FAPI uptake in background liver, affecting the diagnostic ability of 68Ga-FAPI. Purpose To assess the effect of cirrhosis on liver parenchyma and intrahepatic tumor uptake of 68Ga-FAPI and to compare the ability of 68Ga-FAPI and fluorine 18 (18F)-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 68Ga-FAPI and 18F-FDG PET/CT and those who underwent only 68Ga-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. 68Ga-FAPI and 18F-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 68Ga-FAPI average standardized uptake value (SUVavg) was higher in the cirrhotic group than in the noncirrhotic group (median SUVavg, 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 68Ga-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 SUVmax, 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. © RSNA, 2023 Supplemental material is available for this article.