Imaging fibroblast activation protein in liver cancer. A single-center post hoc retrospective analysis to compare [${}^{68}$Ga]Ga-FAPI-04 PET/CT versus MRI and [${}^{18}$F]-FDG PET/CT

This study aimed to evaluate the potential utility of [${}^{68}$Ga]Ga-FAPI-04 PET/CT for diagnosing primary and metastatic lesions in patients with liver cancer, as well as to compare it with contrast-enhanced CT (CE-CT), liver MRI, and [${}^{18}$F]-FDG PET/CT. We performed a single-center post hoc retrospective analysis of data obtained from a prospective parent study (NCT04416165). This study included 34 patients diagnosed with or suspected hepatic lesions who underwent concomitant [${}^{68}$Ga]Ga-FAPI-04 and [${}^{18}$F]-FDG/CT scans. Moreover, these patients underwent liver MRI (n = 34) and CE-CT (n = 25). Histopathologic (n = 62) or radiographic follow-up (n = 128) served as the reference standard for the final diagnosis. Among the 34 patients, 20, 12, and 2 patients presented with hepatocellular carcinomas, intrahepatic cholangiocarcinomas, and benign hepatic nodules, respectively. The sensitivities of CE-CT, MRI, [${}^{68}$Ga]Ga-FAPI-04, and [${}^{18}$F]-FDG/CT for detecting primary liver tumors were 96%, 100%, 96%, and 65%, respectively. Regarding the diagnosis of all intrahepatic lesions, the per-lesion detection rate of [${}^{68}$Ga]Ga-FAPI-04 PET/CT was slightly lower than that of MRI (85% vs. 100%, P = 0.34) and significantly higher than that of [${}^{18}$F]-FDG PET/CT (85% vs. 52%, P < 0.001). Regarding the diagnosis of all malignant lesions (including extrahepatic disease), the tumor detection rate of [${}^{68}$Ga]Ga-FAPI-04 PET/CT was 87.4%, which was significantly higher than that of [${}^{18}$F]-FDG PET/CT (65.0%, P < 0.001). Our findings indicate that the sensitivity of [${}^{68}$Ga]Ga-FAPI-04 PET/CT to correctly identify primary liver tumors and metastatic lesions is equivalent to that of CE-CT and liver MRI. Moreover, [${}^{68}$Ga]Ga-FAPI-04 PET/CT is better at identifying liver lesions than [${}^{18}$F]-FDG PET/CT, and its use may improve tumor staging, recurrence detection, and implementation of necessary treatment modifications.