Comparison of 68 Ga-FAPI PET/CT and 18 FDG PET/CT Modalities in Gastrointestinal System Malignancies with Peritoneal Involvement

In this study, we aimed to investigate the utilization of Ga-FAPI PET/CT in comparison to FDG PET/CT to evaluate the peritoneal involvement of the gastrointestinal malignancies alongside primary lesions and other metastatic foci. A total of 37 patients with various gastrointestinal malignancies with accompanying peritoneal involvement who underwent Ga-FAPI PET/CT and FDG PET/CT imaging between September 2020 and June 2021 were included in this retrospective study. SUV values of Ga-FAPI and FDG were compared according to lesion locations. Also, the lesion localization ability of both imaging was compared in patient basis. Of the 37 patients with peritoneal involvement (23 males and 14 females; median age, 62.8 ± 12.7 years), 35.1% (n = 13) had colorectal cancer, 37.8% (n = 14) gastric cancer, and 27.0% (n = 10) pancreaticobiliary cancer. While 45.9% of them were operated, the remaining did not have surgery. The mean time interval between two studies was 3.2 days (range: 2-6 days). The mean SUV value of peritoneal metastases (p