Elboga_2022_Mol.Imaging.Biol_24_789

PURPOSE: In this study, we aimed to investigate the utilization of (68)Ga-FAPI PET/CT in comparison to (18)FDG PET/CT to evaluate the peritoneal involvement of the gastrointestinal malignancies alongside primary lesions and other metastatic foci. PROCEDURES: A total of 37 patients with various gastrointestinal malignancies with accompanying peritoneal involvement who underwent (68)Ga-FAPI PET/CT and (18)FDG PET/CT imaging between September 2020 and June 2021 were included in this retrospective study. SUV(max) values of (68)Ga-FAPI and (18)FDG were compared according to lesion locations. Also, the lesion localization ability of both imaging was compared in patient basis. RESULTS: 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(max) value of peritoneal metastases (p < 0.001) was significantly higher with (68)Ga-FAPI PET/CT compared to that with (18)FDG PET/CT, as in primary lesions (p < 0.001), lymph node metastases (p = 0.006), liver metastases (p = 0.002), and bone metastases (p = 0.018). A total of 185 lesions was detected in the initial assessment with (18)FDG PET/CT. Of the total lesions detected with (18)FDG PET/CT, 5 of them were evaluated as benign lesions with (68)Ga-FAPI PET/CT also in accordance with the reference standard. In addition to 180 lesions detected with (18)FDG PET/CT, a total of 37 additional malignant lesions, 12 of which were peritoneal metastases, were detected with (68)Ga-FAPI PET/CT. CONCLUSION: (68)Ga-FAPI PET/CT was determined to be superior to (18)FDG PET/CT in terms of detection of peritoneal involvement with high image quality as well as primary tumor and other metastatic foci. Consequently, (68)Ga-FAPI PET/CT can be used as a complementary imaging modality especially for inconclusive (18)FDG findings due to the lack of accuracy of (18)FDG PET/CT in some of the metastatic regions, especially in the liver.