Comparison of 68Ga-DOTA-FAPI and 18FDG PET/CT imaging modalities in the detection of liver metastases in patients with gastrointestinal system cancer

Purpose We aimed to compare the diagnostic performance of PET/CT imaging performed with 68Ga-DOTA-FAPI and 18FDG in detection of liver metastases in patients with gastrointestinal system (GIS) cancer. Methods A total of 31 patients who underwent 68Ga-DOTA-FAPI and 18F-FDG PET/CT examinations and diagnosed with GIS cancer (15 colorectal, 9 pancreas, 4 stomach and 3 other cancers) were included in the study. The presence of liver metastasis was decided based on histopathologic diagnosis, PET/CT, other radiologic examinations or tumor biomarker findings, and both PET/CT imaging findings were compared on the patient and lesion basis. Results Of the 31 patients, 28 were found as true positive with 68Ga-DOTA-FAPI-PET/CT and 17 with 18FDG-PET/CT. Of the 98 metastatic liver lesions determined according to our diagnostic criteria, 92 were found as true positive lesions with 68Ga-DOTA-FAPI-PET/CT and 65 with 18FDG-PET/CT. There was a statistically significant difference between both imaging modalities in the patient and lesion based comparisons (p < 0.05). When semiquantitative values (SUVmax, mlr) obtained from the lesions were compared between the two imaging methods, mlr values showed statistically significant difference in all tumor subgroups (p < 0.05). Conclusion It was concluded that 68Ga-DOTA-FAPI-PET/CT was superior over 18FDG-PET/CT in detection of liver metastases of GIS cancers and it can be a complementary method especially in negative cases with 18FDG-PET/CT.