18F-FAPI-42 PET/CT enhances the diagnostic efficacy for peritoneal metastasis of colorectal cancer and guides treatment decisions: an original retrospective study

Colorectal cancer is the third-most common type of cancer. When peritoneal metastasis (PM) develops, diagnosing metastatic lesions is difficult and the prognosis is poor. This study aimed to compare the value of fluorine-18 fibroblast activation protein-specific inhibitor (18F-FAPI-42) and fluorine-18 fluorodeoxyglucose (18F-FDG) positron emission tomography/computed tomography (PET/CT) for detecting PM of colorectal cancer and to guide clinical decision-making.BackgroundColorectal cancer is the third-most common type of cancer. When peritoneal metastasis (PM) develops, diagnosing metastatic lesions is difficult and the prognosis is poor. This study aimed to compare the value of fluorine-18 fibroblast activation protein-specific inhibitor (18F-FAPI-42) and fluorine-18 fluorodeoxyglucose (18F-FDG) positron emission tomography/computed tomography (PET/CT) for detecting PM of colorectal cancer and to guide clinical decision-making.Forty-eight patients with PM who underwent both 18F-FAPI-42 and 18F-FDG PET/CT examinations were studied. The maximum standardized uptake value (SUV max), tumor-to-background ratios (TBRs) and peritoneal cancer index (PCI) of the PM were compared between the two imaging techniques. The intraclass correlation coefficient (ICC) was used to compare the consistency between the PET/CT PCI score and the intraoperative PCI. A receiver-operating characteristic curve was used to predict the accuracy of CC-0 cytoreduction (complete cytoreduction with no visible disease).MethodsForty-eight patients with PM who underwent both 18F-FAPI-42 and 18F-FDG PET/CT examinations were studied. The maximum standardized uptake value (SUV max), tumor-to-background ratios (TBRs) and peritoneal cancer index (PCI) of the PM were compared between the two imaging techniques. The intraclass correlation coefficient (ICC) was used to compare the consistency between the PET/CT PCI score and the intraoperative PCI. A receiver-operating characteristic curve was used to predict the accuracy of CC-0 cytoreduction (complete cytoreduction with no visible disease).The sensitivity and accuracy of 18F-FAPI-42 PET/CT for detecting PM were higher than those of 18F-FDG PET/CT (82.1% vs 61.1%, P