Purpose: Lesions with a high uptake of 18F-fluorodeoxyglucose (18F-FDG) on positron emission tomography-computed tomography (PET-CT) can be benign and malignant. New radiotracers, such as the gallium 68 (68Ga)-labeled fibroblast activation protein inhibitor 4 (FAPI-04), could be used to diagnose colorectal carcinoma. This study aimed to evaluate the efficacy of 68Ga-FAPI-04 PET in differentiating benign from malignant 18F-FDG-avid colorectal lesions.
Methods and materials: An azoxymethane/dextran sodium sulfate (AOM/DSS)-induced rat colorectal tumor model was developed. Double-tracer 68Ga-FAPI-04 and 18F-FDG PET-CT were applied in the rat model and 22 patients. The PET-CT data were analyzed with enteroscopy, histopathologic observations, immunohistochemistry (IHC) staining, and radioautography results. One hundred seventy-two patients with pathologically confirmed colorectal lesions were enrolled in FAP IHC staining.
Results: We found that 68Ga-FAPI-04 PET-CT imaging accurately distinguished the malignant from benign inflammatory lesions in an AOM/DSS-induced rat colorectal tumor model. Of 22 patients with gastric cancer but without colorectal carcinoma, 8 had 18F-FDG uptake in the colorectum, but 68Ga-FAPI-04 PET was negative in these sites. An inflammatory lesion or adenoma did not interfere with 68Ga-FAPI-04 PET imaging. Among the 18F-FDG-avid colorectal lesions, 80 of 94 pathologically malignant lesions (85.1%) were FAP-positive, and only 16 of the 78 premalignant or benign lesions (20.5%) had a weak 68Ga-FAPI-04 uptake.
Conclusions: 68Ga-FAPI-04 PET-CT could be used to distinguish between benign and malignant 18F-FDG-avid colorectal lesions.
Copyright © 2023 The Author(s). Published by Elsevier Inc. All rights reserved.