Comparative Analysis of 18 F-FAPI and 18 F-FDG PET/CT in Evaluation of Intestinal Lesions and Disease Activity in Ulcerative Colitis.

Abstract

Accurate evaluation of intestinal lesions and severity assessment of ulcerative colitis (UC) are crucial for therapeutic strategies and prognosis. This study aims to compare the efficacy of 18 F-FAPI and 18 F-FDG PET/CT in the evaluation of intestinal lesions and disease activity assessment of UC. This is a prospective cohort study, and patients with newly diagnosed or relapsed UC were enrolled. All participants underwent 18 F-FAPI PET/CT, 18 F-FDG PET/CT, abdominal contrast-enhanced CT, and colonoscopy within 1 week. Mayo Endoscopic Subscore (MES) was used as the reference standard for identification and severity assessment of intestinal lesions. Target-to-background ratio (TBR) of each segment in 18 F-FAPI/ 18 F-FDG PET/CT and global 18 F-FAPI/ 18 F-FDG PET/CT score were computed to represent the activity of independent segments and all segments, respectively. Before examinations, partial Mayo score was calculated based on clinical manifestations of patients, and levels of C-reactive protein, interleukin-6, erythrocyte sedimentation rate, platelet, and hemoglobin were determined. Finally, all data were analyzed to compare the efficacy of 18 F-FAPI and 18 F-FDG PET/CT in the evaluation of intestinal lesions and disease activity in UC. A total of 113 intestinal segments (including 90 lesion segments) were evaluated among 23 participants. Through receiver operating characteristic (ROC) analysis, 18 F-FAPI PET/CT showed significantly superior performance in detecting intestinal lesions compared with 18 F-FDG PET/CT ( P = 0.046) and abdominal contrast-enhanced CT ( P = 0.007). The correlations between FAPI-TBR and MES ( R2 = 0.75) and abdominal contrast-enhanced CT score ( R2 = 0.55) were stronger than those of FDG-TBR. 18 F-FAPI PET/CT showed superior discriminative capacity across different disease activity levels at both segmental ( P < 0.001) and patient-level ( P < 0.05) in intergroup comparison. The global 18 F-FAPI PET/CT score was significantly correlated with other activity indicators ( r = 0.49-0.76). Moreover, 18 F-FAPI PET/CT was also significantly superior to 18 F-FDG PET/CT ( P < 0.001) and abdominal contrast-enhanced CT ( P = 0.001) in detecting active lesions according to ROC analysis. The efficacy of 18 F-FAPI PET/CT in the evaluation of intestinal lesions and disease activity assessment of UC was superior to that of 18 F-FDG PET/CT. 18 F-FAPI PET/CT also correlated well with endoscopy, abdominal contrast-enhanced CT, clinical manifestations, and biomarkers. Therefore, 18 F-FAPI PET/CT may be a promising method for noninvasive assessment of disease activity of UC.