Collagen-binding probe PET/MR for distinguishing fibrotic from inflammatory strictures in Crohn's disease.

Abstract

To evaluate the feasibility and diagnostic performance of ⁶⁸Ga-CBP8 PET/MR enterography for noninvasive detection of bowel collagen deposition and differentiation of inflammatory from fibrotic or mixed strictures in Crohn's disease. Patients with stricturing Crohn's disease scheduled for bowel resection or endoscopic biopsy were prospectively enrolled. PET/MR enterography was performed after intravenous administration of ⁶⁸Ga-collagen binding probe 8 (⁶⁸Ga-CBP8). Focal radiotracer uptake was defined as activity exceeding local background and anatomically corresponding to an MR-identified bowel stricture. Surgical and biopsy specimens underwent blinded pathologic evaluation for fibrosis. Descriptive statistics, sensitivity and specificity were calculated to assess diagnostic performance. Differences in SUVmax and SUVmax stricture-to-uninvolved bowel ratio between fibrotic and non-fibrotic segments were evaluated using the Mann-Whitney U test, with p < 0.05 considered statistically significant. Five patients (4 M, 1 F; median age: 50; IQR: 11) with seven strictured bowel segments (median length: 24 mm; IQR: 14) were included. Five segments (71.4%) demonstrated focal ⁶⁸Ga-CBP8 uptake and were pathologically confirmed as mixed inflammatory-fibrotic strictures. Two segments (28.6%) showed no significant uptake and were confirmed as strictures devoid of fibrosis. ⁶⁸Ga-CBP8 PET/MR enterography achieved 100% sensitivity for mixed inflammatory-fibrotic strictures and 100% specificity for non-fibrotic strictures. SUVmax and SUVmax stricture-to-uninvolved bowel ratio were higher in fibrotic than non-fibrotic segments (median SUVmax: 2.29 vs. 1.01; median ratio: 2.36 vs. 0.88), although without statistically significant differences (both p = 0.095). ⁶⁸Ga-CBP8 PET/MR enterography is a feasible noninvasive technique to assess bowel strictures in Crohn's disease and may enable differentiation of inflammatory and fibrotic components. ClinicalTrials.gov, NCT06252493. Date of first enrollment: 19 December 2023. Registered: 2 February 2024 (retrospectively registered).