FDG PET and PET/CT in Crohn’s disease

Abstract

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Objectives: Patients with the “Stenotic/Stricturing” phenotype of Crohn’s disease (CD) often present with obstructive symptoms. While surgery is indicated in patients with fibrotic strictures, medical therapy may be beneficial in those with active inflammation. Our objective was to evaluate the use of FDG PET and PET/CT as a non-invasive test in the pre-surgical management of patients with known CD and obstructive symptoms.

Methods: 17 patients with known CD and obstructive symptoms were prospectively evaluated prior to surgery with FDG PET/CT (Discovery LS, GE Healthcare). Patients received oral water contrast, and all had non-contrast CT scans, which were used for attenuation correction. 8 patients also had IV contrast CT scans. Image interpretation was by consensus of 2 readers with knowledge of patient participation in the study but no other clinical history. Images were interpreted in the following order: PET alone; PET/CT, PET/IV-contrast CT (n=8). Lesions were graded on a 5-point scale for certainty of the presence of active inflammation (0 = definitely normal; 1 = probably normal; 2 = equivocal; 3 = probably abnormal; and 4 = definitely abnormal) and on a 3-point scale for localization (0 = unknown; 1 = probable; and 2 = definite). Pathology is currently available for 6 patients; median time from PET/CT to surgery was 25 days (range 2-148).

Results: On PET alone, 13/17 patients had active inflammation, 1 had equivocal findings, and 3 had no active inflammation. On PET/CT, 14 had inflammation, 2 were equivocal, 1 did not have active inflammation. In 6 patients with pathologic correlation, PET was true positive in 3, false negative in 1, and false positive in 2. FDG PET/CT was true positive in 4 and false positive in 2. SULmax tended to be higher in active inflammation vs fibrosis (8.4 ± 2.2 vs 5.6 ± 1.8, p=0.06, one-tailed t test). For 28 lesions visualized on both PET and PET/CT, PET/CT decreased the number of uncertain diagnostic findings by 58%, particularly by allowing visualization of abnormal bowel wall thickening, and improved lesion localization by 90%. IV contrast CT increased diagnostic certainty for only 3 lesions.

Conclusions: FDG PET/CT is a promising non-invasive tool for distinguishing active inflammation versus fibrosis prior to surgery in patients with known CD. Further evaluation in a larger patient series with normal controls will be of interest.

Research Support (if any): The Broad Medical Research Program, Grant BMRP IBD-0122R