The potential role of FDG PET-CT in the characterization of the activity of Crohn's disease, staging follow-up and prognosis estimation: a pilot study.

Objectives: FDG PET-CT is a global, noninvasive, sensitive method to determine the location and activity of inflammatory lesions. Segmental FDG uptake is proportional with immune cell infiltration of bowel. Our aim was to evaluate prospectively the role of PET in patients with active Crohn's disease (CD) before and after one year's biological therapy, and to compare simple endoscopic score for CD (SES-CD), CD activity index (CDAI) and global PET scores. We also analyzed the prognostic value of initial PET scores.

Patients: Twelve patients were selected: six male/six female, ages between 18 and 39, average: 24 years, with CDAI values >300.

Methods: We scored the FDG uptake in the small intestine and the four colon segments (on a scale 0-3 for each), and summed them thus forming a global PET score. The scoring was based on the maximal standardized uptake value of the intestinal segment, related to the SUVmax of the liver (as a reference for normal tissue activity). The SES-CD, CDAI and global PET scores before and after treatment were statistically compared.

Results: There were significant changes in CDAI and SES-CD after therapy, PET scores improved only in patients' subgroup with high (>4) initial PET score, indicating good prognosis of biological treatment. In active disease, PET was more informative than endoscopy to access the extent of the inflammation, and small intestine involvement.

Conclusions: FDG PET-CT score is a promising, noninvasive complementary method in the staging, treatment planning and follow-up of CD. Limitation of the study is the small number of patients.