Use of PET-CT in the Management of Crohn's Disease

Crohn's disease (CD) is a gastrointestinal autoimmune disease thought to result from
exposure to luminal antigen. This exposure then results in a robust Th1 mediated immune
response which is not downregulated, resulting in intestinal tissue injury. Crohn's disease
most commonly involves the distal small intestine, a site that can be difficult to visualize
given its central location within the gastrointestinal tract.

A substantial proportion of patients do not respond to any of the standard therapies. Over
40% of patients do not respond to an initial anti-TNF (biologic) agent and approximately 10%
per year lose their response to these drugs. There is no standard definition of what
constitutes a patient who has primary biologic failure.

Disease activity is measured by indices such as the Crohn's Disease Activity Index (CDAI).
The CDAI includes a combination of clinical criteria and lab values. However, the CDAI is
limited by reliance on subjective criteria, limiting the score's use as a valid measure of
studying response to medical therapy. Clinically, reliance on CDAI can result in
inappropriate continuation of an ineffective therapy resulting in worsening of underlying
disease, and increasing risk of adverse reactions.

Small studies have demonstrated that PET scans may accurately quantify disease activity in
Crohn's. We propose to study CD patients with active flares to assess for a correlation
between PET activity and CDAI. Additionally, we will determine whether PET signal intensity
is predictive of clinical response to therapy with biologic agents.

The study proposes to test the hypothesis that PET can be used to determine which CD
patients with small bowel disease will be true responders (or nonresponders) to biologic
therapy at week 12. The use of PET to determine response to biologic therapy in small bowel
Crohn's disease would be novel.

Inclusion Criteria:

- Diagnosis of Crohn's disease

- CDAI1>220

- Identification of small bowel disease based on an imaging study (CT scan, Abdominal
ultrasound, MRI), colonoscopy, or histopathology 4. Need for initiation of biologic
therapy to control disease process.

Exclusion Criteria:

- Abdominal surgery within 8 wks of study entry

- Change in dose of steroids or immunomodulators within 2wks of study entry

- Pregnancy

- Active bacterial infection or undrained abscess

- Any contraindications to initiation of AntiTNF therapy (i.e. latent tuberculosis).