Jun 5 2007
The molecular imaging power of PET/CT is invaluable in noninvasively monitoring Crohn's disease, a chronic inflammatory disease of the gastrointestinal tract that mainly affects young people, according to a study released by Belgian scientists at the 54th Annual Meeting of SNM.
"Our study is the first one demonstrating the value of PET/CT in Crohn's disease," said Roland Hustinx, head of the nuclear medicine division at the University Hospital of Li'ge and professor of nuclear medicine at the University of Li'ge. "PET/CT (positron emission tomography/computed tomography) imaging,with the radiotracer fluorodeoxyglucose or FDG,could be used as a first-step test in patients with clinical or biological signs suggesting active disease," he noted. "PET/CT can answer the major question: What is the activity of the disease"" explained Hustinx.
Crohn's disease, an inflammatory bowel disease (IBD) that can affect the digestive system, has no medical cure, and its causes are unknown, explained Hustinx. Once the disease begins, it can fluctuate between periods of inactivity (remission) and activity (relapse). During relapses, symptoms,varying in nature, frequency and intensity,include abdominal pain, diarrhea and worsening general physical condition. Estimates indicate that up to 2 million people in this country could be affected by Crohn's and related diseases. IBD most commonly begins during adolescence and early adulthood.
"The clinical course of the disease is characterized by a succession of periods of clinical relapses and remissions," said Hustinx. "Its diagnosis relies on clinical and biological signs (markers of inflammation in the blood) as well as direct examination of the bowel using ileocolonoscopy, an endoscopic examination of the large bowel, where the last part of the small bowel (ileum) is also examined," added Hustinx, who indicated that prevalence of the disease is increasing.
"Endoscopic evaluation,a diagnostic medical procedure in which a small, flexible tube with a light and lens is inserted into the body to assess the interior surfaces of an organ,is the gold standard to answer, 'What is the activity of this disease"'" said Hustinx. The answer to this question will decide whether the clinician prescribes a treatment that is likely to be effective but also very costly and associated with side effects. "Ileocolonoscopy is invasive, unpleasant for the patient, sometimes incomplete due to unreachable segments and can only assess mucosal lesions, while the disease may sometimes affect deeper parts of the bowel wall," he indicated.
"The big advantage of PET/CT is that it is noninvasive, simple, fast and without any side effects. There was no preparation for the patients, except that they fasted for six hours. Each study took less than 20 minutes," said Hustinx. "If the PET/CT is positive, the doctor should confirm the results using endoscopy. If the PET/CT is negative, there would be no need for the endoscopy,given the high negative predictive value of the technique," he added.
"In our study, all bowel areas that showed severe endoscopic lesions were correctly identified by PET/CT. There was not a single case in which the ileocolonoscopy showed severe lesions and PET/CT showed a normal metabolic activity," said Hustinx. "Conversely, this means that when the PET/CT is negative,no matter how important the clinical symptoms are,the disease is not active," he added. "PET/CT has, therefore, the potential to deeply modify the exploration algorithm of patients with Crohn's, reducing the number of endoscopic examinations and allowing a better, noninvasive monitoring of the disease's activity," he indicated.
PET/CT molecular imaging,with radioactive drugs such as FDG,enables the collection of both biological and anatomical information during a single exam, with PET picking up metabolic signals of body cells and tissues and CT offering a detailed map of internal anatomy.
"Our results must be confirmed by other investigators on a larger scale," said Hustinx, indicating that his team is currently conducting a study evaluating the capacity of PET/CT to assess early on the response of the disease to "biological treatments." Treatment has been significantly improved over the past few years with the development of biological treatments, which have shown potential for obtaining mucosal healing in Crohn's disease, noted Hustinx. "This mucosal healing has been associated with higher sustained quality of life, lower rate of hospitalization and lower need for surgery. A sustained clinical remission,and a control of intestinal lesion,has become the target of new treatment strategies," he said.