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Tests for colon cancer in colitis patients may lead to excessive treatment
Highly specific tests that find dysplasia in small areas might lead to unnecessary, quality-of-life worsening procedures-added 11/17/09
Ann Arbor - Screening for colon cancer in patients with chronic colitis has never been more sensitive.
But advanced screening methods, which can pick out pre-cancer years before a cancerous condition develops, are leading physicians to question the standard treatment options - which includes surgical removal of the entire colon, a procedure that can worsen a healthy patient's quality of life.
That's according to results of a study led by gastroenterologist Peter D.R. Higgins, M.D., Ph.D., M.Sc., assistant professor in the University of Michigan's Department of Internal Medicine. The study appears in the November edition of GUT.
"This finding raises the question of whether new, very sensitive detection methods may do more harm than good, and suggests that if we are finding very early pre-cancer, we may need to scale back our therapeutic intervention," says Higgins.
Patients with ulcerative colitis and Crohn's colitis, inflammatory bowel diseases that cause chronic inflammation of the digestive tract, are at increased risk of colon cancer, and the standard of care requires regular colonoscopy for surveillance every one to two years.
For these cases, the traditional screening method is to collect random biopsies throughout the colon via a colonoscope to look for the presence of pre-cancer (dysplasia) in colon cells.
Because the chance of hitting dysplastic cells in a random biopsy is quite low, when these pre-cancerous cells are found, it's because they have spread to form a large dysplastic field. Studies of people with colitis and pre-cancerous cells found by random biopsy have showed that they have a 20-40% chance of already having an invasive colon cancer, and the standard treatment is to surgically remove the colon.
But advanced endoscopic methods have made it possible for doctors to identify with much more sensitivity very early, small areas of pre-cancerous cells. The identification of these cells is not based on chance, and is not influenced by size or area. These cells are less likely to be associated with invasive cancer, and it may not be appropriate to surgically remove the colon if pre-cancerous cells are found with these sensitive methods.
Researchers in the study developed a mathematical model to determine the sensitivity of random biopsy surveillance and compare the detection threshold to that of an enhanced endoscopy.
The researchers calculated the confidence level with which dysplasia can be excluded, the dysplastic field size detection threshold, the predicted area of a dysplastic field, and the number of biopsies needed for a given dysplasia detection threshold and confidence level.
The results showed that if one out of 18 random biopsies contained pre-cancerous cells, this suggests a pre-cancerous area of 89 square centimeters (about 4 x 4 inches) is present. In contrast, advanced endoscopic methods can easily find areas of pre-cancerous cells that are only 1 centimeter across.
The researchers concluded that these much smaller, much earlier regions of pre-cancerous cells may not require removal of the colon. It is possible that less drastic methods, including removing small pre-cancerous areas through a colonoscope, may be sufficient. Additional study of the risk associated with these small pre-cancerous areas, and the best way to treat them, are needed.
Additional authors: Dahlia Awais, MD, MSc; Corey A. Siegel, MD, MHS.
Funding: Crohn's and Colitis Foundation of America, National Institutes of Health
Reference: Gut 2009; 58:1498-1503
Written by Margarita Bauza; phone: 734-764-2220
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