Highly specific tests that find dysplasia in small areas might lead to unnecessary and quality-of-life worsening procedures for patients with chronic colitis, a study by researchers at the University of Michigan has found.
"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," lead author Peter D.R. Higgins, MD, PhD, MSc, a gastroenterologist in the Department of Internal Medicine, said in a news release about the study, published in the November issue of Gut.
Patients with ulcerative colitis and Crohn's colitis are known to be 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 has been to collect random biopsies throughout the colon via a colonoscope to look for the presence of dysplasia in colon cells.
Because the chance of hitting dysplastic cells in a random biopsy is low, when these pre-cancerous cells are found, it is unfortunately usually because they have spread to form a large dysplastic field. Studies of people with colitis and pre-cancerous cells found by random biopsy have shown that such patients have a 20% to 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 to identify with much more sensitivity very early, small areas of dysplasia. The identification of these cells, therefore, 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.
Dr. Higgins, along with co-researchers Dahlia Awais, MD, MSc, and Corey A. Siegel, MD, MHS, developed a mathematical model to determine the sensitivity of random biopsy surveillance and compare the detection threshold with that of an enhanced endoscopy.
They 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 dysplasia it suggests that a pre-cancerous area of 89 square centimeters is present. In contrast, advanced endoscopic methods can easily find areas of pre-cancerous cells that are as small as one centimeter across.
The researchers concluded that these much smaller, much earlier regions of dysplasia 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, they said, noting that additional study of the risk associated with these small pre-cancerous areas, and the best way to treat them, are needed.
The study was supported with funding from the Crohn's and Colitis Foundation of America and the NIH.