Last Modified: April 27, 2008
Dear OncoLink "Ask The Experts,"
Can you please comment on new techniques to identify flat growths on colon wall when under going colonoscopy screening procedure?
Timothy C. Hoops, MD, Clinical Professor of Medicine and Director of GI, Penn Presbyterian Medical Center, responds:
A recent article regarding flat polyps has raised a lot of interest about the existence of these lesions. Obviously, patients are concerned that polyps which are at high risk for developing cancers are potentially missed during screening. This is an issue that has been discussed for some time, and there is suspicion as to the number of these polyps that exist in the US population, which the recent study tried to quantify. I would say that the results are somewhat surprising in terms of the frequency with which flat polyps were found. It may be an issue of differences in the classification of these polyps. Some of the differences may be due to varying technique and more vs. less careful evaluation, which may identify greater or fewer of these polyps. New endoscopic technologies with different types of light sources may allow better visualization, although that is unclear at this time. Some have promoted the use of special dyes to enhance visualization, and the recent study employed some of these newer techniques.
All of these techniques make the procedure more time-consuming and demanding. Obviously, the colonoscopist needs to be very careful during the evaluation of the colon, and this is consistent with previous studies which found that the slower the endoscope withdrawal, the greater the number of polyps found. The good news is that, with many years of experience, the number of colon cancers found after colonoscopy is actually quite small, and supports the concept of reduction of colon cancer risk by colonoscopy. This would suggest that we, as a profession, are not missing a large number of these polyps. Again, the most important factor is that the endoscopist conscientiously tries to carefully evaluate the entire colon. With such an exam, the risk for future colon cancers is markedly reduced.