The Study and the Results: In this week’s Journal of the American Medical Association (JAMA, March 5, 2008; 299(9): 1027-1035), an article by Roy Soetikno et al. showed that flat colon polyps, which are quite difficult to visualize compared to the mushroom-shaped or polypoid variety, are nevertheless quite common, being found in a bit over 9% of 1819 male patients over age 60 who underwent colonoscopy at a Veterans Administration hospital in California. The polypoid variety were found in about 37% of the patients. More important, the flat polyps [see the graphic from the JAMA article, Types of colon polyps] accounted for about half of all the early malignancies (carcinoma in situ and invasive cancer) even though, again, such malignancies were uncommon, a total of just 28 cases (1.5%). Additionally, the investigators found 13 advanced cancers, bringing the cancer total to 51 cases (2.8%) overall, or about 1 out of 40 patients who were screened.
What Does This Mean?: The apparent importance of flat polyps as producing half of all early malignancies is an eye-opener. A number of issues immediately present themselves. First, how hard is it to find these flat polyps? Special techniques were used to visualize them. Do all our endoscopy colleagues know and use these techniques? I shall be asking. Second, if you had a colonoscopy and such special techniques were not used (such as the indigo carmine dye solution), was your colonoscopy sufficiently reliable? Should we shorten the follow-up interval regardless of what was said at the time of that study? Again, I shall be asking. Third, what is the place of CT colonography with this new information? If half of the dangerous early lesions are flat and probably invisible to current CT colonography technology, should we use that at all? I have been strongly supportive of CT colonography as an alternative to optical colonoscopy, with the previous understanding that early polyps were actually polypoid and therefore visible to the X-ray technique providing they were 5-6 mm or bigger. If this is really not the case, then CT colonography is not truly a close-to-equal alternative to optical colonoscopy. I have already contacted my CT colonography experts at BIDMC and MGH and begun an exchange on this issue.
In Sum: The body is more complex than we know. Flat polyps in the colon may be equally the cause of colon cancers as the more obvious polypoid variety, but they are much harder to detect. In fact, detection of such polyps requires an added level of attentiveness and different techniques for the physician doing colonoscopies, and the X-ray procedure of CT colonography is not obviously up to the task of finding such polyps. As a consequence, I will be recommending optical colonoscopies for all of us over 50 at the recommended intervals in preference to the X-ray studies, and will be opening a dialog with the physicians I refer to for optical colonoscopy to be sure each one is knowledgeable about the special visualization techniques required to find these sneaky flat lesions.