A new study found an association between smoking and flat adenomas in the colon, perhaps explaining why smokers experience an earlier onset of colorectal cancers and why their cancers are detected at a more advanced stage compared with those of nonsmokers.1

Flat, nonpolypoid adenomas are more difficult to detect and are more aggressive than the typical polypoid (raised) adenomas detected in normal cancer screening. Because they are more aggressive, it is recommended that all such polyps be removed.

Although researchers do not know a great deal about risk factors associated with flat adenomas, smoking has been linked to colorectal neoplasia in several screening studies, according to the study's lead author, Joseph C. Anderson, MD, of the Carole and Ray Neag Comprehensive Cancer Center at the University of Connecticut in Farmington, Connecticut.

Because new-generation endoscopes use high-definition imaging, they can provide an extremely clear picture for endoscopists to better identify small polyps, early cancer, and flat lesions.

The prospective study looked at asymptomatic patients who were undergoing screening colonoscopies at Stony Brook University Medical Center in Stony Brook, New York, between November 2006 and October 2007. Researchers gathered a variety of demographic data, including cigarette use, number of packs per day, number of years patients had smoked, and the year of smoking cessation. These figures were used to calculate “pack years.” The categories ranged from “heavy smokers” to “still smoking or quit within the past 10 years” to “low-exposure smokers.”

Of the 600 patients, the median age was 56 years; 252 were men, and 348 were women. Of them, 127 patients were found to have 1 or more flat adenomas. Heavy smoking, age, and being male were statistically associated with flat adenomas of any size. Further, advanced flat adenomas were associated with heavy smoking, body mass index, sex, and red meat consumption. A multivariate analysis found that heavy smoking was the only variable to predict advanced flat colorectal neoplasia. Smoking also was a risk factor for patients who had flat adenomas greater than 6 mm in diameter and who did not have any polypoid adenomas.

The researchers say finding these adenomas may require special high-definition colonoscopies such as chromoendoscopy, because most of the flat adenomas were found on the right side of the colon. This technology involves spraying stains or dyes on the lining of the intestine during the endoscopic procedure to improve observation.


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    Anderson JC, Stein B, Kahi CJ, et al. Association of smoking and flat adenomas: results from an asymptomatic population screened with a high-definition colonoscope. Gastrointest Endosc.. 2010; 71: 1234-1240.