SMOKING LINKED TO FLAT ADENOMAS

June 18, 2010 — Because smoking is associated with flat adenomas, smokers may require screening with high-definition colonoscopes to detect flat adenomas, according to the results of a prospective cross-sectional study reported in the issue of Gastrointestinal Endoscopy.

"Little is known regarding the risk factors for these flat lesions, which may account for over one-half of all adenomas detected with a high-definition colonoscope," said lead author Joseph C. Anderson, MD, from Neag Comprehensive Cancer Center, University of Connecticut Health Center in Farmington, in a news release. "Smoking has been shown to be an important risk factor for colorectal neoplasia in several screening studies. The aim of this study was to investigate smoking as a risk factor for flat adenomas in an average risk population undergoing screening colonoscopy."

At a university hospital endoscopy center, 600 asymptomatic patients presenting for colorectal cancer (CRC) screening were screened with a high-definition (1080i signal) wide-angle (170° field of view) colonoscope. Participants also provided information regarding demographic factors, diabetes and other medical conditions, medications, family history of CRC, diet, and smoking history. The primary endpoint was polyp morphology evaluated according to the Japanese Research Society Classification criteria.

After multivariate analysis, smoking (heavy smokers vs nonsmokers) was associated with flat adenoma of any size (adjusted odds ratio [OR], 2.53; 95% CI, 1.60 - 4.00), with flat adenoma 6 mm in diameter or greater (adjusted OR, 3.84; 95% CI, 2.02 - 7.32), and with flat advanced adenomas (adjusted OR, 2.81; 95% CI, 1.08 - 7.30).

"Smoking was associated with flat adenomas in our population," the study authors write. "Our findings may explain the earlier onset of CRC in smokers as well as the advanced stage with which they present, with compared with nonsmokers. Smokers may require screening with high-definition colonoscopes to detect flat adenomas."

Limitations of this study include cross-sectional design, predominantly young population, possible unmeasured confounders, and lack of data on smoking status when flat adenomas first developed.

In an accompanying editorial, Dayna Early, MD, from Washington University School of Medicine in St. Louis, Missouri, notes that flat lesions are more difficult to identify than polypoid lesions but that data to support use of advanced imaging in smokers are not available from this study.

"Ongoing emphasis should be placed on high-quality screening examinations and good bowel preparation because these are critical in detecting right-sided lesions," Dr. Early said. "Finally, we should be on the lookout for flat adenomas not only in smokers, but in all patients undergoing screening colonoscopy and use the best technology available to us to do so."

The Stony Brook University General Clinical Research Center supported this study. The study authors and Dr. Early have disclosed no relevant financial relationships.

Gastrointest Endosc. 2010;71:1234-1240, 1241-1243.