As reported by Reuters Health, May 10, 2010.

Heavy Smokers Have More Flat Adenomas on Colorectal Screening

By Dave Levitan

NEW YORK (Reuters Health) - The aggressive type of polyp known as a flat adenoma is associated with smoking, which might help explain earlier onset of colorectal cancer in smokers, a prospective cross-sectional study suggests.

Flat adenomas are a distinct class of polyp that are thinner than other lesions.

"They may be difficult to detect and may be the reason why there are 'missed cancers,'" said lead study author Dr. Joseph Anderson, of the University of Connecticut Health Center in Farmington. "Identifying risk factors can aid in determining which patients require special imaging techniques to detect the flat polyps."

Dr. Anderson and his colleagues have found that smoking status is one of those risk factors. They enrolled 600 asymptomatic patients undergoing colorectal cancer screening, including 313 non-smokers, 115 heavy smokers, and 172 low-exposure smokers.

The results were published online April 26 in Gastrointestinal Endoscopy.

Being a heavy smoker was associated with a higher risk of having a flat adenoma (OR 2.53) in a multivariate analysis. Age and male gender also were significant risk factors for flat adenomas.

Heavy smoking also was associated with having only flat adenomas of at least 6 mm in size, and it was the only factor on multivariate analysis associated with having an advanced flat colorectal neoplasia.

The authors say these data are clinically relevant because of the special high-definition colonoscopes that may be needed to detect flat adenomas.

Dr. Anderson told Reuters Health that this is a promising start but there's still a need for more research into flat adenomas. "We need to see if smokers are at risk for the interval cancers, those cancers that arise in between screening."

He added, "Most flat lesions are on the right side of the colon and there is much data now to suggest that the interval cancers are on the right side. Perhaps the flat adenomas account for many of these lesions."