FRIDAY, June 11 (HealthDay News) -- A new study has uncovered a strong link between smoking and the development of precancerous polyps called flat adenomas in the large intestine, a finding that researchers say may explain the earlier onset of colorectal cancer among smokers.

Flat adenomas are more aggressive and harder to spot than the raised polyps that are typically detectable during standard colorectal screenings, the authors noted. This fact, coupled with their association with smoking, could also explain why colorectal cancer is usually caught at a more advanced stage and at a younger age among smokers than nonsmokers.

"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," study author Dr. Joseph C. Anderson, of the Neag Comprehensive Cancer Center at the University of Connecticut Health Center, said in a news release from the American Society for Gastrointestinal Endoscopy.

But, "smoking has been shown to be an important risk factor for colorectal neoplasia [tumor formation] in several screening studies," he said.

Anderson and his team report their findings in the June issue of GIE: Gastrointestinal Endoscopy.

Most colorectal cancers are thought to begin as a small colorectal polyp, the researchers noted. Therefore, polyp removal is believed to be critical to prevent disease.

To explore the potential for a connection between smoking and the risk for developing the flat polyps, the research team tracked 600 patients -- average age 56 -- who underwent a colonoscopy screening at Stony Brook University Medical Center in New York without previously displaying any symptoms for colorectal cancer.

Patients were asked to provide a wide range of demographic information, including smoking history. A little more than half were deemed nonsmokers, while 115 were considered heavy smokers and 172 were considered light smokers.

In addition to being older and male, being a heavy smoker was linked to having flat adenomas of any size, the researchers found. Heavy smoking was also found to be linked to having advanced-stage flat polyps.

The authors concluded that smoking is a strong risk factor for developing flat colorectal adenomas in general, and for having particularly large adenomas.

An accompanying editorial suggests the data be used by doctors to counsel patients about the risks of smoking and the need for colorectal cancer screening among smokers.

More information

For more on colon cancer, visit the National Institutes of Health.