Type 2 diabetes ups risk for colon polyps, cancer

Type 2 or non-insulin dependent diabetes is associated with increased risk of developing colorectal cancer, particularly among men, according to a study reported in the American Journal of Gastroenterology.

Many studies that have examined the connection between diabetes and colorectal cancer have yielded contradictory results, Dr. Paul J. Limburg and his research team note, and they attribute this to shortcomings in the studies.

To avoid these pitfalls, Limburg, from Mayo Clinic College of Medicine in Rochester, Minnesota, and his group evaluated data from the Rochester Epidemiology Project, which has medical information for close to 86,000 residents. They analyzed the relationship between a diagnosis of type 2 diabetes between 1970 ann 1994 and the subsequent occurrence rate of colorectal cancer through 1999.

There were 1,975 residents with diabetes and 51 cases of colorectal cancer.

After accounting for age and calendar period, the standardized incidence ratio (SIR) - the ratio of the observed to the expected number new cases of cancer - was 1.39, or 39% higher than expected among people with diabetes. However, the association was statistically significant only among men, for whom the SIR was 1.67.

The risk of colorectal cancer was significantly higher for diabetics who were current or former smokers, so the researchers think that men's higher propensity to smoke may have influenced the difference in risk.

"Colorectal cancer screening ... and tobacco cessation should be strongly emphasized for type 2 diabetes patients," Limburg and his associates advise.

SOURCE: American Journal of Gastroenterology, August 2006.