Some tumors seem affected by tobacco use

New research suggests a link between cigarettes and a colon cancer, a disease usually not associated with smoking.

Colon cancer patients whose tumors had unstable DNA, and thus were called microsatellite instability (MSI) tumors, were more likely to be smokers than those whose tumors did not have MSI, says a University of Utah study.

"This helps our understanding of the disease," says Marty Slattery, a professor of epidemiology at Utah. "It provides support for the idea that lifestyle factors can cause tumor mutations."

However, the study does not conclude that smoking causes colon cancer, says Monica Alvarado, a cancer genetic counselor at the University of Southern California's (USC) Norris Comprehensive Cancer Center.

"The study was not comparing smokers and nonsmokers and seeing if smokers had more colon cancer," she says.

Rather, the researchers wanted to determine whether lifestyle factors like smoking, physical activity and use of aspirin contributed to MSI tumors. Although some MSI tumors are associated with a genetic mutation, most are not.

What they found was a particularly strong link between tobacco use and MSI among people who had started smoking at a young age, smoked for at least 35 years and either smoked currently or had stopped 15 years before their disease was diagnosed, the study says. Findings appear in the Nov. 15 Journal of the National Cancer Institute.

The study found no links with other lifestyle factors.

Smoking has been linked to other cancers, such as bladder and pancreatic, but the relationship between smoking and colon cancer has been greatly debated.

Studies consistently have found an association between cigarette smoking and adenomas, the precursor lesions in most cases of colon cancer. But an editorial published with the Utah study contends that research supporting a link between smoking and colorectal cancer has been inconsistent.

(From HealthScout)