Diabetes Raises Colon Cancer Risk

doctor looking at chartPeople with diabetes — long known to be at higher risk for heart disease,
kidney failure and eye and foot trouble — now have one more thing to be
concerned about: A new study finds they are also more vulnerable to colon

“Diabetics are 1.4 times more likely to have been told they have colon
cancer,” said Dr. Donald Garrow, a clinical instructor and a masters in clinical
research fellow at the Medical University of South Carolina, Charleston.

Garrow said other studies have found the same association, but he believes
his study is the largest cross-sectional survey to evaluate the question of
whether diabetics face a higher colorectal cancer risk.

Garrow was to present the findings Tuesday at the annual scientific meeting
of the American College of Gastroenterology, in Honolulu.

His team based its findings on data involving more than 226,000 Americans,
collected from 1997 to 2003 as part of the National Health Interview Survey.

A total of 5.9 percent of respondents had a history of diabetes. Even after
compensating for other factors that affect risk — age, gender, alcohol use,
tobacco use and exercise — the researchers found that individuals with diabetes
were more likely than non-diabetics to develop colon cancer.

Exactly why that might be isn’t certain, Garrow said, but he noted that
elevated insulin levels in the blood of those with diabetes are thought to
affect cells in the colon’s mucosal lining.

“In the lab, these mucosal cells, when exposed to high levels of insulin,
develop into cancer cells,” he said. “There are insulin-like receptors on the
colon’s mucosal cells. The insulin seems to attach itself to the mucosal cells
and cause changes that become cancer.”

Most diabetics surveyed in the study had obesity-linked type 2 diabetes, in
which the body becomes insensitive to insulin. A minority had the inherited type
1 form of diabetes, which results from the body’s failure to produce insulin,
the hormone that helps glucose enter cells of the body and supply them with

An estimated 14.6 million people in the United States have been diagnosed
with diabetes, according to the American Diabetes Association. More than 145,000
new cases of colorectal cancer are expected to be diagnosed in the United States
this year, according to the American Cancer Society, and over 56,000 patients
will die from the disease.

Garrow said the study highlights the fact that diabetics must be especially
careful to follow colorectal cancer screening guidelines. The American Cancer
Society now recommends that, beginning at age 50, men and women at average risk
should be screened with tests such as the fecal occult blood test, invasive
exams such as sigmoidoscopy and colonoscopy, and/or double barium enema.

Another expert, Dr. Kevin Adgent, said the research will inspire him to “look
at my diabetic patients more closely.”

Adgent, an internal medicine physician in Wilmington, N.C., said he treats
many patients with diabetes. Praising the study’s large sample size, he said the
finding “makes me more aware of getting my diabetic patients screened

More information

To learn more about diabetes, visit the American Diabetes

SOURCES: Donald Garrow, M.D., clinical instructor, masters in
clinical research fellow, Medical University of South Carolina, Charleston;
Kevin Adgent, M.D., physician, Wilmington, N.C.; Nov. 1, 2005, presentation,
American College of Gastroenterology 70th annual scientific meeting, Honolulu

Last Updated: Nov. 1, 2005

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