Do People With Type 2 Diabetes Have a Higher Risk of Colon Cancer?

written by?Michael O?Leary

It was recently a good news, bad news week for people with type 2 diabetes. A study in Diabetes Care showed that people with diabetes are living longer. As reported by the New York Daily News, deaths from all causes among people with either type of diabetes dropped by 23 percent between 1997 and 2006. Most of the drop in deaths was attributed to better screening and treatments for cardiovascular disease.

On the same day at the Digestive Disease Week conference in San Diego researchers from Washington University in St. Louis found that among a sample of 125 people aged 40-49 with type 2 diabetes were diagnosed with colon cancer at twice the rate as a similar sample of same-aged people without diabetes.

As reported by WebMD, Dr. Susan Hongha Vu, a clinical gastroenterology fellow at Washington University presented the findings. She said that there have been a number of studies showing that people with type 2 diabetes have an increased risk of both precancerous lesions, called adenomas, and an increased risk of colon cancer. But as far as she could find in the scientific literature Vu told WebMD that no one had looked at whether people with type 2 diabetes should begin colon cancer screening sooner than is recommended for the general population.

To find out if screening earlier might advisable, Vu and colleagues looked at the medical records of 125 people aged 40-49 with type 2 diabetes, 125 records of the same age people without diabetes and the records of 125 people aged 50-59 without diabetes. All had a colonoscopy over a six-year period. What Vu?s team found was that among those 40-49 with type 2 diabetes, 30 percent had precancerous polyps, compared to 14 percent of those of the same age without diabetes. In the older non-diabetes group 32 percent had precancerous polyps.

The small study is far from conclusive and does not show that type 2 diabetes is a cause of colon cancer. Other factors may be contributing to the increased risk of cancer. Nevertheless, Vu said that one theory about why type 2 diabetes might be the culprit is that people with diabetes have abnormally high levels of insulin in their blood, which can spur the growth of cells, including precancerous and cancer cells.

Whether people with type 2 diabetes ought begin having colonoscopies in their 40?s will take much bigger studies to change the current guidelines. But Vu?s study is likely to spawn such studies that should answer this question. Until then, experts say it would not hurt for people with type 2 diabetes to consider having a colonoscopy, but the catch is the average $1800 cost is not likely to be covered by insurance until the guidelines are changed.

Until that happens, achieving the kind of reductions in mortality for colon cancer that have occurred as a result of cardiovascular monitoring will have to wait until these findings are studied in larger, randomized studies.

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