High blood sugar raises risk of polyp recurrence

By Megan Rauscher

NEW YORK (Reuters Health) - People found to have elevated insulin or blood sugar levels at the time of colonoscopy to remove polyps face an increased risk of developing recurrent polyps, including advanced polyps -- the type with a high likelihood of progressing to cancer, research shows.

What's concerning is that the levels of blood sugar that produce this increased risk are actually not very high; they are "right at the border" of what doctors would consider "pre-diabetes," Dr. Andrew Flood of University of Minnesota, Minneapolis, noted in comments to Reuters Health.

For this reason, doctors and patients may want to consider more aggressive management of blood sugar than they might otherwise among people who have already had one or more polyps removed, Flood said.

He and colleagues measured fasting blood samples from 375 adults with and 375 without a recurrent polyp or "adenoma" following removal of one or more adenoma identified at a prior colonoscopy. They determined baseline insulin and blood sugar levels as well as changes in these levels over 4 years of follow-up in the Polyp Prevention Trial.

The investigators found that the likelihood of polyp recurrence was 56 percent higher among subjects with the highest insulin levels compared with those with the lowest levels. Similarly, the likelihood of polyp recurrence was 49 percent higher for subjects with the highest versus the lowest blood sugar levels.

"Even more importantly," Flood noted, high blood sugar was associated with a more than twofold increased risk of a recurrent advanced polyp.

Thus, he said, "even a modest elevation" of blood sugar into the range that represents an early stage in the progression from normal blood sugar control to insulin resistance and then to diabetes resulted in a large increase in risk of recurrence for polyps of the type that are most likely to progress to cancer.

These results "fit with the theory" that diabetes and even prediabetes can help fuel the development of colon cancer, the researchers note in their paper.

SOURCE: Gastroenterology, November 2007.