The findings suggest that hyperinsulinemia underlies the association. In previous studies diabetes has been consistently linked to cancers of the pancreas, liver, endometrium, and colon/rectum, the researchers note. By contrast, the association with other malignancies, such as esophagus, stomach, or breast cancer, is less consistent, possibly because the studies have involved small sample sizes.

To address this issue, Dr. Sun Ha Jee, from Yonsei University in Seoul, and colleagues conducted a 10-year prospective study involving more than 1 million Koreans between the ages of 30 and 95 years who had a biennial medical evaluation between 1992 and 1995. The researchers' findings appear in the January 12th issue of the Journal of the American Medical Association.
During follow-up, men and women with fasting glucose levels of at least 140 mg/dL were about 25% more likely to die from cancer than those with levels less than 90 mg/dL, the investigators state.

Elevated glucose levels were most strongly linked to pancreatic cancer, doubling the risk of death from that malignancy in both genders. Other cancers significantly linked to high glucose levels included esophagus, liver, and colon/rectum in men and liver and cervix in women.

For many cancers, particularly esophageal and pancreatic, the risk of death rose as glucose levels climbed, the authors point out. The associations with cancer mortality were generally reflective of the patterns observed for cancer incidence.

"While the generalizability of the findings is uncertain, we have shown that fasting serum glucose level and diabetes are associated with cancer risk in a population far leaner than the Western populations in other studies," the investigators note. "These associations do not reflect confounding by obesity, suggesting that the mechanism of increased cancer risk reflects the consequences of hyperinsulinemia."

In a related editorial, Dr. Kathleen A. Cooney and Dr. Stephen B. Gruber, from the University of Michigan Medical School in Ann Arbor, comment that "as diabetes becomes an increasing public health concern in modern societies, the cancer risks looming on the horizon are now being recognized. Strategies to address the emerging epidemics of diabetes and obesity are likely to have a broad impact on public health."

Source: Diabetes In Control.com: JAMA 2005;194-202,235-236.