Researchers at the Albert Einstein College of Medicine (New York, NY, USA) conducted a prospective study involving a subsample of 4,902 nondiabetic women in the US Women's Health Initiative study to determine colorectal cancer risk. The researchers analyzed fasting blood samples, collected at baseline and during follow-up, for insulin and glucose. Cox proportional hazards models were used to assess associations with colorectal cancer risk in both baseline and time-dependent covariates analyses. Covariates in the analysis included age, body mass index (BMI), alcohol consumption, physical activity, ethnicity, and family history of colorectal cancer.

The results showed that compared with postmenopausal women whose baseline glucose levels were in the lowest tertile, those in the highest tertile had an adjusted hazard ratio for colorectal cancer of 1.74. The risk was even higher when the analysis was specifically for colon cancer. Of the 81 incident cases of colorectal cancer identified over 12 years of follow-up, 65 were colon cancer, 6 were malignancy in the rectosigmoid junction, and in the remaining 10 the cancer was rectal. The women who developed colorectal cancer were about two years older, were more often white, and were less likely to be physically active. Serum insulin and homeostasis model assessment were not associated with risk. The study was published in the November 29, 2011, issue of the British Journal of Cancer.

“In this cohort study of postmenopausal women, elevated fasting serum glucose, but not insulin or [the homeostasis model assessment of insulin resistance] was associated with roughly a twofold increased risk of colorectal cancer,” concluded lead author Geoffrey Kabat, MD. “These data suggest that elevated serum glucose levels may be a risk factor for colorectal cancer in postmenopausal women.”

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