New research indicates that older women with diabetes face a more than doubled risk for some types of colorectal cancer.
Diabetes has been identified as a colon cancer risk factor, but the mechanisms aren't completely understood.
For this population-based cohort study, a research team, led by Mayo Clinic physicians, examined data from 37,695 participants of the Iowa Women's Health Study (IWHS), which enrolled women aged 55 in 1986 and remains ongoing.
Of these women, 2,361 reported a diagnosis of Type 2 diabetes and 1,200 developed colorectal cancer.
To find the links between colorectal cancer and diabetes, the researchers worked with regional pathology laboratories to obtain tumor tissue samples from IWHS participants who were diagnosed with colorectal cancer.
They linked the tissue samples with other IWHS data, looking for cancer pathways and risk factors, and whether those risk factors were associated with three different molecular markers: microsatellite instability (MSI), CpG island methylation (CIMP), and BRAF gene mutations.
"Diabetes was more strongly associated with the MSI-high, CIMP-positive and BRAF-mutation cancer subtypes in this group of older women," said Mayo Clinic gastroenterologist Paul Limburg.
Limburg explained that diabetes appeared to confer a greater than twofold increase in risk for these molecularly-defined tumors, compared to women without diabetes.
The findings are being presented at Digestive Disease Week 2010, the annual meeting of the American Gastroenterological Association.