Study Links Diabetes, Colorectal Cancer

New research has found evidence confirming that patients with diabetes mellitus (DM) have a higher risk of developing colon cancer (CC).

Researchers from the University of California, Berkeley, analyzed 14 international studies. They found that people with DM had a 38% higher risk of being diagnosed with colon cancer than those without the disease. Men with DM also had a 20% higher risk of rectal cancer (RC) than their non-diabetic peers, the researchers found.

“These data suggest that diabetes mellitus is an independent risk factor for colon and rectal cancer,” the authors wrote in the abstract for the study, which was published recently in the American Journal of Gastroenterology. “This information can inform risk models and specialty society CRC [colorectal cancer] screening guidelines.”

Although DM has been associated with an increased risk of CRC, when the American College of Gastroenterology Guidelines for Colorectal Cancer Screening 2008 recommend that clinicians be aware of an increased CRC risk in patients with smoking and obesity, they did not highlight the increase in CRC risk in patients with DM.

Berkeley researcher Hiroki Yuhara, MD, and is colleagues conducted a meta-analysis of case—control and cohort studies. They identified and evaluated 14 studies to see whether the association between DM and CRC varied by sex; they also assessed potential confounders including obesity, smoking, and exercise.

“DM was associated with an increased risk of CC (summary RR 1.38, 95% CI 1.26—1.51; n=14 studies) and RC (summary RR 1.20, 95% CI 1.09–1.31; n=12 studies),” the researchers wrote in the study abstract. This association remained when the researchers limited the meta-analysis to studies that either controlled for smoking and obesity or for smoking, obesity, and physical exercise.

“DM was associated with an increased risk of CC for both men (summary RR 1.43, 95% CI 1.30—1.57; n=11 studies) and women (summary RR 1.35, 95% CI 1.14–1.53; n=10 studies). For RC, there was a significant association between DM and cancer risk for men (summary RR 1.22, 95% CI 1.07–1.40; n=8 studies), but not for women (summary RR 1.09, 95% CI=0.99–1.19; n=8 studies).”

They added that they were comfortable with the study’s findings. “Although these findings are based on observational epidemiological studies that have inherent limitations due to diagnostic bias and confounding, subgroup analyses confirmed the consistency of our findings across study type and population.”

SourceIs Diabetes Mellitus an Independent Risk Factor for Colon Cancer and Rectal Cancer? [American Journal of Gastroenterology]