Colorectal cancer and diabetes; an increased risk of mortality?

The authors aimed to evaluate the association between diabetes and risk of death in colorectal cancer patients.

Previous studies have reported that diabetes (a group of metabolic diseases in which a person has a high blood sugar) significantly increases overall mortality (death) in patients with colorectal cancer. However, it is unclear whether the higher rate of mortality is driven by a worse colorectal cancer outlook or by competing diabetes-associated risks such as increased risk of cardiovascular disease (related to the heart, arteries and veins).

The authors aimed to evaluate if diabetes influenced colorectal cancer-specific mortality. Of a total of 61,213 colorectal cancer patients in a US database, 14,813 (24.2%) had diabetes. Of these, 83% had diabetes-related complications while 17% did not. Over an average follow-up of 38 months, 46.9% of patients died from all causes and 25.9% of patients died from colorectal cancer.

Compared to patients without diabetes, colorectal cancer patients with pre-existing diabetes had a 20% increased risk of mortality. The risks of mortality were more pronounced for patients who had diabetes with complications with a 63% increased risk compared to those with no diabetes.

Diabetes was significantly associated with mortality related to cardiovascular disease regardless of the site of the cancer, particularly for diabetes with complications. In contrast, there was no significantly increased risk for mortality directly related to colorectal cancer in diabetes patients.

The authors concluded that although pre-existing diabetes increases the risk of mortality in colorectal cancer patients, this is attributable to cardiovascular factors rather than colorectal cancer factors.

This study relied on existing public health surveillance and administrative information that were not designed for this particular research purpose.