Prediabetes and Cancer: Is There a Link?

By Athena Philis-Tsimikas, M.D.

Published Sep 17, 2014

By Athena Philis-Tsimikas, MD, Special to Everyday Health
A new research study has troublesome news for the 86 million Americans who have a condition known as prediabetes: Not only are you at high risk for developing type 2 diabetes, you also may have an increased risk of cancer.
People with prediabetes have blood glucose levels that are higher than normal, but not yet high enough to qualify as diabetes. A diagnosis of prediabetes includes individuals with impaired glucose tolerance (IGT), impaired fasting glucose (IFG), or a combination of both.
Despite the fact that the number of Americans diagnosed with type 2 diabetes is skyrocketing, the disease does not develop overnight. Instead, blood glucose levels generally increase over time as a result of lifestyle factors, such as poor diet, lack of exercise, and obesity. Aging alone also contributes to decline in beta cell function of the pancreas and onset of diabetes. If this increase in blood sugar isn’t controlled, prediabetes will likely result, followed by full-blown type 2 diabetes within 10 years.
Now, research shows that prediabetes can also raise your risk of developing cancer, according to a study just published in Diabetologia, the journal of the European Association for the Study of Diabetes. The article, a meta-analysis that included a total of 16 studies and 891,426 participants from the US, Europe, Asia, and Africa, shows that prediabetes raises overall cancer risk by 15 percent. Delving deeper into specific types of cancer risk, the analysis found that prediabetes was significantly associated with increased risks of cancer of the stomach and colorectum, liver, pancreas, breast, and endometrium. No significant association was found between prediabetes and cancer of the bronchus amd lung, prostate, ovary, kidney, or bladder.

Know Your Risk Factors

Why would prediabetes increase cancer risk? One factor that stands out is obesity. Being overweight or obese is a main risk factor for diabetes and has been associated with an increased risk of cancer as well. However, the authors of the study addressed this by including a sub-analysis of only studies that accounted for obesity by adjusting for body mass index (BMI). They found that, even after controlling for weight, prediabetes still increased the risk of cancer by 22 percent.
The authors do offer several other possible explanations for the increased risk. Chronic high blood sugar levels, or hyperglycemia, can produce chronic oxidative stress, which is basically a disparity between the body’s production of cancer-causing free radicals and its ability to fight off their harmful effects. Excessive hyperglycemia also can lead to the production of potentially harmful substances known as advanced glycated endproducts (AGEs) that may cause cancer and other diseases.
In addition, say the authors, increased insulin resistance can increase insulin secretion, which can, in turn, promote cancer cells to grow and divide. Third, there could be genetic mutations that predispose individuals to an increased risk of cancer, with one recent study showing that a malfunction in a tumor suppressor gene exposed individuals to increased risk of both cancer and prediabetes.
They add: “It should be noted that metformin — one of several first line therapies available to treat type 2 diabetes — is now considered as having some ‘protective’ anticancer properties. Notably, metformin mediates an approximately 30 percent reduction in the lifetime risk of cancer in diabetic patients.” However, whether this is true in individuals with prediabetes is not yet known; another retrospective cohort study just published this month concluded that use of metformin does not affect cancer risk. More research is needed on this issue.

Change Your Diabetes Destiny

With the number of Americans developing prediabetes (and type 2 diabetes) continuing to rise every year, taking steps to protect your health has never been more important. Having prediabetes does not mean you are destined to develop type 2. By making lifestyle changes to help lower your blood sugar levels, such as losing weight and increasing exercise, you can significantly reduce the risk.
Athena Philis-Tsimikas, M.D., is an endocrinologist and the corporate vice president for the Scripps Whittier Diabetes Institute at Scripps Health in San Diego.