People suffering from prediabetes, a term referring to the intermediate stage between normoglycemia and overt diabetes mellitus, stand a 15 to 30 percent higher risk of developing type 2 diabetes. A recent study conducted at the First People's Hospital of Shunde in China has revealed that people who develop prediabetes also increase their risk of also being diagnosed with certain types of cancer by 15 percent.

"These findings have important clinical and public health implications,” the authors of the study said in a statement. “For example, in the U.S. population aged ≥18 years, the age-adjusted prevalence of prediabetes increased from 29 percent in 1999–2002 to 36 percent in 2007–2010. Many other countries, both developed and developing, are also seeing steep rises in the number of people with both full-blown type 2 diabetes and prediabetes. Considering the high prevalence of prediabetes, as well as the robust and significant association between prediabetes and cancer demonstrated in our study, successful intervention in this large population could have a major public health impact."

Lead researcher Professor Yuli Huang and his colleagues gathered data using 16 studies, including one from Africa, four from Asia, and 11 from the United States and Europe, to evaluate the cancer risk associated with impaired fasting glucose (IFG) and impaired glucose tolerance (IGT) populations. After controling for cancer endpoints, including age, ethnicity, and duration of follow-up, the research team found a 15 percent increase in overall cancer risk associated with prediabetes. Results were the same for prediabetes patients affected by both IFG and IGT.

Prediabetes significantly increased a person’s risk of developing stomach, colon, liver, pancreas, breast, and endometrium cancer, but not lung, prostate, ovary, kidney, or bladder cancer. While obesity tends to be included as a risk factor for diabetes, it is also associated with cancer development. In a separate analysis that controled for obesity, researchers still found that prediabetes on its own increased cancer risk by 22 percent.

"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,” the authors added. “Notably, metformin mediates an approximately 30 percent reduction in the lifetime risk of cancer in diabetic patients. However, whether this is true in prediabetic individuals is not yet known. Long-term, large-scale studies of high-risk individuals, especially those with IGT or a combination of IGT and IFG, are urgently needed to explore the effects of metformin interventions on the risk of cancer in people with prediabetes."

Researchers gave three explanations as to why prediabetes increases cancer risk. Conditions related to chronic hyperglycemia, such as oxidative stress and the accumulation of glycated endproducts, could be carcinogenic. Increased insulin resistance may also lead to increased insulin secretion, giving cancers cells the ability to grow and divide. Lastly, genetic mutations, most notably the malfunction of a tumor suppressor gene, could predispose patients to a higher risk of cancer development.

Source: Huang Y, et al. Study of almost 900,000 people shows prediabetes increases the risk of cancer by 15%. Diabetologia. 2014.