Diabetes Raises Risk for Many Cancers, but Not Glioma

Diabetes Raises Risk for Many Cancers, but Not Glioma

Many cancers, such as colon, breast and bladder, are more common among patients who have elevated blood sugar and diabetes. However, recent research finds the opposite relationship when it comes to brain tumors. Gliomas are less common among patients with elevated blood sugar and diabetes, according to research published in Scientific Reports.

Glioma is one of the most common types of cancerous brain tumors. It is typically diagnosed at middle age, and although there are treatments in development, no current therapy ensures long-term survival.

The study’s lead author Judith Schwartzbaum, PhD, associate professor of epidemiology and a researcher at The Ohio State Comprehensive Cancer Center, has led previous research studies which found that high blood sugar appears to reduce a person’s risk of meningioma, a noncancerous brain tumor.

Schwartzbaum noted that the inverse relationship she and her colleagues found, “may suggest that the tumor itself affects blood glucose levels or that elevated blood sugar or diabetes may paradoxically be associated with a protective factor that reduces brain tumor risk.”

This study combined data from 2 large, long-term studies. The AMORIS study included 528,580 Swedish patients, and the study known as Me-Can included 269,365 patients from Austria and Sweden. Overall from both groups, a total of 812 patients developed gliomas.

Researchers evaluated the data on blood sugar and diabetes, and the relationship to the subsequent development of brain cancer. Those with elevated blood sugar and diabetes were found to have a lower risk of developing glioma. This relationship was the strongest within 1 year of cancer diagnosis.

“Diabetes and elevated blood sugar increase the risk of cancer at several sites including the colon, breast and bladder,” Schwartzbaum said in a statement. “But in this case, these rare malignant brain tumors are more common among people who have normal levels of blood glucose than those with high blood sugar or diabetes.”

“Elevated consumption of blood glucose by the preclinical tumor may account for the apparent reduction of glioma risk among people with diabetes or elevated blood glucose level,” according to the study authors. They cited a phenomenon called the Warburg effect whereby cancer cells, in general, consume more glucose than nonproliferating cells. If this effect were present, the authors explained, the inverse association between the tumor and blood sugar levels would be the strongest near the time of the glioma diagnosis.

The authors stated that although their findings further support the inverse association between blood sugar and glioma, evidence for the presence of the Warburg effect as the cause of this relationship was mixed. Data from the AMORIS study supported this effect, but data from the Me-Can study did not.

Other studies evaluating restrictive diets and their effect on brain cancer development have yielded mixed results. More research is needed to determine whether there is some way to modify the sugar/tumor relationship that will benefit patients with brain cancer.

Schwartzbaum J, Edlinger M, Zigmont V, et al. Associations between prediagnostic blood glucose levels, diabetes, and glioma. Sci Rep. 2017;7(1):1436.