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Elevated glucose levels, diabetes may reduce risk for glioma
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Researchers observed an inverse relationship between blood glucose levels and risk for glioma, according to an analysis of two study cohorts published in Scientific Reports.
Blood glucose levels the year before cancer diagnosis had the greatest impact, suggesting excess glucose consumption by the preclinical tumor could account for the inverse relationship, researchers wrote.
“Diabetes and elevated blood sugar increase the risk for cancer at several sites including the colon, breast and bladder,” Judith Schwartzbaum, PhD, associate professor of epidemiology and a researcher at The Ohio State University Comprehensive Cancer Center, said in a press release. “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.”
No treatment option ensures long-term survival for patients with glioma. Further, symptoms typically only occur an average of 3 months prior to diagnosis, and thus it is important to identify indicators of the preclinical tumor before the onset of symptoms, the researchers wrote.
“Our research raises questions that, when answered, will lead to a better understanding of the mechanisms involved in glioma development,” Schwartzbaum said.
Researchers analyzed data from two large, long-term studies —AMORIS (n = 528,580) and Me-Can (n = 269,365) — to determine associations between prediagnostic blood glucose levels and risk for glioma.
The study cohort included patients with follow-up for a maximum of 15 years after their first blood glucose test until glioma diagnosis, death, emigration or the end of follow-up.
Glioma occurred at a rate of 7.6 per 100,000 person years in the AMORIS trial and 6.4 per 100,000 person years in the Me-Can trial.
In AMORIS, prediagnostic diabetes appeared inversely related with glioma risk (HR = 0.3; 95% CI, 0.17-0.63).
“This 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,” Schwartzbaum said. “For example, insulin-like growth factor is associated with glioma recurrence and is found in lower levels in people with diabetes than those who don’t have the disease.”
Among men in AMORIS with blood collected within 1 year before the conclusion of follow-up, glioma rates decreased 22% per unit increase of the standardized natural log of blood glucose (HR = 0.78; 95% CI, 0.65-0.94).
However, this association did not persist in the Me-Can cohort (HR = 0.99; 95% CI, 0.63-1.56).
Trend tests for both men and women indicated the presence of an inverse linear trend (Ptrend = 0.04) over the levels of time before diagnosis.
“Thus, the time of blood draw modifies the effect of glucose on the glioma rate; that is, there is a statistically significant interaction between time and glucose,” the researchers wrote.
Age at glioma diagnosis appeared to modify the association between glucose and glioma risk among men aged older than 70 years in Me-Can (HR = 0.5; 95% CI, 0.29-0.85); however, this association did not appear in the AMORIS trial (HR = 0.84; 95% CI, 0.64-1.11).
Additional investigation of a prediagnostic Warburg effect and associations between blood glucose level and glioma by genetic subtypes of type 2 diabetes and glioma may be warranted, according to the researchers.
“The brain accounts for only about 2% of body weight, but consumes about 20% of the body’s available glucose,” Schwartzbaum said. “The body of research on restrictive diets and their effect on brain cancer development has shown mixed results, and more work is needed to determine if there’s something about the sugar–tumor relationship that can be modified in a way that’s beneficial to brain cancer patients.” – by Kristie L. Kahl
Disclosure: The researchers report no relevant financial disclosures.
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