Cancer’s sweet tooth may play a role in increasing the risk of lethal prostate cancers, according to researchers at the Johns Hopkins Kimmel Cancer Center and the Johns Hopkins Bloomberg School of Public Health. The findings are preliminary results from a review of data collected among more than 5,000 men enrolled in the Atherosclerosis Risk in Communities Study, a prospective national study of heart disease that began in 1987. In addition to tracking heart disease risk factors, data were collected on three tests, or biomarkers, that measure glucose levels in the blood. The tests included glucose levels after fasting; the A1c test, a measure of how much hemoglobin in the blood has been tagged with glucose; and the glycated albumin test, a measure of albumin protein molecules that have bonded with glucose in the blood.
Previous studies have shown inconsistent results for the association between hyperglycemia, or high blood sugar levels, and prostate cancer death depending whether fasting glucose or the A1c test was used to measure glucose. The reasons why hyperglycemia may be linked with prostate cancer death are not well-understood, but the researchers say it may promote how cancer cells multiply and proliferate. “We wanted to understand why different biomarkers of glucose had different associations with prostate cancer death,” says Michael Marrone, pre-doctoral student at the Johns Hopkins Bloomberg School of Public Health.
To do that, the researchers used all three biomarkers to better classify normal blood sugar levels and hyperglycemia. The researchers analyzed survival time of 5,276 men between 1990 and 1992 through the end of 2012, totaling 96,617 “person-years,” a factor that reflects the accumulation of participants’ follow-up visits with study coordinators. Analyzing the data, the researchers found that 69 men had died of prostate cancer by 2012. Nine of them had low glycemia, five were in the normal range, 30 had high levels of one of the three glycemia tests, 16 registered high on two tests, and three were high on all three tests. Six men had previously diagnosed diabetes. Men who were classified as hyperglycemic on all three of the tests had nearly five times increased risk of prostate cancer death, compared with men who were classified as normal on all three glycemia tests. Men classified as hyperglycemic using one of the tests had twice the risk of dying of prostate cancer compared to men who were classified as normal on the three tests. The researchers also found a higher risk of prostate cancer death in men who registered hyperglycemic on two of the tests, although the result was not statistically significant.
Similar trends were found between African-American and Caucasian men. The results support findings of similar previous studies, but the investigators caution that the small size of the group limits their ability to draw definitive conclusions.
“We need to explore glycemia further in larger groups of men, so that we can tease out the molecular mechanisms of these potential links between glucose levels and prostate cancer,” says Corinne Joshu, Ph.D., assistant professor of epidemiology in the Johns Hopkins Bloomberg School of Public Health and member of the Johns Hopkins Kimmel Cancer Center. “Hyperglycemia is associated with risk factors in many adverse health outcomes, and people should be aware of this.”