In their quest to determine whether immune system surveillance guards against brain tumor development, researchers at The University of Texas M. D. Anderson Cancer Center have found that allergies and asthma that stimulate inflammation may be protective, but use of antihistamines to control the inflammation could eliminate that protection.
In this study, reported at the annual meeting of the American Association for Cancer Research (AACR), the researchers also associated chicken pox infection with a significantly reduced risk of developing brain tumors.
The researchers say the findings suggest that a small amount of inflammation in the brain may rev up the immune system enough to protect against brain tumor development. But they stress that no one should give up antihistamines or shun use of a chicken pox vaccine because of this study.
"Brain tumors are exceedingly rare, and many, many people use antihistamines, so we certainly are not suggesting a direct connection between the two, or between chicken pox and tumors," says the study's lead author, Melissa Bondy, Ph.D., a professor in the Department of Epidemiology. "What this study may do is help us begin to understand if the immune system plays a role in development of different kinds of brain tumors."
"Our long-term goal is to look at genes that may be increasing or reducing risk of developing these tumors, and then to assess whether some individuals might be genetically susceptible," says Michael E. Scheurer, Ph.D., a postdoctoral fellow in the Department of Epidemiology. As the study's first author, Scheurer will present the findings at the conference and also in a media briefing Tuesday, April 4 at 1 p.m.
In this study, Scheurer and Bondy combined data from their large Harris County, Texas, epidemiological study of brain tumor patients with information collected on patients in the San Francisco area by researchers at the University of California, San Francisco. Together, they compared medical histories of 830 brain tumor patients matched to a control group of 831 individuals. Within the patient group were 339 cases of glioblastoma (GBM), the most aggressive and lethal type of brain tumor, as well as 117 cases of midgrade anaplastic astrocytoma (AA) and 154 cases of low-grade gliomas (LGG).
The research team considered recent studies that suggest immune system activity in the brain may protect against brain tumor development and that people who have allergies or asthma have a reduced risk of developing a glioma.
"It could be that allergies and asthma produce enough inflammation in the brain to keep immune system cells active, and that this surveillance works to eliminate cancer beginning to develop in the brain," Scheurer says. "So we wondered whether use of antihistamines that counter that inflammation eliminates the protective effect."
They found that, indeed, a history of allergies and asthma was significantly protective for the three different kinds of brain tumors examined in the study. Individuals with the disorders had a 35 percent reduced risk of developing GBM, a 51 percent reduced risk of AA, and a 36 percent reduced risk of LGG.