June 7, 2002
NEW YORK (Reuters Health) - Allergies and autoimmune conditions such as lupus and multiple sclerosis may reduce the risk of glioma, according to the results of a new study. The reasons for the association are unclear, but the findings suggest that immunologic factors may be involved.
In most cases, the cause of brain malignancies is unknown. A few hereditary syndromes increase the risk, but they only account for less than 5% of all cases. The only proven environmental risk factor is exposure to ionizing radiation.
Recently, several reports have raised the possibility that people with overstimulated immune systems may have a reduced risk of brain cancer.
To see whether autoimmune disease and allergies offer any protection against brain cancer, a team led by Dr. Alina V. Brenner, from the National Cancer Institute in Bethesda, Maryland, compared 782 people hospitalized with a brain tumor with 799 patients hospitalized for other causes.
Having allergies or an autoimmune disease reduced the risk of some, but not all, types of brain tumors, the researchers report in the May 10th issue of the International Journal of Cancer. The risk of a glioma was reduced 33% in people with a history of allergies and 51% in those with an autoimmune disease. The risk was lowest in people who had both allergies and an autoimmune disease.
The risk of meningioma was lower in people with an autoimmune disease, but not in those with allergies, the report indicates.
The finding of a reduced risk of glioma in people with a history of allergies or autoimmune diseases is consistent with previous reports, Dr. Brenner told Reuters Health. "Given that so little is known about factors that influence the risk of glioma, this finding is particularly exciting," she added.
She cautioned, however, that "at this point, it is premature to draw definite conclusions about the underlying basis of the association."
There are several possible explanations for the apparent reduction in risk, according to Dr. Brenner. Immune factors that are involved in or predispose people to autoimmunity or allergies might play a role. It is also possible that medications used to treat these conditions may offer some protection. Other non-immunologic factors may also be involved.
"Clearly, this is a promising area of research that warrants further investigation," Dr. Brenner noted.
Int J Cancer 2002;99:252-259.
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