COLUMBUS, Ohio - New research adds to the growing body of evidence
suggesting that there’s a link between allergies and reduced risk of a
serious type of cancer that starts in the brain. This study suggests the
reduced risk is stronger among women than men, although men with
certain allergy profiles also have a lower tumor risk.
also strengthens scientists’ belief that something about having
allergies or a related factor lowers the risk for this cancer. Because
these tumors, called glioma, have the potential to suppress the immune
system to allow them to grow, researchers have never been sure whether
allergies reduce cancer risk or if, before diagnosis, these tumors
interfere with the hypersensitive immune response to allergens.
conducting this study were able to analyze stored blood samples that
were taken from patients decades before they were diagnosed with glioma.
Men and women whose blood samples contained allergy-related antibodies
had an almost 50 percent lower risk of developing glioma 20 years later
compared to people without signs of allergies.
“This is our most
important finding,” said Judith Schwartzbaum, associate professor of
epidemiology at Ohio State University and lead author of the study. “The
longer before glioma diagnosis that the effect of allergies is present,
the less likely it is that the tumor is suppressing allergies. Seeing
this association so long before tumor diagnosis suggests that antibodies
or some aspect of allergy is reducing tumor risk.
“It could be
that in allergic people, higher levels of circulating antibodies may
stimulate the immune system, and that could lower the risk of glioma,”
said Schwartzbaum, also an investigator in Ohio State’s Comprehensive
Cancer Center. “Absence of allergy is the strongest risk factor
identified so far for this brain tumor, and there is still more to
understand about how this association works.”
studies of the link between allergies and brain tumor risk have been
based on self-reports of allergy history from patients diagnosed with
glioma. No previous studies have had access to blood samples collected
longer than 20 years before tumor diagnosis.
The current study
also suggested that women whose blood samples tested positive for
specific allergy antibodies had at least a 50 percent lower risk for the
most serious and common type of these tumors, called glioblastoma. This
effect for specific antibodies was not seen in men. However, men who
tested positive for both specific antibodies and antibodies of unknown
function had a 20 percent lower risk of this tumor than did men who
Glioblastomas constitute up to 60 percent of
adult tumors starting in the brain in the United States, affecting an
estimated 3 in 100,000 people. Patients who undergo surgery, radiation
and chemotherapy survive, on average, for about one year, with fewer
than a quarter of patients surviving up to two years and fewer than 10
percent surviving up to five years.
The study is published online in the Journal of the National Cancer Institute.
and colleagues were granted access to specimens from the Janus Serum
Bank in Norway. The bank contains samples collected from citizens during
their annual medical evaluations or from volunteer blood donors for the
last 40 years. Norway also has registered all new cases of cancer in
the country since 1953, and personal identification numbers enable
cross-referencing those cases with previously collected blood samples.
researchers analyzed stored samples from 594 people who were diagnosed
with glioma (including 374 diagnosed with glioblastoma) between 1974 and
2007. They matched these samples for date of blood collection, age and
sex with 1,177 samples from people who were not diagnosed with glioma
The researchers measured the blood samples for
levels of two types of proteins called IgE, or immunoglobulin E. This is
a class of antibodies produced by white blood cells that mediate immune
responses to allergens. Two classes of IgE participate in the allergic
response: allergen-specific IgE, which recognizes specific components of
an allergen, and total IgE, which recognizes these components but also
includes antibodies with unknown functions.
In each sample, the
scientists determined whether the serum contained elevated levels of IgE
specific to the most common allergens in Norway as well as total IgE.
The specific respiratory allergens included dust mites; tree pollen and
plants; cat, dog and horse dander; and mold.
The researchers then
conducted a statistical analysis to estimate the association between
elevated concentrations of allergen-specific IgE and total IgE and the
risk of developing glioma.
Among women, testing positive for
elevated levels of allergen-specific IgE was associated with a 54
percent decreased risk of glioblastoma compared to women who tested
negative for allergen-specific IgE. The researchers did not see this
association in men.
However, the relation between total IgE
levels and glioma risk was not different for men and women,
statistically speaking. For men and women combined, testing positive for
elevated total IgE was linked to a 25 percent decreased risk of glioma
compared with testing negative for total IgE.
The analysis for
effects on glioblastoma risk alone suggested a similar decreased risk
for both men and women combined whose samples tested positive for high
levels of IgE, but the findings were considered borderline in terms of
statistical significance, meaning the association could also be
attributed to chance.
“There is definitely a difference in the
effect of allergen-specific IgE between men and women. And even results
for total IgE suggest there still may be a difference between the sexes.
The reason for this difference is unknown,” Schwartzbaum said.
the study does provide evidence for, however, is the likelihood that
the immune systems of people with respiratory allergies could have a
protective effect against this type of brain cancer. The ability to
investigate this association over four decades between blood sampling
and tumor diagnosis gave the researchers better insight into the
relationship between allergies and tumor risk, Schwartzbaum said.
example, a positive test for elevated concentrations of total IgE was
associated with a 46 percent decreased risk for developing a glioma 20
years later compared to samples testing negative for elevated IgE,
according to the analysis. That decreased risk was only about 25 percent
in samples that tested positive for high levels of total IgE taken two
to 15 years prior to diagnosis.
“There may be a trend - the
closer the samples get to the time of diagnosis, the less help the IgE
is in decreasing the risk for glioma. However, if the tumor were
suppressing allergy, we would expect to see a bigger difference in risk
near the time of diagnosis,” Schwartzbaum said.
plans to further analyze the serum samples for concentration of
cytokines, which are chemical messengers that promote or suppress
inflammation as part of the immune response, to see if these proteins
have a role in the relationship between elevated IgE levels and lowered
This work was funded by the National Cancer
Institute, the National Institutes of Health and a Research Enhancement
and Assistance Program grant from Ohio State’s Comprehensive Cancer
Co-authors include Bo Ding, Anders Ahlbom and Maria
Feychting of the Karolinska Institutet in Stockholm, Sweden; Tom Borge
Johannesen and Tom Grimsrud of the Cancer Registry of Norway; Liv Osnes
of Ulleval University Hospital in Oslo, Norway; and Linda Karavodin of
Karavodin Preclinical Consulting in Encinitas, Calif.This article was first published at www.newswise.com