Study Hints at Possible Allergy-Cancer Link

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Study Hints at Possible Allergy-Cancer Link

Some Types of Allergies May Increase the Risk of Blood Cancers

By  Warner

WebMD Medical News Reviewed By Brunilda Nazario, MD

on Wednesday, November 03, 2004

Nov. 3, 2004 -- People who suffer from some allergies, such as hives and

eczema, may have a higher risk of developing cancers of the blood later in life,

a

new study suggests.

Although previous studies have suggested that allergies may have the opposite

effect and help protect against cancer, Swedish researchers say their

findings indicate that certain types of allergies may increase the risk of some

blood

cancers, such as leukemia and non-Hodgkin's lymphoma.

" In our study, people with hives showed an increased risk of leukemia, " says

researcher Karin Söderberg, of the Karolinska Institutet in Sweden, in a news

release. " We also found an increased risk of non-Hodgkin's lymphoma among

individuals who had eczema during childhood. "

Further studies are needed to confirm these results. But experts say the

study raises interesting questions about the relationship between diseases that

affect the immune system, such as allergies, and the long-term risk of certain

blood cancers.

" It should not make people alarmed that just because they have allergies that

they could go on to develop malignancies, but it does add thought for future

studies, " says nne Frieri, MD, PhD, director of allergy immunology at

Nassau University Medical Center in East Meadow, N.Y.

Allergies Linked to Cancer?

In the study, which appears in the Nov. 4 issue of the journal BMC Public

Health, researchers followed a group of more than 16,000 twins for 31 years. The

twins filled out a questionnaire with information on allergies in 1967, and

researchers recorded whether they were diagnosed with a blood cancer during the

following years.

The study showed that people who reported hives and asthma were about twice

as likely to develop leukemia.

Researchers also found an increased risk of non-Hodgkin's lymphoma among

those who had eczema, an allergic disease that affects the skin. Childhood

eczema

appeared to double the risk of this type of cancer, but researchers say it's

important to point out that the likelihood of developing this rare condition is

still very small. The disease affects only about 0.03% of people in the U.S.

Other allergic conditions, such as hay fever, were not associated with any

increased risk of blood cancer.

Next: Competing Theories, More Study Needed

Competing Theories, More Study Needed

Researchers say that a link between allergic diseases and cancer risk has

been the subject of several studies, and two possible relationships have been

proposed.

The first, known as the immune surveillance hypothesis, holds that allergic

conditions may reduce cancer risk by enhancing the ability of the immune system

to detect and remove malignant cells.

The second theory argues that conditions that stimulate the immune system,

such as allergies, increase the risk of cancer. According to this theory,

constant stimulation of the immune system increases the number of

disease-fighting

white blood cells, which raises the risk of cancer-causing mutations of these

cells.

" There is a lot of controversy whether it's one theory or another, " says

Frieri, who is also professor of medicine and pathology at State University of

New

York at Stony Brook and a fellow of the American College of Asthma, Allergy

and Immunology.

Although some studies, including the present Swedish one, have supported both

arguments, other studies have also shown no relationship between allergic

diseases and cancer risk, or the results were inconsistent.

Researchers say one strength of this study was that the information about

allergic diseases and other possible confounding factors was collected after the

individuals were diagnosed with cancer, therefore eliminating any potential

recall bias. The study also involved a large number of participants who were

followed for more than 30 years.

But Frieri points out that there was only a small number of blood cancers

reported, which means that random variation in cancer rates cannot be excluded

as

a possible explanation of the findings. In addition, environmental factors

such as exposure to infections may have also played a role.

Frieri says cancer risk is dependent upon many factors and cannot be

explained by just allergies. Genes and other environmental, lifestyle, and

nutritional

factors all contribute to a person's overall risk of developing cancer.

Söderberg agrees and acknowledges that more research is needed before any

conclusive links are drawn between blood cancers and allergies.

" It is plausible that the association between allergic conditions and cancer

risk is complex and that the risk of developing cancer could depend on the

specific malignancy and could also be influenced by the type of allergic

condition, " write Söderberg and colleagues. " Clearly, these conflicting results

indicate that this area needs to be investigated further. "

SOURCES: Söderberg, K. BMC Public Health, Nov. 4, 2004; vol 4. News release,

BioMed Central. nne Frieri, MD, PhD, director of the Allergy and

Immunology, Nassau University Medical Center in East Meadow, N.Y.; professor of

Medicine and Pathology at State University of New York at Stony Brook. American

College of Asthma, Allergy and Immunology. American Academy of Allergy, Asthma

and

Immunology.

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