A team of scientists looking into the interplay of the immune system and cancer have found a link between a having a history of airborne allergies—in particular to plants, grass, and trees—with risk of blood cancers in women.

Notably, the study did not find the same association in men, which suggests a possible gender-specific role in chronic stimulation of the immune system that may lead to the development of hematologic cancers. The findings were published in the American Journal of Hematology (2013; doi:10.1002/ajh.23564).

“To the best of our knowledge, ours is the first study to suggest important gender differences in the association between allergies and hematologic malignancies,” wrote lead author Mazyar Shadman, MD, MPH, a senior fellow in the Clinical Research Division at Fred Hutchinson Cancer Research Center in Seattle, Washington.

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Shadman said that the immune system’s potential role in cancer causation is a focus of intense scientific interest. “If your immune system is over-reactive, then you have problems; if it’s under-reactive, you’re going to have problems. Increasing evidence indicates that dysregulation of the immune system, such as you find in allergic and autoimmune disorders, can affect survival of cells in developing tumors.”

For the study, the researchers drew on a large, population-based sample of men and women from the vitamins and lifestyle (VITAL) cohort, which included people age 50 to 76 years from western Washington. The study participants answered a 24-page questionnaire that focused on three major areas: health history and cancer risk factors, medication and supplement use, and diet. History of asthma and allergies was also taken, including allergies to plants, grasses, or trees; mold or dust; cats, dogs, or other animals; insect bites or stings; foods; and medications.

Of the participants, 681 developed a hematologic malignancy during the follow-up period. These participants were more likely to be male, to have two or more first-degree relatives with a family history of leukemia or lymphoma, to be less active, and to rank their health status as low. A history of allergies to airborne antigens was associated with a higher risk of hematologic malignancies. The most statistically significant association was seen with allergies to plants, grass, and trees.

Furthermore, the study looked at associations between the different subtypes of allergies and hematologic malignancies and found that a history of allergies to plants, grass, and trees was significantly associated with mature B-cell neoplasms, one of four major categories of lymphoma. There was also an increased risk of plasma-cell neoplasms for participants who reported a history of allergies to cats, dogs, or other animals. Plasma-cell neoplasms are both cancerous and noncancerous conditions, in which the body makes too many plasma cells.

When stratified by gender, the incidence of blood cancers in response to these allergens was increased in women but not in men. The reason for this is as yet unknown.