ALLERGIES AND HEMATOLOGIC CANCER RISK

Women with airborne allergies could be at higher risk for hematologic malignancies than women without allergies, researchers contend.

Data from a prospective cohort study of more than 66,000 older adults in Washington state found that women with any airborne allergen had a 47% increase in risk for a hematologic cancer. In addition, women who hit the allergy trifecta of sensitivity to plants, grass, and trees had a 73% greater chance of developing a mature B-cell lymphoma or related disorder.

Overall, men were more likely than women to develop a hematologic malignancy, but the risk in men was not significantly associated with allergic status, write Mazyar Shadman, MD, MPH, and colleagues from the Fred Hutchinson Cancer Research Center in Seattle.

The study was published in the December issue of the American Journal of Hematology.

The overall incidence of hematologic malignancies in the cohort was 1.03%, and was significantly higher in men than in women (P < .001).

"It is tempting to speculate that the additional effect of allergy may reach statistical significance in women because of their lower baseline risk for the development of hematologic malignancies compared to men," the researchers write.

"However, hormonal effects on the immune system and interactions with carcinogenesis may offer an alternative biological explanation that will require further mechanical studies, in particular if our findings are replicated in an independent study cohort," they explain.

The researchers are careful to point out that "given the limited number of cases within each subtype of hematologic cancer, the risk estimates need to be interpreted with caution in our subtype analyses, and the possibility of chance finding due to multiple testing should be recognized."

"All Over the Map"

A cancer epidemiologist who has studied possible associations between allergies and leukemia in adults told Medscape Medical News that the study is very strong but, through no fault of the researchers, the subject at hand is distinctly fuzzy.

"The problem — and they sort of point it out in their discussion — is that the results for allergies and cancer are all over the map. Some studies show inverse relationships and some studies show direct relationships," said Richard G. Stevens, PhD, professor of cancer epidemiology at the University of Connecticut Health Center in Farmington.

The researchers note that previous studies have found sex differences in the association of allergies with head and neck cancers (PloS One. 2013;8:e55138) and in allergen-specific immunoglobulin E levels and glioblastoma (J Natl Cancer Inst. 2012;104:1251-1259).

However, Dr. Stevens pointed out that in each of the above studies, allergies are associated with a decreased risk for cancer. He was involved in a study that found that the risk for acute myeloid leukemia was lower in people with allergies, and that the risk declined as the number of specific allergies reported by study subjects increased (J Clin Epidemiol. 1989;42:995-1001). The study also found that the risk was lower in people who reported a history of asthma, eczema, and hives, suggesting an atopic/allergic phenotype.

Dr. Stevens told Medscape Medical News that the issue of a possible relation between allergies and hematologic cancers is intriguing but difficult to tease out.

"For other cancers, the idea long ago was that if you have allergies, your immune system is kind of hyperactive, and that should lower your risk for other cancers," he explained. However, he added, "for hematologic cancers, you could go either way, because immune surveillance would be good but, if you have allergies, that means that cells are dividing more to mount the immune response, increasing the chance of mutations."

VITAL Cohort

Dr. Shadman and colleagues acknowledge that there have been discordant results in studies looking for links between allergies and hematologic malignances. To try to clear up the confusion, they looked at data from the large prospective Vitamins and Lifestyle (VITAL) cohort study.

The researchers collected data on 66,212 men and women 50 to 76 years of age who lived in western Washington and had participated in the VITAL study. The subjects had all filled out a 24-page, sex-specific, self-administered questionnaire that asked questions about allergies, personal medical history, and family history of leukemia and lymphoma.

The incidence of hematologic malignancies was determined from the Surveillance, Epidemiology, and End Results cancer registry for the region.

There were 681 incident cases of hematologic cancers from 2000 to 2009. In addition to the higher incidence in women, those who developed hematologic cancers were more likely to be older than those who did not (mean age, 65.2 vs 61.4 years; P < .001), more likely to have 2 or more first-degree relatives with a family history of leukemia or lymphoma (P = .002), more likely to have poorer health (P < .03), and less likely to be physically active.