A new study from the American Cancer Society concludes people with both hay fever and asthma — but not people with only one of the conditions — have an approximately 17 percent lower risk of death from colorectal cancer. The study, led by Eric J. Jacobs, Ph.D., strategic director of pharmacoepidemiology, is being presented at the 11th Annual AACR International Conference on Frontiers in Cancer Prevention Research.
The study revisits findings from a 2005 American Cancer Society that linked a history of both hay fever and asthma to a lower risk of fatal colorectal cancer. For the new study, Dr. Jacobs and colleagues re-analyzed from the more than 1 million participants in CPS-II who did not have cancer at the start of the study and were followed through 2008. They also examined data from the Cancer Prevention Study I, a similarly sized study, in which participants were followed from 1959 to 1972.
The combined results from the CPS-I and CPS-II studies, including more than 19,000 deaths from colorectal cancer, confirmed the findings from the earlier study: People with hay fever and asthma had an approximately 17 percent lower risk for dying from colorectal cancer. People with only hay fever or only asthma had little reduction in risk for fatal colorectal cancer.
We asked Dr. Jacobs about the study.
How did this work come to be? Why study the connection between these two seemingly unrelated chronic diseases?
“The immune system in general is thought to play a role in preventing cancer through a process called ‘immune surveillance’ and allergic responses are one type of immune system response. Hay fever and asthma are both related to allergy; most, though not all, asthma involves allergy related immune responses in the lungs.
“The current study was inspired by an earlier study published in 2005, which looked at the relationship between hay fever and asthma and risk of dying from any of 12 different cancers in the Cancer Prevention Study II cohort. A notable finding from that study was that among people without cancer at the start of the study, those who had both hay fever and asthma had about a 24% lower risk of developing a fatal colorectal cancer.
“One possible explanation for this finding is that many people with both hay fever and asthma may have a general tendency to develop allergic responses, and these individuals may sometimes mount an allergy-related immune response against colorectal cancer which inhibits the development or progression of the cancer. However, almost no other studies have examined whether people with multiple allergy related conditions are at lower risk of developing or dying from colorectal cancer, so we felt it was important to confirm the earlier results from Cancer Prevention Study II.”
Was the strength of the association about what you expected?
“We had little expectation about how strong this association might be because almost no other studies have examined colorectal cancer risk in people with more than one allergy-related condition. Although having both hay fever and asthma was linked with lower risk of fatal colorectal cancer in the earlier CPS-II analysis, the nature of research is that initially intriguing findings are often not confirmed in later studies. The approximately 17% lower risk of fatal colorectal cancer in the new combined analysis is not large, but nonetheless provides a clue that allergy-related immune responses might inhibit the development or progression of colorectal cancer.”
What are the implications of this work? What does it mean for individuals and for us as a society?
“This work does not have immediate implications. People who have both asthma and allergies may be cheered by the idea that their allergic tendencies might have some type of health benefit. The findings do, however, provide a clue that allergy-related immune responses might inhibit colorectal carcinogenesis. Future research needs to be conducted to determine if naturally occurring allergy-related immune responses sometimes help fight colorectal cancer. If they do, it would raise the possibility that therapeutic vaccines could be developed that could stimulate similar anti-cancer immune responses in people with colorectal cancer.”