People with both hay fever and asthma -- but not people with only one of these two conditions -- experienced an approximately 17 percent lower risk for dying from colorectal cancer, according to data presented at the 11th Annual AACR International Conference on Frontiers in Cancer Prevention Research, held in Anaheim, Calif., Oct. 16-19, 2012.
"Having both of these conditions could indicate that you are more likely to develop allergy-related immune responses that lower your risk for developing fatal colorectal cancer," said Eric Jacobs, Ph.D., strategic director of pharmacoepidemiology at the American Cancer Society.
In an earlier study published in 2005, researchers examined data from the Cancer Prevention Study II (CPS-II), a large prospective study of more than 1 million U.S. men and women who had been followed from 1982 to 2000. Results from this initial study showed that participants with both hay fever and asthma were at lower risk for developing fatal colorectal cancer.
In the current study, researchers looked again at data 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.
Jacobs and colleagues believe that the lower risk for fatal colorectal cancer among people with both hay fever and asthma may be a result of atopy, which is the general predisposition to develop allergic responses, including those that cause allergies and asthma. According to Jacobs, it is possible that individuals with atopy may sometimes mount an allergic-like response against colon cancer cells as well.
Future research could evaluate whether an association exists between other measures of atopy, such as blood levels of the immunoglobulin E antibody, and risk for developing or dying from colorectal cancer. If such an association is found, there could be implications for development of vaccines to stimulate anticancer immune responses in patients with colorectal cancer.
"If allergy-related immune responses are lowering colorectal cancer mortality in some individuals, that would imply that a similar kind of response might be inducible by a vaccine," Jacobs said.
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