Allergies and Asthma in Relation to Cancer Risk

Background: Allergies and asthma, conditions commonly characterized by immunoglobulin E-mediated atopic reactions, may decrease cancer risk via increases in immunosur-veillance, but may increase risk due to persistent immune stimulation. Associations between allergies and asthma and cancer risk remain unclear, and it is unknown whether associations vary by race/ethnicity. Methods: We evaluated these associations in the Southern Community Cohort Study. At baseline (2002-2009), 64,170 participants were queried on history of allergies and asthma; participants were followed through 2011, during which time 3,628 incident, invasive cancers were identified, including 667 lung cancers, 539 breast cancers, and 529 prostate cancers. Cox proportional hazards regression was used to estimate multivariable-adjusted HRs and 95% confidence intervals (CI). Results: Neither allergies nor asthma was associated with risk of developing invasive cancer overall. Asthma was associated with increased lung cancer risk (HR, 1.25; 95% CI, 1.00-1.57), with no variation by race/ethnicity (P-interaction = 0.84). Conversely, history of allergies was associated with decreased lung cancer risk (HR, 0.80; 95% CI, 0.65-1.00), with an inverse association observed among non-Hispanic whites (HR, 0.65; 95% CI, 0.45-0.94) but not non-Hispanic blacks (HR, 0.95; 95% CI, 0.73-1.25; P-interaction = 0.10). No statistically significant associations were observed for risk of breast or prostate cancers, overall or by race/ethnicity. Conclusions: No associations were observed for risk of overall cancer, breast cancer, or prostate cancer. While asthma was associated with increased lung cancer risk, history of allergies was associated with decreased risk, an association driven by an inverse association among non-Hispanic whites. Impact: Associations pertaining to lung cancer merit follow up in a large, diverse study.