Peripheral blood eosinophil counts and risk of colorectal cancer mortality in a large general population-based cohort study

1583 Background: Few epidemiological studies have investigated the association between blood eosinophil counts and colorectal cancer incidence. The current prospective cohort study aims to investigate the association between peripheral blood eosinophils and colorectal cancer mortality risk.

METHODS: Vital status at December 31(st), 2008 of 8465 participants of the Vlagtwedde/Vlaardingen (a rural respectively industrial area in The Netherlands) cohort study was determined. This study started in 1965 and participants had medical examinations every 3 years until the last survey in 1989/1990. Blood eosinophil counts at the first survey were logtransformed to obtain a normal distribution. Multivariate Cox regression analyses on colorectal cancer mortality in the total population with adjustment for age, FEV1 % predicted, BMI, smoking habit, gender and place of residence, were performed. Furthermore, stratified analyses by smoking habits (never versus ever) and by gender were performed. Finally, interactions between eosinophil counts and smoking habits, respectively gender were investigated.

RESULTS: In total, 3838 subjects had died; 134 died due to colorectal cancer. There was no association between eosinophil counts and colorectal cancer mortality risk in the total population (Hazard Ratio (95% CI) == 0.84 (0.65-1.09)). The stratified analyses showed significant associations between number of eosinophils and colorectal cancer mortality in males (HR== 0.64 (95% CI 0.45-0.89)) and in ever smokers (HR== 0.63 (95% CI 0.46-0.86)). Additionally, we observed a significant interaction between male gender and eosinophil counts (HR== 0.48 (95% CI 0.28-0.80)) and between smoking and eosinophil counts on colorectal cancer mortality (HR== 0.40 (95% CI 0.23-0.70)).

CONCLUSIONS: A higher number of peripheral blood eosinophils is associated with a reduced risk to die of colorectal cancer, especially in ever smokers and in males. Although the underlying mechanism explaining this observation is not clear, it suggests that a more active immune system reduces the risk to develop colorectal cancer.