Urinary 8-isoprostane levels and occurrence of lung, colorectal, prostate, breast and overall cancer: Results from a large, population-based cohort study with 14 years of follow-up.

Background Urinary 8‐isoprostane is an established biomarker for lipid peroxidation. However, the association between its pre-diagnostic levels and cancer incidence has rarely been evaluated. Methods 8793 older adults from the German ESTHER cohort were followed up for cancer incidence by cancer registry data. A directed acyclic graph was utilized to identify potential confounders. Multivariate Cox regression models were applied to estimate hazard ratios (HRs) and 95% confidence intervals (95% CI). Results During 14-year follow-up, 1540 incident cancer cases, including 207 lung, 196 colorectal, 218 breast and 245 prostate cancer cases were detected. 8-isoprostane concentrations were positively associated with lung cancer, but not with cancer at the other sites. The HR (95% CI) for the association with lung cancer was 1.61 (1.10, 2.34) for comparison of the top with bottom tertile in total population. The association of 8-isoprostane levels with lung cancer persisted after the adjustment for smoking and other potential confounders and was multiplicative to the effect of smoking. However, 8-isoprostane levels did not improve lung cancer prediction when added to a model containing age, sex and smoking. A protective association of increasing 8-isoprostane levels was observed for prostate cancer incidence but this association was only statistically significant among current smokers. Discussion Our findings suggest that lipid peroxidation is involved in the development of lung cancer. However, high oxidative stress may be a protective factor for prostate cancer, especially among current smokers. [ABSTRACT FROM AUTHOR]