Plasma florescent oxidation products and breast cancer risk: repeated measures in the Nurses’ Health Study
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Reactive oxygen species (ROS), normally generated through biologic processes, may damage DNA, lipids, and proteins. ROS are balanced through enzymatic mechanisms and exogenous antioxidants; imbalance results in oxidative stress. Limited data suggest an association between oxidative stress and breast cancer. We evaluated pre-diagnostic plasma fluorescent oxidation products (FlOP), a global biomarker of oxidative stress, and breast cancer risk in a nested case–control study in the Nurses’ Health Study. Participants provided two blood samples (1989–1990 and 2000–2002) (N = 18,743). 377 women developed breast cancer between the second collection and June 1, 2006. Cases were matched to 377 controls. Relative fluorescent intensity at three different excitation/emission wavelengths (FlOP_360, FlOP_320, FlOP_400) were quantified in both samples, providing distant (≥10 years before diagnosis) and proximate (≤6 years before diagnosis) measures of oxidative stress. We observed no association between FlOP and breast cancer risk in proximate or distant samples (e.g., proximate extreme quartiles: FlOP_360, RR 0.8, 95 % CI 0.5–1.3, p trend = 0.49; FlOP_320, RR 1.1, 95 % CI 0.7–1.7, p trend = 0.53; FlOP_400, RR 1.3, 95 % CI 0.8–2.0, p trend = 0.80). In general no association was observed when cross-classifying or averaging proximate and distant exposure (e.g., extreme quartile of averages: FlOP_360, OR 0.9, 95 % CI 0.6–1.4, p trend = 0.82; FlOP_400, OR 0.9, 95 % CI 0.6–1.4, p trend = 0.55), with the exception of a significant trend for average FlOP_320 (extreme quartiles, OR 1.6, 95 % CI 1.0–2.4, p trend = 0.02). We did not observe important associations between FlOP and breast cancer risk in this large prospective study, though our data suggest women with consistently high FlOP_320 may be at increased risk.
KeywordsOxidative stress Breast cancer Fluorescent oxidation products
The authors would like to thank Susan Hankinson, Sc.D. for her important contributions to this manuscript. This work was funded by National Institute of Health Grants R01 CA131218, P01 CA87969, R01 CA49449. RT Fortner is supported in part by T32 CA09001. We would like to thank the participants and staff of the Nurses’ Health Study for their valuable contributions as well as the following state cancer registries for their help: AL, AZ, AR, CA, CO, CT, DE, FL, GA, ID, IL, IN, IA, KY, LA, ME, MD, MA, MI, NE, NH, NJ, NY, NC, ND, OH, OK, OR, PA, RI, SC, TN, TX, VA, WA, WY. In addition, this study was approved by the Connecticut Department of Public Health (DPH) Human Investigations Committee. Certain data used in this publication were obtained from the DPH. The authors assume full responsibility for analyses and interpretation of these data.
Conflict of interest
The authors declare no conflicts of interest.
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