Low-Grade Inflammation, Oxidative Stress and Risk of Invasive Post-Menopausal Breast Cancer - A Nested Case-Control Study from the Malmo Diet and Cancer Cohort

Objective Although cancer promotes inflammation, the role of inflammation in tumor-genesis is less well established. The aim was to examine if low-grade inflammation is related to post-menopausal breast cancer risk, and if obesity modifies this association. Methods In the Malmo Diet and Cancer cohort, a nested case-control study was defined among 8,513 women free of cancer and aged 55-73 years at baseline (1991-96); 459 were diagnosed with invasive breast cancer during follow-up (until December 31st, 2010). In laboratory analyses of blood from 446 cases, and 885 controls (matched on age and date of blood sampling) we examined systemic inflammation markers: oxidized (ox)-LDL, interleukin (IL)-1 beta, IL-6, IL-8, tumor necrosis factor (TNF)-alpha, white blood cells, lymphocytes and neutrophils. Odds ratios (OR) and 95% confidence intervals (CI) for breast cancer risk was calculated using multivariable conditional logistic regression. Results Inverse associations with breast cancer were seen in fully-adjusted models, for 2nd and 3rd tertiles of ox-LDL, OR (95% CI): 0.65 (0.47-0.90), 0.63 (0.45-0.89) respectively, p-trend = 0.01; and for the 3rd tertile of TNF-alpha, 0.65 (0.43-0.99), p-trend = 0.04. In contrast, those in the highest IL-1 beta category had higher risk, 1.71 (1.05-2.79), p-trend = 0.01. Obesity did not modify associations between inflammation biomarkers and breast cancer. Conclusion Our study does not suggest that low-grade inflammation increase the risk of post-menopausal breast cancer.