Low-grade inflammation, oxidative stress and risk of invasive post-menopausal breast cancer - A nested case-control study from the Malmö 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 31^st, 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)- 1β, IL-6, IL-8, tumor necrosis factor (TNF)-α, 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 2^nd and 3^rd 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 3^rd tertile of TNF-α, 0.65 (0.43.0.99), p-trend = 0.04. In contrast, those in the highest IL-1β 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.