Inflammatory biomarkers and risk of postmenopausal oestrogen receptor-positive breast cancer: a case-cohort analysis.

BACKGROUND: The role of systemic inflammation in postmenopausal breast carcinogenesis remains unclear. Using a case-cohort study within the Melbourne Collaborative Cohort Study, we estimated the effects of circulating inflammatory biomarkers on the risk of postmenopausal oestrogen receptor (ER)-positive breast cancer. METHODS: We included 1223 females (347 cases) who were postmenopausal at blood collection. For each biomarker, risk ratios (RRs) and 95% confidence intervals (CIs) for ER-positive breast cancer were estimated (1) per-doubling in biomarker concentration and (2) for quartiles of concentration with the lowest category as the reference, using weighted Poisson regression with a robust variance estimator. RESULTS: The risk of postmenopausal ER-positive breast cancer increased per doubling in blood concentrations of leptin (RR: 1.13, 95% CI: 1.03, 1.25), adiponectin (RR: 1.10, 95% CI: 0.90, 1.34), tumour necrosis factor-alpha (RR: 1.27, 95% CI: 0.96, 1.68), and interleukin-10 (RR: 1.14, 95% CI: 1.01, 1.29). The RR for a doubling of the leptin-to-adiponectin ratio was 1.07 (0.99, 1.16). RRs for other biomarkers were 1.04 (0.93, 1.17) for interferon-gamma, 1.01 (0.88, 1.17) for interleukin-6, 0.98 (0.83, 1.16) for interleukin-8, and 1.03 (0.95, 1.11) for C-reactive protein. CONCLUSION: Systemic inflammation may be important in the risk of developing ER-positive breast cancer for postmenopausal females.