IL6 and breast cancer: The aim of this prospective observational study was to examine in a population of post-menopausal breast cancer patients the correlations between traditional prognostic factors, and BMI, leptin, circulating levels of pro-inflammatory cytokines (IL-6, TNF-α), and oxidative stress (reactive oxygen species, ROS, glutathione peroxidase, GPx, superoxide dismutase, SOD).