IL6 and cancer: Considerable evidence, including work by our group, suggests that HRQOL impairments in cancer survivors are causally linked to changes in stress-related physiological function, including diurnal cortisol production and biomarkers of inflammation (plasma interleukin (IL)-1β, IL-6, and tumor necrosis factor (TNF)-α; peripheral blood mononuclear cell (PBMC) nuclear factor-κB (NF-κB)) [37, 38].