Abstract
Interleukinβ6 (ILβ6) and Cβreactive protein (CRP) are elevated in prostate cancer patients, but the role of prediagnostic levels of these inflammatory mediators on prostate cancer outcomes is unclear. We undertook a large, prospective caseβcontrol study to evaluate the relation between prediagnostic levels of ILβ6 and CRP and prostate cancer incidence and mortality. We also investigated the role of the ILβ6 (β174 G/C) polymorphism in relation to circulating levels of ILβ6 and CRP, as well as cancer risk and mortality. We used unconditional logistic regression that adjusted for matching factors to analyze prostate cancer risk. For analyses of prostate cancer mortality, we conducted survival analyses in cases. Because of the strong link between inflammatory markers and body mass index (BMI), we assessed interactions between BMI and plasma levels on prostate cancer outcomes. Neither ILβ6 nor CRP plasma levels varied significantly by ILβ6 genotype. Genotype was not associated with prostate cancer risk or survival. Though neither ILβ6 nor CRP was associated with prostate cancer incidence overall, we observed a statistically significant interaction between ILβ6 and BMI on prostate cancer incidence (p~interaction~ < 0.01). Increasing ILβ6 levels were positively associated with risk in healthy weight men, but inversely associated with risk in overweight men. Further, prediagnostic ILβ6 was associated with time to prostate cancer progression/death among healthy weight prostate cancer cases (p~trend~ = 0.02). Adjusted hazard ratios were 1.73 (95% CI: 0.86, 3.51) comparing the highest to lowest ILβ6 level. Our study suggests that ILβ6 may potentially be involved in the development or progression of prostate cancer. Β© 2008 WileyβLiss, Inc.