ociation between C-Peptide Concentration and Prostate

r Prev Res betes, characterized by perturbations in insulin production and signaling, is inversely associated rostate cancer risk irrespective of stage. Obesity, a diabetes risk factor, is inversely associated with ed disease but positively associated with advanced disease. To understand the complex associaetween hyperinsulinemia and prostate cancer, we evaluated the association of plasma C-peptide, ulin secretion marker, with prostate cancer risk in a case-control study nested in a prospective unity cohort. Prostate cancer cases (n = 264) and matched controls (n = 264) were identified CLUE II cohort between 1989 (baseline) and 2002. C-peptide concentration was measured in ne plasma by ELISA. Odds ratios (OR) and 95% confidence intervals (95% CI) were estimated conditional logistic regression, adjusting for being overweight or obese and family history. n C-peptide concentration was lower in cases (1,180 pmol/L) than in controls (1,365 pmol/L; .03). Men in the highest (versus lowest) fourth of C-peptide had a lower risk for prostate cancer .65; 95% CI, 0.37-1.14; P-trend = 0.08), primarily localized disease (OR, 0.44; 95% CI, 0.19-1.03; d = 0.04). Associations were similar to overall, when excluding cases diagnosed during the first rs of follow-up, men with diabetes, or men who had not had a prostate-specific antigen test. tide concentration was inversely associated with subsequent diagnosis of prostate cancer, primarily ed disease, similar to the association for obesity. However, we cannot rule out detection bias that localiz might result if men with higher C-peptide have lower prostate-specific antigen irrespective of whether prostate cancer is present or not. Cancer Prev Res; 3(10); 1334–41. ©2010 AACR.