No Association of Plasma Levels of Adiponectin and c-peptide with Risk of Aggressive Prostate Cancer in the Cancer Prevention Study II Nutrition Cohort

Background: Obesity is associated with a higher risk of aggressive prostate cancer and alters circulating levels of insulin and adiponectin, two hormones that influence biologic processes implicated in carcinogenesis. Results of some studies showed associations of circulating levels of adiponectin, insulin, and c-peptide (a marker of insulin secretion) with aggressive prostate cancer, but the size of these studies was limited. Methods: Anested case-control study of 272 aggressive prostate cancer cases [Gleason score >= 7 (4+3) or T3-T4] and 272 age-and race-matched controls from the Cancer Prevention Study II Nutrition Cohort was conducted to determine the associations of prediagnostic plasma levels of c-peptide and adiponectin with risk of aggressive prostate cancer. Results: Neither circulating adiponectin nor c-peptide was associated with risk of aggressive prostate cancer. In analyses of the highest-risk aggressive prostate cancer (Gleason score >= 8 or T3-T4), the highest quartile of c-peptide, compared with the lowest, was associated with an OR of 1.41 [ 95% confidence interval (CI), 0.72-2.78]. Conclusions: Our findings provide no support for the hypothesis that adiponectin is associated with risk of aggressive prostate cancer but a possible association of high levels of c-peptide with particularly high-risk prostate cancer cannot be ruled out. Impact: These results indicate that changes in circulating levels of adiponectin and c-peptide do not play an important role in risk of aggressive prostate cancer.