Background:Studies examining associations between circulating concentrations of C-peptide and total adiponectin, two biomarkers related to obesity and insulin secretion and sensitivity and pancreatic ductal adenocarcinoma (PDA) risk have shown inconsistent results and included limited numbers of smokers. Methods:We examined associations of these biomarkers and high molecular weight (HMW) adiponectin with PDA, overall, and by smoking status. We conducted a pooled nested case-control analysis in 3 cohorts (Prostate, Lung, Colorectal, and Ovarian Cancer Trial, Alpha-Tocopherol, Beta-Carotene Cancer Prevention Study, and Cancer Prevention Study-II), with 758 cases (435 current smokers) and 1052 controls (531 smokers) matched by cohort, age, sex, race, blood draw date and follow-up time. We used conditional logistic regression adjusted for age, smoking, diabetes, and body mass index to calculate odds ratios (OR) and 95% confidence intervals (CI). Results:Circulating C-peptide concentration was not associated with PDA in never or former smokers, but was inversely associated with PDA in current smokers (per standard deviation OR=0.67, 95% CI 0.54, 0.84, p-interaction=0.005). HMW adiponectin was inversely associated with PDA in never smokers (OR=0.43, 95% CI 0.23, 0.81), not associated in former smokers, and positively associated in smokers (OR=1.23, 95% CI 1.04, 1.45, p-interaction=0.009). Total adiponectin was not associated with PDA in nonsmokers or current smokers. Conclusions:Associations of biomarkers of insulin secretion and sensitivity with PDA differ by smoking status. Smoking-induced pancreatic damage may explain the associations in smokers while mechanisms related to insulin resistance associations in non-smokers. Impact:Future studies of these biomarkers and PDA should examine results by smoking status.
- Received November 8, 2016.
- Revision received January 9, 2017.
- Accepted January 12, 2017.
- Copyright ©2017, American Association for Cancer Research.