Pancreatic cancer: associations of inflammatory potential of diet, cigarette smoking and long-standing diabetes

Abstract

Epidemiologic studies show strong associations between pancreatic cancer (PC) and inflammatory stimuli or conditions such as cigarette smoking and diabetes, suggesting that inflammation may play a key role in PC. Studies of dietary patterns and cancer outcomes also suggest that diet might influence an individual's risk of PC by modulating inflammation. We therefore examined independent and joint associations between inflammatory potential of diet, cigarette smoking and long-standing (≥5 years) type II diabetes in relation to risk of PC. Analyses included data from 817 cases and 1756 controls. Inflammatory potential of diet was measured using the dietary inflammatory index (DII), calculated from dietary intake assessed via a 144-item food frequency questionnaire, and adjusted for energy intake. Information on smoking and diabetes were obtained via risk factor questionnaires. Associations were examined using multivariable-adjusted logistic regression. Higher DII scores, reflecting a more proinflammatory diet, were associated with increased risk of PC [odds ratio (OR)Quintile 5 versus 1 = 2.54, 95% confidence interval (CI) = 1.87-3.46, P trend < 0.0001]. Excess risk of PC also was observed among former (OR = 1.29, 95% CI = 1.07-1.54) and current (OR = 3.40, 95% CI = 2.28-5.07) smokers compared with never smokers, and among participants with long-standing diabetes (OR = 3.09, 95% CI = 2.02-4.72) compared with nondiabetics. Joint associations were observed for the combined effects of having greater than median DII score, and being a current smoker (OR = 4.79, 95% CI = 3.00-7.65) or having long-standing diabetes (OR = 6.03, 95% CI = 3.41-10.85). These findings suggest that a proinflammatory diet may act as cofactor with cigarette smoking and diabetes to increase risk of PC beyond the risk of any of these factors alone.