Smoking Cessation and Pancreatic Cancer Risk in Individuals With Prediabetes and Diabetes: A Nationwide Cohort Study

Background: Individuals with diabetes and prediabetes are at increased risk of pancreatic cancer. However, little is known about the effects of smoking or smoking cessation on pancreatic cancer risk in individuals with diabetes and prediabetes. We investigated the association between smoking status (particularly smoking cessation) and pancreatic cancer risk according to glycemic status. Patients and Methods: This nationwide cohort study included 9,520,629 adults without cancer who underwent the Korean National Health Screening in 2009 and were followed until 2018. Hazard ratios and 95% confidence intervals for pancreatic cancer were estimated after adjusting for potential confounders. Results: During the 78.4 million personyears of follow-up, 15,245 patients were newly diagnosed with pancreatic cancer. Among individuals with diabetes and prediabetes, current smoking synergistically increased pancreatic cancer risk (all P,.01). However, quitters with diabetes and prediabetes had a pancreatic cancer risk comparable to that of never-smokers (all P..05). For pancreatic cancer in current smokers, quitters, and never-smokers, respectively, the hazard ratios were 1.48 (95% CI, 1.40-1.58), 1.11 (95% CI, 1.03-1.19), and 1.00 (reference) among individuals with normoglycemia; 1.83 (95% CI, 1.70-1.97), 1.28 (95% CI, 1.18-1.39), and 1.20 (95% CI, 1.14-1.26) among individuals with prediabetes; and 2.72 (95% CI, 2.52-2.94), 1.78 (95% CI, 1.63-1.95), and 1.63 (95% CI, 1.54-1.72) among individuals with diabetes. There were no differences in risk between quitters with a,20 pack-year smoking history and never-smokers in all glycemic status groups. Conclusions: Pancreatic cancer risk synergistically increased in current smokers with diabetes and prediabetes. However, smoking cessation reduced the synergistically increased risk of pancreatic cancer to the level of never-smokers, especially when smoking history was,20 pack-years. More individualized and intensive cancer prevention education should be underscored for individuals at an increased risk of pancreatic cancer beyond the one-size-fits-all approach.