A prospective study of cigarette smoking and the risk of pancreatic cancer.

OBJECTIVES To prospectively examine the excess incidence of pancreatic cancer among cigarette smokers and to examine the influence of smoking cessation on the risk of pancreatic cancer. METHODS We obtained data on cigarette smoking and other risk factors for pancreatic cancer from 118,339 women aged 30 to 55 years and 49,428 men aged 40 to 75 years who were without diagnosed cancer. During the 2,116,229 persons-years of follow-up, pancreatic cancer was diagnosed in 186 participants. RESULTS The multivariate relative risk of pancreatic cancer for current smokers was 2.5 (95% confidence interval, 1.7-3.6). A significant, positive trend in risk with increasing pack-years of smoking was observed (P for trend = .004), although this association was confined to cigarette consumption within the past 15 years. Compared with participants who continued to smoke, former smokers had a 48% reduction in pancreatic cancer risk within 2 years of quitting. Ultimately, the relative risk of pancreatic cancer among former smokers approached that for never smokers after less than 10 years of smoking cessation. Overall, the proportion of pancreatic cancers attributable to cigarette smoking was 25%. CONCLUSIONS Cigarette smoking is associated with an increased risk of pancreatic cancer. The rapid reduction in risk associated with quitting suggests that smoking cessation could eliminate 25% of the 27,000 deaths from pancreatic cancer occurring annually in the United States.