Active cigarette smoking, household passive smoke exposure, and the risk of developing pancreatic cancer

Abstract

Objective

The objective of this study was to examine the association between active cigarette smoking, household passive smoke exposure, and pancreatic cancer risk using a prospective cohort design.

Methods

Two cohorts were established in Washington County, Maryland in 1963 (n = 45,749) and 1975 (n = 48,172). The Washington County Cancer Registry was used to ascertain the occurrence of pancreatic cancer in the 1963 cohort from 1963–1978 and in the 1975 cohort from 1975–1994. Poisson regression was used to analyze the associations between active smoking and household passive smoke exposure and pancreatic cancer risk.

Results

Current active smoking was associated with a two-fold increased risk of pancreatic cancer in both cohorts. Among never-smokers in each cohort, exposure to household passive smoke was not associated with an increased risk of pancreatic cancer, although the confidence limits were wide due to a small number of cases.

Conclusions

This study further documents the approximate doubling of pancreatic cancer risk in current active smokers. Our results also indicate that household passive smoke exposure is not associated with pancreatic cancer risk, although our risk estimates lacked precision.

Introduction

Pancreatic cancer causes 30,000 deaths per year in the United States, making it the fifth most common cause of cancer death (American Cancer Society, 2005). Although few risk factors for pancreatic cancer have been identified, epidemiological studies have consistently shown that cigarette smoking increases an individual's risk for pancreatic cancer (Ghadirian et al., 2003, U.S. Department of Health and Human Services (USDHHS), 2004, International Agency for Research on Cancer (IARC), 2004). In all, we identified nine prospective cohort studies examining the relationship between cigarette smoking and pancreatic cancer incidence using the Surgeon General's 2004 report (U.S. Department of Health and Human Services (USDHHS), 2004) and a MEDLINE search of the terms ‘smoking’ and ‘cancer’ (Engeland et al., 1996, Fuchs et al., 1996, Harnack et al., 1997, Nilsen and Vatten, 2000, Stolzenberg-Solomon et al., 2001, Isaksson et al., 2002, Lin et al., 2002, Jee et al., 2004, Larsson et al., 2005); the results of most of these studies indicate that cigarette smokers have a two- to three-fold increase in the risk of developing pancreatic cancer compared to non-smokers and that the risk of pancreatic cancer increases incrementally with the number of cigarettes smoked and the number of years smoked. Further, it has been estimated that smoking accounts for approximately one-fourth of pancreatic cancer incidence (Fryzek et al., 1997).

Cigarette smoking has consistently been reported to be a strong risk factor for pancreatic cancer, but additional data from large cohort studies are of value in enabling the association to be more thoroughly characterized and better understood. Furthermore, a paucity of literature exists examining the relationship between passive or secondhand smoke exposure and the risk of pancreatic cancer. Secondhand smoke contains many of the same toxic constituents as mainstream tobacco smoke, including 43 known carcinogens (Villeneuve et al., 2004, Brownson et al., 2002). Thus, it is biologically plausible that passive smoke exposure may be associated with the risk of developing pancreatic cancer. In a recently published case–control study, secondhand smoke exposure was not significantly associated with the risk of pancreatic cancer among 105 non-smoking pancreatic cancer cases and 1145 non-smoking population-based controls identified within 8 Canadian provinces (Villeneuve et al., 2004). No cohort studies addressing the association between passive smoke exposure and pancreatic cancer have been published. With this background in mind, we therefore conducted a community-based, prospective cohort study to investigate active and passive smoking in relation to the risk of developing pancreatic cancer.