Environmental tobacco smoke and the risk of pancreatic cancer among non-smokers: a meta-analysis

Background Experimental studies have linked exposure to tobacco-specific nitrosamines with pancreatic carcinogenesis. A number of epidemiological studies have examined the association between environmental tobacco smoke (ETS) and risk of pancreatic cancer but they have not yet been jointly summarised. Objectives To investigate the association between exposure to ETS and risk of pancreatic cancer by systematically reviewing and synthesising the available evidence. Methods We conducted a comprehensive literature search using MEDLINE and EMBASE and manual searching of the reference lists of the relevant research reports and review articles to identify full texts and abstracts published through October 2011. We used the random-effects model to pool summary relative risks (RR) comparing the highest category of exposure to ETS to people who had never been exposed. Results Exposure to ETS during childhood was not associated with risk of pancreatic cancer (three prospective and two retrospective studies; summary RR 1.12; 95% CI 0.89 to 1.43). In addition, no association was found with exposure to ETS during adulthood at home (five prospective and three retrospective studies; summary RR 1.23; 95% CI 0.86 to 1.77) or at work (one prospective and two retrospective studies; summary RR 0.94; 95% CI 0.67 to 1.33). Conclusions This meta-analysis does not provide evidence for an association between exposure to ETS and risk of pancreatic cancer.