Abstract B87: Cigarette smoking, lifetime exposure to passive smoking, and the risk of non-Hodgkin lymphoma in the California Teachers Study

Abstract

Abstract Background: Overall, epidemiological studies conducted to date do not support a causal relationship between smoking and non-Hodgkin lymphoma (NHL) risk. However, previous studies did not account for passive smoking in the referent group of never smokers, which may have masked subtle effects. We therefore examined the effects of cigarette smoking and passive smoking on NHL risk in the prospective California Teachers Study (CTS) cohort. Methods: The CTS collected lifetime smoking and household passive smoking exposures in 1995 and lifetime passive smoking exposures in three settings (household, workplace, and social) in 1997-1998. Multivariable-adjusted relative risks (RRs) and 95% confidence intervals (CI) were estimated by fitting Cox proportional hazards models for NHL risk with follow-up through 2007. Results: Compared to never smokers, ever smokers had a 1.11-fold elevated NHL risk (95% CI=0.94-1.30) which increased to 1.22 (95% CI=0.95-1.57) when women with household passive smoking were excluded from the reference category. Statistically significant dose-response trends were observed for lifetime cumulative smoking exposures (intensity and pack-years) when women with household passive smoking were excluded from the reference category (both p-trend=0.02). Among never smokers, NHL risk increased with increasing lifetime passive smoking exposure [RR=1.51 (95% CI=1.03-2.22) for more than 40 vs. less than or equal to 5 years, p-trend=0.03]. Both smoking and passive smoking were associated with increased risk of follicular lymphoma, but not other NHL subtypes. Conclusion: Our study provides evidence that smoking and passive smoking may play a role in NHL etiology, particularly for follicular lymphoma. Studies evaluating the effect of smoking should consider the effects of passive smoking. Citation Information: Cancer Prev Res 2010;3(12 Suppl):B87.