Abstract 4813: The increased risk of colon cancer due to cigarette smoking may be greater in women than men.

Abstract

Abstract Background: The International Agency for Research on Cancer (IARC) has recently established cigarette smoking as a risk factor for colon cancer. Norway has one of the highest incidence rates of colon cancer in the world especially among women. We examined the association between different measures of smoking exposure and colon cancer by gender in a large Norwegian cohort. Methods: We followed 602,242 participants aged 19-67 years at enrollment who completed a questionnaire in 1972-2003, by linkage to national registries through December 2007. We used Cox proportional hazard regression models to estimate hazard ratios (HR) and 95% confidence intervals (CIs) adjusting for age, body mass index, physical activity and education. Results: During a mean follow-up time of 14 years, 2,152 men and 1,846 women developed colon cancer. Women ever smokers had a 19% increased risk (HR=1.19, 95% CI=1.09-1.32) and men ever smokers had an 8% increased risk (HR=1.08, 95% CI=0.97-1.19) compared with never smokers. The association was more consistent for proximal than distal colon cancer among women ever smokers. The dose-response association between latency, number of years smoked, number of cigarettes per/day, number of pack-years and colon cancer risk among women was stronger than in men. Test for heterogeneity of the smoking effect between men and women was significant among ever smokers only for proximal colon cancer (Wald p=0.02). Conclusions: The results provide further evidence that smoking plays a role in the etiology of colon cancer. Female smokers may be more susceptible to proximal colon cancer than male smokers. Citation Format: Ranjan Parajuli, Eivind Bjerkaas, Aage Tverdal, Randi Selmer, Loic Le Marchand, Elisabete Weiderpass, Inger Torhild Gram. The increased risk of colon cancer due to cigarette smoking may be greater in women than men. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 4813. doi:10.1158/1538-7445.AM2013-4813