Abstract 1831: Cigarette smoking and risk of epithelial ovarian cancer according to histological subtypes: results from the EPIC study
Authors: Gram Inger T. , Braaten Tonje , Brill Ilene , Lund Eiliv , Dossus Laure , Kaaks Rudolf , Lukanova Annekatrin , Lundin Eva 
Published: February 2011

Abstract
Objective: Studies regarding the association between smoking and risk of epithelial ovarian cancer (EOC) are few and inconsistent. The purpose of this study was to examine the association between smoking and subtypes of EOC in the EPIC cohort.
Material and methods : The EPIC cohort is a large, multi-centre prospective study to investigate the relations of nutritional, lifestyle, metabolic and genetic risk factors and cancer incidence. It was initiated in 1992 in ten European countries (Sweden, Denmark, Norway, the Netherlands, United Kingdom, France, Germany, Spain, Italy and Greece). The questionnaires included data about dietary, lifestyle and health factors. Information about tobacco smoking was collected from individuals in all participating countries. Subjects were asked if they smoked cigarettes currently and whether they had smoked in the past. Information was available on current and life-time number of cigarettes per day, duration of smoking, age started smoking and age of smoking cessation (for former smokers). Incident cancer cases were identified through several methods, including record linkage with regional cancer registries, health insurance records, cancer and pathology registries and active follow-up of study subjects. We used Cox proportional hazard regression models to estimate hazard ratio (RR) of EOC with 95% confidence intervals (CIs) associated with different measures of smoking exposures adjusting for confounding variables and stratifying by center.
Results: Altogether 836 [731 (87%) invasive, 67(8%) borderline and 38(5%) unclassified] incident EOC cases were identified among the 326,788 women during an average of 6 years of follow-up. The tumours were classified as 400 serous, 83 mucinous, 80 endometroid and 35 clear cell and 238 unspecified. Altogether, 11% of the serous and 28% of the mucinous tumors was classified as borderline tumors. Twenty-three percent of the women reported to be former and 20% current smokers. The multivariate models showed that current smokers had a 10 % increased risk for EOC overall [RR=1.1(95 % CI 0.9 − 1.4)], a 70% increased risk of borderline tumors [RR=1.7(95 % CI 0.9 − 3.0) and an 80 % [RR=1.8(95 % CI 1.1 − 3.0)] increased risk of mucinous tumors. Only the latter association achieved statistical significance. A positive trend test for age started smoking (&lt;17,17-19,20+, never) and risk of EOC overall (P=0.03) was found among ever smokers who had smoked at least 20 years.
Conclusion: Our results support the notion that smoking increases the risk of mucinous EOC.
Note: This abstract was not presented at the AACR 101st Annual Meeting 2010 because the presenter was unable to attend.
Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 1831.