Hormonal risk factors for endometrial cancer: modification by cigarette smoking (United States)

Objectives: To evaluate whether smoking modifies the risk of endometrial cancer associated with body mass index (BMI), postmenopausal hormone use, and other hormonal factors. Methods: Using multivariate adjusted models we examined interview data from a population-based case-control study of Wisconsin women (n = 740 cases, n = 2372 controls). Results: The relative risk for endometrial cancer associated with current smoking was 0.8 (95% CI: 0.6-1.0) compared to never smokers. No clear dose-response relationship was evident for pack-years smoked. When examined according to smoking status the risk associated with the highest quartile of BMI seemed to be greater among non-smokers (OR = 3.6, 95% CI: 2.4-5.3) than among current smokers (OR = 2.8, 95% CI: 1.4-5.6). Among postmenopausal women the risk associated with current use of postmenopausal hormones appeared to be greater among non-smokers (OR = 3.3, 95% CI: 2.3-4.9) than among current smokers (OR = 2.7, 95% CI: 1.3-5.5). Risk for long-term use (10 or more years) compared with never users was 8.3 (95% CI: 4.6-15.1) among never smokers and 2.5 (95% CI: 0.8-7.9) among current smokers. The risk associated with non-insulin-dependent diabetes was greater among non-smokers (OR = 2.5, 95% CI: 1.7-3.6) than current smokers (OR = 1.1, 95% CI: 0.4-3.1). There was no modifying effect of smoking on the risk associated with parity. Conclusion: These results suggest that smoking moderates the risk associated with endometrial cancer among women at greatest risk, specifically women who are obese or who use postmenopausal hormones.