Cigarette smoking and risk of benign proliferative epithelial disorders of the breast in the Women's Health Initiative

Objective: To investigate the association between cigarette smoking and risk of benign proliferative epithelial disorders (BPED) of the breast. Methods: We used data from an ancillary study of benign breast disease that is being conducted in the Women's Health Initiative randomized clinical trials among 68,132 postmenopausal women aged 50-79 at recruitment. After following the trial participants for an average of 7.8 years, we had ascertained 294 incident cases with atypical hyperplasia and 1,498 incident cases with non-atypical BPED of the breast. We used Cox proportional hazards models to estimate hazard ratios for the association between cigarette smoking and risk of BPED. Results: Smoking measures, including duration of smoking, intensity of smoking, pack-years of smoking, age at which smoking commenced, and years since quitting smoking, were not associated with risk of BPED overall or by histological subtypes. Conclusion: The null association between cigarette smoking and risk of BPED of the breast suggests that the carcinogenic and antiestrogenic effects of cigarette smoking on the breast might counterbalance each other and that cigarette smoking might have no overall effects on BPED of the breast among postmenopausal women.