Statin Use and Breast Cancer Risk in the Nurses' Health Study.

Preclinical studies support an anticancer effect of statin drugs, yet epidemiologic evidence remains inconsistent regarding their role in breast cancer primary prevention. Here, we report an updated analysis of the association between statin use and breast cancer incidence in the Nurses' Health Study (NHS) cohort. Postmenopausal NHS participants without a cancer history were followed from 2000 until 2012 (n = 79,518). Data on statin use were retrieved from biennial questionnaires. We fit Cox regression models to estimate associations between longitudinal statin use and breast cancer incidence. Over 823,086 person-years of follow-up, 3,055 cases of invasive breast cancer occurred. Compared with never users, both former and current statin users had similar rates of invasive breast cancer incidence [former users: HRadj, 0.96; 95% confidence interval (CI), 0.82-1.1; current users: HRadj, 1.1; 95% CI, 0.92-1.3]. Associations did not differ by estrogen receptor (ER) status or histology (ductal vs. lobular carcinoma). Statin use was not associated with risk of invasive breast cancer, irrespective of histologic subtype and ER status. Statin drugs do not appear to modify processes involved in breast cancer initiation.