Purpose: To evaluate the association between statins and breast cancer stage and mortality in the Women's Health Initiative.
Methods: The study population included 128,675 postmenopausal women aged 50-79 years, out of which there were 7,883 newly diagnosed cases of in situ (19%), local (61%)-, regional (19%)- and distant (1%)-stage breast cancer and 401 deaths due to breast cancer after an average of 11.5 (SD = 3.7) years of follow-up. Stage was coded using SEER criteria and was stratified into early (in situ and local)- versus late (regional and distant)-stage disease. Information on statins and other risk factors were collected by self- and interviewer-administered questionnaires. Cause of death was based on medical record review. Multivariable-adjusted hazards ratios (HR) and 95% confidence intervals (CIs) evaluating the relationship between statin use (at baseline only and in a time-dependent manner) and diagnosis of late-stage breast cancer and breast cancer-specific mortality were computed from Cox proportional hazards analyses after adjusting for appropriate confounders.
Results: Statins were used by 10,474 women (8%) at baseline. In the multivariable-adjusted time-dependent model, use of lipophilic statins was associated with a reduction in diagnosis of late-stage breast cancer (HR 0.80, 95% CI 0.64-0.98, p = 0.035) which was also significant among women with estrogen receptor-positive disease (HR 0.72, 95% CI 0.56-0.93, p = 0.012). Breast cancer mortality was marginally lower in statin users compared with nonusers (HR 0.59, 95 % CI 0.32-1.06, p = 0.075).
Conclusions: Prior statin use is associated with lower breast cancer stage at diagnosis.