Abstract PD03-09: Statins and breast cancer risk: A follow-up analysis of the Women's Health Initiative Cohort
Authors: Desai P , Jay A , Wu C , Cauley JA , Manson J , Peters U , Agalliu I , Abdul-Hussein M , Bock C , Budrys N , Chlebowski R , Cote M , Lane D , Luo J , Martin L , Park H , Petrucelli N , Rosenberg CA , Thomas F , Wactawski-Wende J , Simon MS 
Published: August 2014

Introduction: Statins (HMG CoA reductase inhibitors) are a class of cholesterol lowering drugs that affect many intracellular pathways and have implications for chemopreventive activity against cancer. Epidemiological data on statins and breast cancer risk are conflicting. We analyzed updated data from the Women's Health Initiative (WHI) to assess the relationship between statins and breast cancer risk.

Methods: This analysis included 154,587 post-menopausal women ages 50–79 years at baseline, in which 7,430 incident cases of invasive breast cancer were identified over an average of 10.8 (SD 3.3) years of follow-up. All cases of breast cancer were confirmed by review of medical records and pathology reports. Participants were asked to bring all current medications to their baseline visits and information on statin use was recorded. Statins were classified as lipophilic (lovastatin, simvastatin, fluvastatin) or hydrophilic (pravastatin and atorvastatin). Self and interviewer-administered questionnaires were used to collect information on other breast cancer risk factors. Cox proportional hazards regression was used to calculate hazard ratios (HRs) with 95% confidence intervals (CIs). Analyses investigated the association of any statin use as well as, type of statin (lipophilic vs. hydrophilic), statin potency, and duration of use with breast cancer. To evaluate the effect of change in statin use over time, statin use was examined as a time-dependent exposure using updated information on statin use gathered during follow-up visits. Separate analyses were conducted by hormone receptor and HER2neu status, other tumor characteristics and use of postmenopausal hormone therapy. All statistical tests were two-sided.

Results: Statins were used at baseline by 11,584 (7.5%) women in the cohort of whom 7,840 used lipophilic statins. The annualized rate of breast cancer was 0.42% among statin users and 0.42% among nonusers. The multivariable adjusted HR of breast cancer for statin users compared with non-users was 0.93 (95% C.I. 0.83–1.05), however for women using lipophilic statins the HR was 0.86 (95% CI, 0.74–1.00). Statin use for &lt; 1 year was associated with a reduction in risk (HR 0.79, 95% C.I. 0.63–0.99) however there was no trend for overall duration of use. In the stratified analysis by tumor size, there was a marginal reduction in risk for tumors between 10 and 30 mm but not in smaller or larger tumors. There were no effect modifications by tumor stage, hormone receptor or HER2neu status, hormone therapy use, family history of breast cancer or body mass index. In the multivariable adjusted time-dependent model, the HR for simvastatin was 0.80 (95% CI, 0.64–0.99).

Conclusion: Simvastatin was associated with a reduced risk of invasive breast cancer, and as a class, lipophilic statins were associated with a marginal benefit. This provides further evidence for possible class differences in statins with regard to chemo-preventive effects in breast cancer.

Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr PD03-09.