Statin use and risks of breast cancer recurrence and mortality

Abstract Background Preclinical evidence suggests improved breast cancer survival associated with statin use, but findings from observational studies are conflicting and remain inconclusive. The objective of this study was to assess the association between statin use after cancer diagnosis and cancer outcomes among breast cancer patients. Methods In this retrospective cohort study, 38,858 women aged ≥66 years who were diagnosed with localized and regional stage breast cancer from 2008 through 2017 were identified from the linked Surveillance, Epidemiology, and End Results Medicare database. Statin use was ascertained from Medicare Part D pharmacy claims data. Multivariable Cox proportional hazards models were used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) for the association between post‐diagnosis statin use and risks of breast cancer recurrence and breast cancer–specific mortality. Results Over a median follow‐up of 2.9 years for recurrence and 3.7 years for mortality, 1446 women experienced a recurrence, and 2215 died from breast cancer. The mean duration of post‐diagnosis statin use was 2.2 years. Statin use post‐diagnosis was not associated with recurrence risk (HR, 1.05; 95% CI, 0.91–1.21), but was associated with a reduced risk of cancer‐specific mortality (HR, 0.85; 95% CI, 0.75–0.96). The reduction was more pronounced in women with hormone receptor–positive/human epidermal growth factor receptor 2–negative breast cancer (HR, 0.71; 95% CI, 0.57–0.88). Conclusions These findings suggest that post‐diagnosis statin use is associated with improved cancer‐specific survival in women with breast cancer and should be confirmed in randomized trials of statin therapy in breast cancer patients.