Statin use in patients with hormone receptor‐positive metastatic breast cancer treated with everolimus and exemestane

BACKGROUND: We analyzed the effect of statins in patients with hormone receptor‐positive (HR+) metastatic breast cancer treated with everolimus + exemestane (EverX). MATERIALS AND METHODS: We conducted a nationwide retrospective cohort study using the National Health Insurance database with patients who received EverX for metastatic breast cancer between 2011 and 2019. RESULTS: Of 224,948 patients diagnosed with breast cancer, 1749 patients who received EverX for at least 30 days were included. Among them, 500 (28.6%) patients were found to take statins with EverX treatment (statin group), and the median duration of this combination was 5.36 months. The median time to treatment duration (TTD) for EverX and the overall survival (OS) were significantly higher in the statin group than in the no‐statin group [7.69 vs. 5.06 months, p < 0.001; 45.7 vs. 26.0 months, p < 0.001, respectively]. Multivariable Cox analysis revealed that the use of statins was associated with prolonged TTD [HR = 0.67 (95% CI, 0.59–0.77)] and OS [HR = 0.57 (95% CI, 0.46–0.70)] for EverX even after adjustment for other covariates. CONCLUSION: Statins may have synergistic effects with endocrine therapy with the mTOR inhibitor everolimus, and improve survival in patients with HR+ metastatic breast cancer.