Pre-diagnostic statin use, lymph node status and mortality in women with stages I-III breast cancer

Background: Recent meta-analyses suggest that pre-diagnostic statin use is associated with reduced breast cancer-specific mortality. Studies have shown that high breast tumour expression of the statin target (3-hydroxy-3-methylglutaryl coenzyme-A reductase) is associated with lymph-node negative cancer. Therefore, we examined the association between pre-diagnostic statin use and; lymph node status, breast cancer-specific and all-cause mortality. Methods: Women with stages I-III breast cancer were identified from the National Cancer Registry of Ireland (N = 6314). Pre-diagnostic statin users were identified from linked prescription claims data (N = 2082). Relative risks were estimated for associations between pre-diagnostic statin use and lymph node status. Hazard ratios (HR) were estimated for associations between pre-diagnostic statin use and breast cancer-specific and all-cause mortality. Results: Pre-diagnostic statin use was not associated with lymph node negative status at diagnosis. In multivariate analyses, pre-diagnostic statin use was associated with reduced all-cause (HR 0.78 95% confidence interval (CI) 0.69, 0.89) and breast cancer-specific mortality (HR 0.81 95% CI 0.68, 0.96). This reduction in cancer-specific mortality was greatest in statin-users with oestrogen (ER) receptor-positive tumours (HR 0.69 95% CI 0.55, 0.85). Conclusion: Patients with pre-diagnostic statin exposure had a significant reduction in breast cancer-specific mortality, which was even more pronounced in women with ER+ tumours.