Cholesterol-lowering medication: Impact on the clinical effect of adjuvant endocrine treatment in postmenopausal breast cancer

Abstract

Background: Observational studies suggest that cholesterol-lowering medication (CLM) use is associated with longer recurrence-free survival in breast cancer patients. Since 2007, aromatase inhibitors (AIs) have been guideline treatment for estrogen receptor positive (ER+) postmenopausal breast cancer. AI therapy is associated with increased cholesterol levels. We investigated the association of CLM use and breast cancer recurrence rate in patients treated with AIs. Methods: This cohort included allwomen diagnosed with stage I-III ER+ breast cancer from2007-2016, treated with AI in the adjuvant setting, and registered in the Danish Breast Cancer Group database.We ascertained incident CLMexposure (≥1 prescription post-diagnosis) fromthe Danish National Prescription Registry andmodelledCLMas a time-varying exposure lagged by 6 months. Follow-up began 6 months after diagnosis and continued to the first event of recurrence, death, emigration, 10 years or 25th September 2018.We estimated recurrence rates, and crude and adjusted hazard ratios (HRs) with 95% confidence intervals (95% CI), comparing CLMexposure with non-exposure. Results: We enrolled 12,947 eligible patients. Median follow-up was 4.6 years. During follow-up, the total person-years of the unexposed group was 56,171 (incidence rate per 1,000 person-years: 11.50 [95% CI: 10.63-12.42]) and 5,246 in the CLM exposed group (incidence rate per 1,000 person-years: 12.20 [95% CI: 9.40-15.58]). There was little evidence of a protective effect of CLM on breast cancer recurrence during total follow-up but some evidence during the first 5 years (Table). Conclusions: CLM use was not associated with a substantially reduced risk of breast cancer recurrence among AI users. (Table Presented) .