Lipid-lowering drugs, dyslipidemia, and breast cancer risk in a Medicare population

Purpose We sought to disentangle the effects of statins and other lipid-lowering drugs and the underlying dyslipidemia for which they are prescribed on breast cancer risk. Methods We conducted a case–control study within the linked Surveillance, Epidemiology, and End results (SEER)-Medicare data. Cases were women with invasive breast cancer aged 66 + years ( N = 30,004) identified by SEER registries (years 2007–2011). Controls were women ( N = 198,969) identified from a 5% random sample of Medicare recipients alive and breast cancer free in year of selection. Participants had a minimum of 13 months of Part A, Part B non-health maintenance organization Medicare and Part D Medicare coverage at least 13 months preceding cancer diagnosis/selection. Exposures were assessed until 12 months before diagnosis/control selection. Odds ratios (OR) and 99.9% confidence intervals (CI) were estimated using adjusted unconditional and multinomial logistic regression. Results ORs of invasive breast cancer associated with dyslipidemia, statins, and non-statin lipid-lowering drugs were 0.86 (99.9% CI 0.81–0.90), 1.07 (99.9% CI 1.03–1.13) and 1.03 (99.9% CI 0.95–1.11), respectively. Risk reductions with dyslipidemia were slightly greater when untreated than treated and did not vary much by time between dyslipidemia and breast cancer diagnosis. Whether treated or untreated, dyslipidemia was associated with greater reductions in risk for later stage than earlier stage breast cancer ( p -heterogeneity < 0.0001). Conclusions Lipid-lowering drugs did not account for the lower breast cancer risk associated with dyslipidemia. Our data do not support using statins or other lipid-lowering drugs to prevent breast cancer.