Abstract
Breast cancer tends to arise in older women who are also burdened with comorbidities such as cardiovascular disease (CVD). Increasing numbers of breast cancer survivors and an aging population warrant a better understanding of CVD management and adherence to preventive therapies. We estimated adherence to statins and therapeutic goal lipid values during the year before breast cancer diagnosis or baseline, treatment period, and in subsequent years of clinical management among breast cancer survivors. We sampled women from an existing cohort of 4,221 women diagnosed with incident early stage (I, II) invasive breast cancer from 1990 to 2008 and enrolled in a large integrated group practice health plan. Among prevalent statin users (N = 1,393), medication adherence and persistence were measured by medication possession ratio (MPR), % adherent (MPR < 0.80), and discontinuation rates. Laboratory data on LDL and HDL were obtained for the coinciding periods. Mean MPR for statin use (0.78 vs. 0.68; P < 0.001) and proportion adherent (67.0 vs. 51.9 %; P < 0.001) declined from baseline to the treatment period. Mean LDL (143 mg/dL baseline vs. 150 mg/dL treatment period; P < 0.001) and proportion not at LDL goal (60.1 vs. 70.8 %; P < 0.001) coincided with decreases in adherence. During treatment, non-adherent statin users had the highest mean LDL (160.4 mg/dL) and proportion not at goal LDL (91.8 %) overall. Adherence did not return to baseline in subsequent years following treatment although LDL levels did. HDL did not differ by periods of interest or adherence levels. Adherence to statins in this population was poor, particularly in the treatment period, and lagged in returning to baseline. Understanding the influence of life events such as cancer diagnosis and treatment on management of comorbidities and adherence to preventive therapies are important to the growing population of breast cancer survivors.