Association between nonadherence to cardiovascular risk factor medications after breast cancer diagnosis and incidence of cardiac events.

BACKGROUND: Cardiovascular disease (CVD) is the leading cause of death among patients with early-stage breast cancer (BC), but adherence to cardiovascular disease risk factor (CVD-RF) medications is reported to be poor in BC survivors. The objective of the current study was to determine the association between nonadherence to CVD-RF medications and cardiovascular events in BC survivors. METHODS: The authors included patients with stages I to III BC from the Surveillance, Epidemiology, and End Results (SEER)-Medicare database who had Medicare part D coverage and who were taking at least 1 CVD-RF medication prior to their BC diagnosis (2008-2013). Logistic regression was performed to define factors associated with nonadherence. Cox regression was used to calculate the association between nonadherence and new cardiac events after treatment. RESULTS: Among 15,576 patients included in the current analysis, 4797 (30.8%) were nonadherent to at least 1 category after the initial BC treatment period. Black race, greater comorbidity burden, more advanced cancer stage, hormone receptor-negative status, and receipt of chemotherapy were found to be associated with nonadherence. Nonadherence after treatment demonstrated a trend toward an increased risk of a subsequent cardiac event (hazard ratio [HR], 1.15; 95% CI 1.00-1.33 [P = .06]). This effect size increased with nonadherence to a greater number of medications (P < .01). There was an increased risk of experiencing a cardiac event noted with becoming nonadherent to hypertension medications (HR, 1.33; 95% CI, 1.18-1.51 [P < .0001]), hyperlipidemia medications (HR, 1.21; 95% CI, 1.05-1.40 [P = .009]), and diabetes medications (HR, 1.31; 95% CI, 1.10-1.56 [P = .003]). CONCLUSIONS: Nonadherence to CVD-RF medications after treatment of BC is associated with an increased risk of a cardiac event. Improving outcomes and reducing morbidity after a diagnosis of BC requires attention to non-BC conditions.