Abstract PD6-10: Association between adherence to cardiovascular medications and cardiovascular events following a diagnosis of early stage breast cancer
Authors: Hershman DL , Accordino M , Shen S , Buono D , Crew KD , Kalinsky K , Trivedi MS , Unger JM , Wright JD 
Published: May 2019

Background: Studies show that patients diagnosed with early-stage breast cancer (BC) are more likely to die from cardiovascular disease (CVD) than BC. Adherence to CVD medications, such as statins and antihypertensives, is poor in BC survivors, particularly in the year following diagnosis. The impact of non-adherence to CVD medications on cardiovascular events in BC survivors is unknown.

Methods: Using the Surveillance, Epidemiology, and End Results (SEER)-Medicare linked dataset, we evaluated patients with non-metastatic BC who were diagnosed between 2006-2014. Prescriptions were identified for the treatment of hypertension, hyperlipidemia and diabetes. The pre-cancer diagnosis study period for adherence was defined as 1 year prior to the diagnosis of cancer. The follow up adherence period was between years 1 and 2 following the diagnosis of cancer, so the BC treatment period was not included. Adherence was defined as a medication possession ratio of 380%. A CVD event was defined as an ischemic event or acute heart failure. Patients with a CVD event prior to diagnosis were excluded. Logistic regression was performed for each non-cancer condition to define factors associated with medication non-adherence. Cox regression was used to calculate the association between CVD medication adherence and time-to-subsequent cardiac events, adjusted for baseline factors. Cox regression was performed separately for each non-cancer condition.

Results: Among 23,080 women with BC in the cohort, 15,576 were adherent to at least one CVD medication prior to diagnosis, and of these, 2732 (17.5%) were non-adherent to at least one medication following treatment. Among the women adherent to medications prior to diagnosis, 19.2% were non-adherent to hypertension medications, 26.2% were non-adherent to cholesterol medications, and 30.6% were non-adherent to diabetes medications following the first year of BC treatment. Factors that were associated with non-adherence to anti-hypertensives included receipt of chemotherapy (OR 1.24, p&lt;0.001), other comorbidities (OR 1.34, p&lt;0.001), higher stage (OR 1.18, p &lt;0.001) and hormone receptor negative tumors (OR 1.15, p&lt;0.001). Similar factors were associated with non-adherence to cholesterol medications, whereas only stage and tumor type were associated with non-adherence to diabetes medications. Non-adherence to hypertension medications compared to adherence following diagnosis was associated with an increased risk of having a CVD event (HR 1.33, 95% CI 1.18-1.51, p&lt;0.001; 5-year cumulative incidence of 32% vs 26%, respectively, p&lt;0.001). Similar results were seen for adherence to cholesterol medications (HR 1.21, 95% CI 1.05-1.40, p=0.009) and diabetes medications (HR 1.31, 95% CI 1.09-1.56, p=0.003).

Conclusions:In summary, we found that a large proportion of women who were previously adherent to their medications to prevent CVD events prior to their breast cancer diagnosis were non-adherent following treatment. Of concern, non-adherence to any of these classes of medications resulted in an increased risk of having a cardiovascular event. Improving outcomes and reducing morbidity following a breast cancer diagnosis also requires focused attention on non-breast cancer conditions.

Citation Format: Hershman DL, Accordino M, Shen S, Buono D, Crew KD, Kalinsky K, Trivedi MS, Unger JM, Wright JD. Association between adherence to cardiovascular medications and cardiovascular events following a diagnosis of early stage breast cancer [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr PD6-10.