Abstract PO2-11-01: Prevalence of Nonadherence to Endocrine Therapy and Cardiovascular Medications Among Breast Cancer Survivors

Abstract Background: Cardiovascular disease (CVD) and cancer are the two leading causes of death in the U.S, and breast cancer (BC) is the most common cancer among women. Most survivors of early-stage BC are prescribed adjuvant endocrine therapy (ET) to decrease their BC recurrence risk; many of them are also on statins and/or antihypertensives to manage concurrent CVD risk factors. Nonadherence to ET or CVD medications is associated with decreased survival and other poor outcomes, yet little is known about how best to identify nonadherence to multiple classes of medications in BC survivors. Methods: We reviewed pharmacy fill data from our electronic health record (EHR) for a diverse cohort of patients seen in our breast oncology clinic with prescriptions for ET and CVD medications (statin and/or antihypertensive(s)). Patients were excluded if their pharmacy data did not show both an active ET order and an active CVD order or fill. Nonadherence to any medication was defined as proportion of days covered (PDC) 80% over the previous 180 days. A subset of patients also responded to a patient-reported nonadherence screener administered through our EHR at appointment registration starting in 2/2022. Descriptive statistics were used to determine the prevalence of nonadherence to all medications (defined as PDC 80% for either ET and/or CVD medications) and for each class of medication separately. We also compared the PDC-based combined nonadherence to the self-reported nonadherence. Results: We identified a total of 1,015 BC survivors on ET and CVD medications last seen in clinic between 2/1/2020 and 6/6/2023 (mean age 69 yo; 23.6% non-Hispanic White, 11.3% non-Hispanic Black, and 38.9% Hispanic). Of these, 567 (55.9%) were prescribed ET and statins, and 745 (73.4%) were prescribed ET and antihypertensives. With nonadherence defined as PDC 80% for any medication (ET and/or CVD medications), the nonadherence prevalence was 38.4%. The nonadherence prevalence by medication class was slightly lower for ET (20.7%) than for statins (25.9%) and antihypertensives (25.0%). Among patients on ET and statins, 10.1% were nonadherent to both medications and 24.3% were nonadherent to only 1 class of medications; the proportion of patients nonadherent to ET only was almost half that of patients nonadherent to statins only (8.5% vs 15.9%). A similar trend was observed among patients on ET and antihypertensives: 10.3% were nonadherent to both classes of medications and 26.2% were nonadherent to only 1 class of medications, with 11.5% of patients nonadherent to ET only and 14.6% nonadherent to antihypertensives only. Of the 1,015 patients, 390 (38.4%) responded to the nonadherence screener between 2/16/2022 and 6/6/2023, of which 93 (23.8%) reported any level of medication nonadherence. Among these, 57 (61.3%) had PDC≥ 80% and thus were categorized as adherent under our PDC-based adherence determination. Of the 297 patients who self-reported adherence to all medications on the screener, 32.3% had PDC 80% for any medication. When combining nonadherence by PDC and self-report, the overall nonadherence rate for the 390 patients who responded to the screener was considerably higher at 48.5% (vs 33.8% by PDC only and 23.8% by self-report only). Conclusions: EHR-based screening can identify patients with or at risk for medication nonadherence for targeted interventions. Using a combined approach of pharmacy fill data and patient reports, close to 50% of patients were identified as having nonadherence to at least 1 medication. Nonadherence to statins and antihypertensives was more common than nonadherence to ET, which is concerning as early-stage BC survivors are more likely to die from CVD than BC. Interventions to improve adherence to multiple classes of medications are warranted in this population. Citation Format: Claire Sathe, David DeStephano, Shing Lee, Melissa Beauchemin, Nadia Liyanage-Don, Melissa Accordino, Katherine Crew, Ian Kronish, Dawn Hershman. Prevalence of Nonadherence to Endocrine Therapy and Cardiovascular Medications Among Breast Cancer Survivors abstract. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO2-11-01.