The <scp>RESILIENT</scp> Study: A Retrospective, Descriptive, Correlational Investigation of Correlates of Oral Endocrine Therapy Adherence in Older Women With Breast Cancer

BACKGROUND: Breast cancer is the most prevalent and costly cancer. Oral endocrine therapy (OET) improves survival rates and quality of life while reducing recurrence, mortality, morbidity, and medical costs. However, adherence to OET is challenging because OET is prescribed for 5-10 years. Determinants of OET nonadherence (NA) among women aged 65 and older remain poorly characterized. Existing studies are limited, often focusing on small, single-site samples and focusing on patient-level rather than multi-level determinants. Despite the unique needs of older women, research on OET-NA remains scarce. OBJECTIVE: This study identified multi-level determinants of OET-NA in older women using ecological systems theory and the World Health Organization's five-dimension model. METHODS: A descriptive, correlational secondary data analysis was conducted using the 2019 Surveillance-Epidemiology-End-Results (SEER) Medicare database, which includes more than 9 million cancer cases in the United States. RESULT: OET-NA was significantly affected by (a) patient-related factors of ethnicity (i.e., Black [AOR 1.55; 95% CI 1.34-1.78; p < 0.001]) and psychological issues (i.e., depression [OR 1.40; 95% CI 1.27-1.54; p < 0.001]), (b) socioeconomic-related factors of marital status (i.e., divorced [OR 1.17; 95% CI 1.04-1.32; p ≤ 0.01]), and lifestyle (i.e., tobacco use [OR 1.41; 95% CI 1.22-1.63; p < 0.001]), (c) therapy-related factors of switching OET medications (OR 2.72; 95% CI 2.41-3.07; p < 0.001), (d) condition-related factors of comorbidities (i.e., obesity [OR 1.13; 95% CI 1.03-1.23; p < 0.01]), and (e) characteristics of the healthcare team and health system-related factors (i.e., group practice type [OR 1.26; 95% CI 1.01-1.56; p < 0.05]). CONCLUSION: OET-NA was associated with multi-level determinants, including being Black, having depression, being divorced, using tobacco, switching OET medications, having obesity, and receiving care in group practices. Identifying these determinants is a critical first step toward developing and testing interventions to improve OET-NA and enhance survival and quality of life.