Adherence to endocrine therapy and its determinants in patients with hormone receptor positive breast cancer at Moi Teaching and Referral Hospital

Abstract

Background: Endocrine therapy is the cornerstone of management for early-stage hormone receptor positive breast cancer with significant clinically relevant outcomes like improved disease-free and overall survival, better response rates, reduction in recurrence and distant metastases and improvement in quality of life. Adherence to endocrine therapy is the key determinant in achieving these improved outcomes. This adherence has however been reported to be sub-optimal in clinical practice globally with limited data from Africa and Moi Teaching and Referral Hospital (MTRH). Objectives: To determine the proportion of Hormone Receptor Positive (HR+) breast cancer patients in MTRH with good adherence to endocrine therapy and to identify the determinants of adherence. Methods: A cross-sectional, descriptive, sequential explanatory mixed-methods study was conducted at the outpatient oncology clinic of MTRH from February 2024 to February 2025. Eligible participants were adults aged 18 years or older, with documented hormone receptor positivity, Stage I–III breast cancer, on endocrine therapy for at least two months. Participants were enrolled through consecutive sampling until the target sample size of 131 was achieved. Data collection involved patient interviews, chart reviews, and prescription assessments. Quantitative adherence was assessed using the Voils DOSE non-adherence scale, with good adherence defined by a mean score of ≤1. For qualitative analysis, 11 patients participated in-depth interviews to explore determinants of adherence, and thematic analysis was employed to identify patterns and themes related to adherence to endocrine therapy. Results: The majority of participants were female (97%), aged 40–59 years (61%), had attained secondary-level education (50.4%), and a substantial proportion (70.2%) reported having no formal employment or regular income. Overall, 72.5% of participants reported good adherence to endocrine therapy. Patients aged 50–59 years exhibited a significantly higher proportion of good adherence (p = 0.002), and higher educational attainment was strongly associated with good adherence. Advanced disease stage (Stage III) and use of anastrozole (p = 0.016) were also significantly associated with good adherence. In multivariate analysis, patients aged 50–59 years (adjusted odds ratio [aOR] = 4.21, p = 0.040) and those with tertiary-level education (aOR = 3.23, p = 0.043) were significantly more likely to demonstrate good adherence to endocrine therapy. Although travel time and transport costs were not statistically significant predictors of adherence in the quantitative analysis, qualitative findings identified these factors as substantial barriers, with participants describing the burden of long travel distances and expressing the need for more accessible treatment facilities. Conclusion: A significant proportion of the HR+ patients living with breast cancer reported good adherence to endocrine therapy. Higher education level, older age, advanced disease stage and anastrozole use were associated with good adherence. Recommendations: Develop targeted interventions for younger and less-educated patients to overcome barriers and improve endocrine therapy adherence.