OBJECTIVES: Approximately 70-80% of breast cancer expresses hormone receptors (HR) (estrogen and progesterone receptors) and are called HR+ breast cancer. OET, including Tamoxifen and aromatase inhibitors are considered standard adjuvant therapy for HR+ breast cancer. OET, by blocking estrogen production and actions, reduces breast cancer recurrence, metastasis, and mortality. The minimum duration of OET in breast cancer patients is 5 years, with even longer treatment duration shown to improve outcomes. Despite demonstrated benefits, nearly 50% of patients are non-adherent and 70% discontinue therapy before the recommended 5 years. Our objective was to identify and summarize literature-reported barriers associated with non-adherence/ non-persistence to OET among breast cancer survivors.

METHODS: A PUBMED literature search was conducted in June, 2017 using the following terms: ‘breast cancer’, ‘oral endocrine therapy’ or ‘oral hormone therapy’ or ‘Tamoxifen’ or ‘Aromatase Inhibitors’, ‘adherence’ or ‘barriers’. The search was restricted to past five years. The abstracts of each result were reviewed and categorized as either patient-reported or physician-reported. All patient- and physician-reported factors that affected adherence and persistence were listed and grouped together into the three main categories: Socio-demographic and medical parameters, general psychosocial parameters, and psychosocial parameters related to OET.

RESULTS: A total of 315 articles were identified, of which 20 met inclusion criteria. Adverse drug reactions were the most commonly reported barrier but were generally under-reported among physicians. Among patient-reported barriers, common social-demographic and medical parameters were age, comorbidity, and financial status. General psychosocial variables were lack of patient-provider communication, depressive symptoms, and lack of perceived self-efficacy. Treatment toxicity was the most commonly reported psychosocial parameter related to OET.

CONCLUSIONS: The determinants of non-adherence and non-persistence are multi-dimensional and influenced by several factors. The three categories of adherence barriers should be evaluated and considered when designing future interventions to enhance OET adherence for a tailored approach.