Facilitators and barriers to medication adherence with adjuvant endocrine therapy in women with breast cancer: a structural equation modelling approach.

ABSTRACT

PURPOSE: To identify a structure to explain the relationship between socio-clinico factors, necessity-concerns beliefs, and perceived barriers to adherence with adjuvant endocrine therapy (AET) amongst women with breast cancer. METHODS: Participants were 244 patients with early-stage breast cancer recruited from two tertiary hospitals from May 2015 to December 2018 who completed questionnaires on medication adherence (Simplified Medication Adherence Questionnaire), necessity-concerns beliefs (Beliefs about Medicine Questionnaire), and barriers to adherence (Adherence Starts with Knowledge Questionnaire). Socio-clinico variables were collected via interview and medical records review. Structural equation modelling was applied to examine the relationships between these variables and possible mediating effects of necessity-concerns beliefs on adherence to AET. RESULTS: The median age of the study participants was 61 (range 32-80) years and the median duration on AET was 1.6 (IQR 1.2-2.6) years. Adherence was positively associated with age (ß = 0.145, 95% CI 0.011 to 0.279, p = 0.034) and negatively associated with barriers (ß = - 0.381, 95% CI - 0.511 to - 0.251, p < 0.001). There was no effect of Necessity (ß = 0.006, 95% CI - 0.145 to 0.158, p = 0.933) or Concerns (ß = 0.041, 95% CI - 0.117 to 0.199, p = 0.614) on adherence. Necessity-concerns beliefs were also not significant mediators in the relationship between socio-clinico factors and medication adherence. CONCLUSIONS: Older age and lower barriers to adherence were associated with higher adherence scores. Necessity-concerns beliefs did not have a significant effect on adherence as majority of the patients identified forgetfulness as a reason for non-adherence.