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

Abstract

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. 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. 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 (β\u2009=\u20090.145, 95% CI: 0.011 to 0.279, p\u2009=\u20090.034) and negatively associated with barriers (β\u2009=\u2009− 0.381, 95% CI: − 0.511 to − 0.251, p\u2009<\u20090.001). There was no effect of Necessity (β\u2009=\u20090.006, 95% CI: − 0.145 to 0.158, p\u2009=\u20090.933) or Concerns (β\u2009=\u20090.041, 95% CI: − 0.117 to 0.199, p\u2009=\u20090.614) on adherence. Necessity-concerns beliefs were also not significant mediators in the relationship between socio-clinico factors and medication adherence. 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.