Informing interventions to improve uptake of adjuvant endocrine therapy in women with breast cancer: a theoretical-based examination of modifiable influences on non-adherence

Purpose To inform intervention development, we measured the modifiable determinants of endocrine therapy (ET) non-adherence in women with breast cancer, using the Theoretical Domains Framework (TDF) and examined inter-relationships between these determinants and non-adherence using the Perceptions and Practicalities Approach (PAPA). Methods Women with stages I-III breast cancer prescribed ET were identified from the National Cancer Registry Ireland (N = 2423) and invited to complete a questionnaire. A theoretically based model of non-adherence was developed using PAPA to examine inter-relationships between the 14 TDF domains of behaviour change and self-reported non-adherence. Structural equation modelling (SEM) was used to test the model. Results A total of 1606 women participated (response rate = 66%) of whom 395 (25%) were non-adherent. The final SEM with three mediating latent variables (LVs) (PAPA Perceptions: TDF domains, Beliefs about Capabilities,Beliefs about Consequences; PAPA Practicalities: TDF domain, Memory, Attention,Decision Processes and Environment) and four independent LVs (PAPA Perceptions: Illness intrusiveness; PAPA Practicalities: TDF domains, Knowledge,Behaviour Regulation; PAPA External Factors: TDF domain, Social Identity) explained 59% of the variance in non-adherence and had an acceptable fit (chi(2)(334) = 1002, p < 0.001; RMSEA = 0.03; CFI = 0.96 and SRMR = 0.07) Knowledge had a significant mediating effect on non-adherence through Beliefs about Consequences and Beliefs about Capabilities. Illness intrusiveness had a significant mediating effect on non-adherence through Beliefs about Consequences. Beliefsabout Consequences had a significant mediating effect on non-adherence through Memory, Attention, Decision Processesg and Environment. Conclusions By underpinning future interventions, this model has the potential to improve ET adherence and, hence, reduce recurrence and improve survival in breast cancer.

Automated summary

To develop intervention for endocrine therapy (ET) non-adherence in women with breast cancer, this study measured modifiable determinants using Theoretical Domains Framework (TDF) and examined their relationships using Perceptions and Practicalities Approach (PAPA). The final model explained 59% of non-adherence variance and had an acceptable fit. Knowledge mediated non-adherence through beliefs about consequences and capabilities. Illness intrusiveness mediated non-adherence through beliefs about consequences. Beliefs about consequences mediated non-adherence through memory, attention, decision processes, and environment.