Developing a complex intervention to support medication adherence in cancer

Adjuvant endocrine therapy (AET) reduces the risk of breast cancer recurrence and mortality, but up to three-quarters of women do not take AET as prescribed. Most existing interventions aiming to support AET adherence have not been effective. Guided by the Multiphase Optimisation Strategy (MOST), this PhD aimed to develop and assess the acceptability of a complex intervention to support AET adherence.

Study One combined Intervention Mapping with MOST to identify barriers to adherence, and develop a conceptual model. The intervention components included; 1) text messages targeting habit formation; 2) an information leaflet targeting medication beliefs; 3) a guided self-help acceptance and commitment therapy programme targeting psychological distress (via increasing psychological flexibility); and 4) self-management website targeting side-effects. Study Two involved a series of studies using mixed-methods to develop text messages promoting habit formation to support AET adherence. A pool of 66 messages, considered acceptable to women with breast cancer and showing fidelity to intended behaviour change techniques, were developed. Study Three used a 2^5 factorial experiment to optimise the content of the information leaflet to increase necessity beliefs and reduce concerns. The leaflet comprised five components. Quotes and pictures from breast cancer survivors was the only component to have a main effect on medication beliefs. There were also four significant interaction effects between other components. A stepped decision-making process led the enhanced side-effect information to be screened out of the optimised leaflet. Study four was a mixed-methods process evaluation, nested in a pilot trial, which aimed to investigate the acceptability of the four intervention components, guided by the theoretical framework of acceptability. All four components were considered acceptable to women taking AET.

A complex intervention aiming to support AET adherence was developed and considered acceptable to women with breast cancer. This intervention will now be optimised in an optimisation trial.