Acceptance and Commitment Therapy to support medication decision-making and quality of life in women with breast cancer: protocol for a pilot randomised controlled trial

Background: Adherence to adjuvant endocrine therapy is affected by medication side-effects and associated distress. Previous interventions focused on educating women to enhance adherence have proved minimally effective. We co-designed an Acceptance and Commitment Therapy (ACT) intervention to enhance medication decision-making and quality of life by targeting a broader range of factors, including side-effect management and psychological flexibility. This study aims to establish key trial parameters, assess the acceptability of the intervention and the extent to which it can be delivered with fidelity, and to demonstrate "proof of principle" regarding its efficacy on primary and process outcomes. Methods: The ACTION intervention includes an individual 1:1 ACT session followed by three group sessions involving 8-10 women and two practitioner psychologists. Participants are also provided with access to a website containing evidence-based methods for self-managing side-effects. The ACT sessions were adapted during the COVID-19 pandemic to be remotely delivered via video conferencing software. To evaluate the feasibility and acceptability of this intervention, a multi-site, exploratory, two-arm, individually randomised external pilot trial with a nested qualitative study will be undertaken. Eighty women with early stage breast cancer prescribed adjuvant endocrine therapy will be randomised (1:1) to receive treatment as usual or treatment as usual plus the ACTION intervention. The planned future primary outcome is medication adherence assessed by the ASK-12 measure. Progression to a phase III RCT will be based on criteria related to recruitment and follow-up rates, acceptability to patients, competency and fidelity of delivery, and proof of principle for change in medication adherence. Discussion: This external pilot trial will be used to ascertain the feasibility of undertaking a future phase III RCT to definitively evaluate an ACT-based intervention to support medication taking behaviour and quality of life in women with early stage breast cancer on adjuvant endocrine therapy.