Study design and protocol for tailored Acceptance and Commitment Therapy (ACT) to optimize quality of life in women living with metastatic breast cancer.

Women living with metastatic (stage IV) breast cancer face unique challenges, including arduous treatments, side effects, chronic symptom burden, and emotional distress. Nevertheless, most research has paradoxically focused on optimizing quality of life in women with early-stage, non-metastatic breast cancer. Acceptance and Commitment Therapy (ACT) is an evidence-based, third-wave cognitive behavioral therapy that focuses on creating 'a life worth living' by promoting meaning and purpose and optimizing quality of life. ACT may be particularly well-suited for women with metastatic breast cancer as it addresses salient existential concerns, while allowing for the co-occurrence of feelings of grief and loss that are normal and expected when facing a life-limiting prognosis. This manuscript describes the rationale and study design of a pilot randomized controlled trial to develop and assess the feasibility and acceptability of a tailored ACT intervention for women living with metastatic breast cancer. Participants (N = 30) will be randomized 1:1 to either ACT, cognitive behavioral stress management (CBSM), or a usual care control. Both ACT and CBSM are 8-week, group-based interventions that will be delivered online. Primary outcomes are rates of acceptance, retention, and satisfaction. Preliminary effects on variables of interest, including meaning and purpose, psychological flexibility, and several domains of quality of life, will also be examined. Findings will inform the conduct of a full-scale randomized controlled trial of our tailored ACT intervention in women living with metastatic breast cancer.