Protocol of a randomized trial of acceptance and commitment therapy for fatigue interference in metastatic breast cancer.

Fatigue interference with activities, mood, and cognition is one of the most prevalent and distressing concerns of metastatic breast cancer patients. To date, there are no evidence-based interventions for reducing fatigue interference in metastatic breast cancer and other advanced cancer populations. In pilot studies, Acceptance and Commitment Therapy (ACT) has shown potential for reducing symptom-related suffering in cancer patients. The current Phase II trial seeks to more definitively examine the efficacy of telephone-based ACT for women with metastatic breast cancer who are experiencing fatigue interference. In this trial, 250 women are randomly assigned to either the ACT intervention or an education/support control condition. Women in both conditions attend six weekly 50-min telephone sessions. The primary aim of this study is to test the effect of telephone-based ACT on fatigue interference. Secondary outcomes include sleep interference, engagement in daily activities, and quality of life. Outcomes are assessed at baseline, 2 weeks post-intervention, and 3 and 6 months post-intervention. This trial also examines whether increases in psychological flexibility, defined as full awareness of the present moment while persisting in behaviors aligned with personal values, account for the beneficial effect of ACT on fatigue interference. After demonstrating ACT's efficacy, the intervention can be widely disseminated to clinicians who care for metastatic breast cancer patients. Our findings will also inform future ACT trials with various cancer populations and functional outcomes.