PROJECT SUMMARY/ABSTRACT Our team’s long-term goal is to promote the health and well-being of “metavivors,” a growing population of individuals living long-term with metastatic cancer as a chronic and terminal disease. New therapies have offered prolonged survival among metavivors but commonly produce side effects that can significantly impair quality of life. Many metavivors are women with metastatic breast cancer (MBC) treated with a CDK4/6 inhibitor. CDK4/6 inhibitors, like many other novel therapies for metavivors, are highly fatiguing. Cognitive behavioral therapy for fatigue (CBTF) is an evidence-based intervention that has produced large and durable improvements in fatigue among patients with curable cancers but has not been tested specifically for metavivors. In this clinical trial planning project, we will adapt CBTF for women with MBC treated with a CDK4/6 inhibitor and evaluate the feasibility, acceptability, and preliminary efficacy of the adapted intervention (“Energize-MBC”). The central hypothesis is that Energize-MBC will be feasible, acceptable, and will provide preliminary indications of reduced fatigue (primary outcome) and improved functioning (secondary outcome). Our specific aims are to: 1) adapt CBTF to the needs of women with MBC treated with a CDK4/6 inhibitor (i.e., Energize-MBC); 2) refine and finalize a web-based platform to deliver Energize-MBC via telemedicine; and 3) test the feasibility, acceptability, and preliminary efficacy of Energize-MBC via a pilot RCT. To achieve these aims, we will solicit patient (n=20) and provider (n=10) feedback via semi-structured interviews to adapt the CBTF intervention for women with MBC, conduct usability testing with MBC patients (n=10) to refine the Energize-MBC web-based platform, and then pilot test the 16-week telemedicine Energize-MBC intervention with MBC patients (n=60). Participants in the pilot RCT will complete baseline questionnaires at enrollment and will be randomized 2:1 to the Energize- MBC intervention or usual care (waitlist) control. Participants will wear ActiGraph GT9X activity trackers at baseline and follow-up to assess objective sleep and physical activity. The Energize-MBC intervention content will be tailored for individual participants based on responses to their baseline questionnaires, with selected intervention modules completed by patients online via the Energize-MBC web-based platform. Interventionists will maintain accountability by checking in weekly via text or email, as well as a maximum of two telephone or video consultations. All participants will be asked to complete self-report questionnaires immediately post- intervention or at a corresponding time for controls (i.e., 16 weeks post-baseline). A priori benchmarks will be used to define intervention feasibility and acceptability. These data will be used as the basis for a future, full- scale, multisite Phase II trial of Energize-MBC. This rigorous and impactful line of research aligns with NCI’s priority focus on well-planned clinical trials aimed at improving management of treatment-related symptoms, supportive care, and the long-term outcomes of cancer survivors.

PROJECT NARRATIVE Women with metastatic breast cancer (MBC) treated with a CDK4/6 inhibitor exemplify a new and growing population of patients living long-term with metastatic cancer as a chronic and fatal condition (i.e., “metavivors”). In the current study, we will adapt an existing cognitive behavioral therapy intervention for fatigue (CBTF) for fatigued metavivors with MBC treated with a CDK4/6 inhibitor. We will then evaluate the feasibility, acceptability, and preliminary efficacy of the adapted intervention, called Energize-MBC, in preparation for a full-scale, multisite Phase II trial with high potential impact.