Abstract
BACKGROUND: Many patients with metastatic breast cancer can live relatively long lives but are challenged by treatment- and cancer-related side effects such as weight gain, physical deconditioning, and reduced quality of life, possibly affecting survival. In particular, endocrine treatments are associated with an increased risk of weight gain and adverse metabolic effects. There is a need for interventions to prevent side effects among patients with disseminated breast cancer. Exercise is found to be effective in improving quality of life, metabolic health, and body composition in the curative setting, yet evidence in the metastatic setting is sparse. The aim of this study is to assess feasibility of a 12-week exercise intervention for metastatic breast cancer patients with overweight receiving endocrine therapy and to explore potential effects on metabolic health, body composition, physical performance, obesity-related biomarkers, and patient-reported outcomes. METHODS: The FEMA study is a randomized controlled feasibility trial in which 21 endocrine-treated patients with metastatic breast cancer and overweight will be randomly assigned in a 2:1 ratio to either a 12-week training program with three weekly training sessions (intervention), or usual care (control), which includes standard clinical follow-up and supportive care without structured exercise. Feasibility will be assessed based on recruitment rate, adherence, retention, and acceptability, employing both quantitative and qualitative approaches for data collection. Participants' experiences will be explored by interviews and analyzed based on content analysis. Data are collected from blood samples, bioelectrical impedance analysis, physical performance tests, blood pressure measurements, and validated questionnaires on health-related quality of life, self-efficacy for coping with cancer, and sleep quality for explorative analyses. DISCUSSION: The planned study will allow us to determine whether this 12-week exercise intervention is feasible in endocrine-treated metastatic breast cancer patients with overweight and explore potential effects on metabolic health, body composition, physical performance, obesity-related biomarkers, and patient-reported outcomes. Information from feasibility outcomes will inform the design of a future definitive randomized controlled trial. TRIAL REGISTRATION: Retrospectively registered on March 6, 2024, at ClinicalTrials.gov (NCT06343987).