Sarcopenia in Breast Cancer Patients: Prevalence, Clinical Impact, and Practical Approaches to Assessment

Sarcopenia has emerged as a prevalent and clinically significant condition among breast cancer patients, characterized by loss of skeletal muscle mass accompanied by declines in muscle strength and physical performance. Increasing evidence indicates that sarcopenia occurs across all stages of breast cancer and throughout the treatment continuum, including at diagnosis, during active therapy, and into survivorship. Tumour-related metabolic alterations, systemic inflammation, anticancer treatments, physical inactivity, and inadequate nutritional intake collectively contribute to muscle depletion in this population. In breast cancer patients, sarcopenia has been consistently associated with poorer treatment tolerance, increased cancer-related fatigue, functional decline, and adverse clinical outcomes, even in individuals with preserved body weight or coexisting obesity. The reported prevalence of sarcopenia varies widely depending on patient characteristics, treatment phase, and assessment methodology, with pooled estimates approaching nearly half of affected patients in some cohorts. While imaging-based techniques such as computed tomography and positron emission tomography–computed tomography provide precise quantification of muscle mass and quality, their routine clinical use is limited by cost, accessibility, and resource constraints. Consequently, practical bedside tools including bioelectrical impedance analysis, anthropometric measurements, and functional performance tests have gained increasing attention as feasible options for screening and longitudinal monitoring. This narrative review synthesizes current evidence on the prevalence, pathophysiology, clinical and functional consequences, and assessment approaches for sarcopenia in breast cancer patients. Emphasis is placed on the dynamic nature of sarcopenia across the disease trajectory and the importance of early recognition, comprehensive assessment, and integration of muscle health evaluation into standard breast cancer care. Adoption of practical assessment strategies may facilitate timely interventions, optimize functional outcomes, and improve quality of life during and after cancer treatment.