Associations of body composition with neoadjuvant chemotherapy response, toxicity, and prognosis in breast cancer: a scoping review.

BACKGROUND: Breast cancer is the leading cause of cancer-related death in women worldwide. There is increasing interest in using detailed body composition parameters, such as skeletal muscle mass and adiposity, to better predict treatment response, toxicity, and survival in breast cancer patients receiving neoadjuvant chemotherapy (NAC). This study synthesised current literature on the effect of body composition in breast cancer patients undergoing NAC and identified gaps for future research. METHODS: A scoping review was conducted in accordance with PRISMA-ScR and Arksey & O'Malley frameworks. Embase, MEDLINE, PubMed, and Google Scholar were searched for studies published between 2010 and 2025 to map available evidence. Eligible studies included female breast cancer patients receiving NAC with body composition assessment and at least one outcome of response, toxicity, or prognosis. RESULTS: Twenty studies met inclusion criteria. Computed tomography at the L3 vertebral level was the most common assessment method. Findings were heterogeneous; 3 studies reported a statistically significant association between sarcopenia and reduced pathological response, while results for adiposity were inconsistent. Half of the studies assessing toxicity reported higher toxicity rates in patients with sarcopenia and/or adiposity. Prognostic findings were variable, with some studies reporting associations with visceral adiposity, and only one study reporting a significant association with sarcopenia. CONCLUSIONS: Evidence regarding the relationship between adiposity and NAC toxicity and prognosis in breast cancer remains suggestive, while findings for sarcopenia are inconsistent. Prospective, standardised studies are needed to clarify the role of body composition in breast cancer outcomes and its relevance in treatment planning.