Sarcopenia in Breast Cancer Patients: A Systematic Review and Meta-Analysis

Simple Summary: The evaluation of additional body composition measures, such as visceral adipose tissue area, subcutaneous adipose tissue area, and sarcopenic obesity, could be useful to improve our understanding of the prognostic role of body composition parameters in women with breast cancer. The aim of our review was to summarize current evidence about sarcopenia in non-metastatic as well as metastatic breast cancer (MBC) and to identify any correlation between sarcopenia and patient outcomes. We observed a correlation between sarcopenia and significantly higher rates of treatment-related toxicities in both settings (metastatic and non-metastatic) compared with patients without sarcopenia. It was found that sarcopenic patients were more likely to deal with severe toxicities compared to patients classified as non-sarcopenic. This finding suggests that sarcopenia recently emerged as a new condition that, independently from malnutrition, may adversely affect patient outcomes and may be used as a reference for chemotherapy dose selection to better balance individual pharmacokinetic differences. (1) Background: We estimated the prevalence and clinical outcomes of sarcopenia among breast cancer patients. (2) Methods: A systematic literature search was carried out for the period between July 2023 and October 2023. Studies with breast cancer patients evaluated for sarcopenia in relation to overall survival (OS), progression-free survival (PFS), relapse of disease (DFS), pathological complete response (pCR), or toxicity to chemotherapy were included. (3) Results: Out of 359 screened studies, 16 were eligible for meta-analysis, including 6130 patients, of whom 5284 with non-MBC. Sarcopenia was evaluated with the computed tomography (CT) scan skeletal muscle index and, in two studies, with the dual-energy x-ray absorptiometry (DEXA) appendicular lean mass index. Using different classifications and cut-off points, overall, there were 2007 sarcopenic patients (33%), of whom 1901 (95%) presented with non-MBC. Sarcopenia was associated with a 33% and 29% higher risk of mortality and progression/relapse of disease, respectively. Sarcopenic patients were more likely to develop grade 3-4 toxicity (OR 3.58, 95% CI 2.11-6.06, p < 0.0001). In the neoadjuvant setting, a higher rate of pCR was observed among sarcopenic patients (49%) (OR 2.74, 95% CI 0.92-8.22). (4) Conclusions: Our meta-analysis confirms the correlation between sarcopenia and negative outcomes, especially in terms of higher toxicity.