Sarcopenia in patients with metastatic breast cancer: A systematic review and meta-analysis

Sarcopenia is associated with poor treatment outcomes and survival in early breast cancer and other cancer types. This systematic review and meta-analysis evaluated sarcopenia's prevalence and clinical implications for metastatic breast cancer-an area that remains underexplored.

A systematic literature review searched CINAHL, Cochrane Library, Embase, and Ovid MEDLINE for studies published before October 2024. A meta-analysis using a random- or fixed-effects model calculated mean differences in skeletal muscle index (SMI) and assessed the association with progression-free and overall survival. The study protocol was registered on PROSPERO (CRD42024557390).

Fourteen studies involving 1472 participants with metastatic breast cancer were included. The pooled overall sarcopenia prevalence was 41.6 % (95 % CI 35.4 %-48.7 %), with variability driven by differing SMI cutoffs (38-41 cm²/m²). The pooled mean SMI was 41.01 cm²/m² (95 % CI 38.81-43.21, p < .001), with significant heterogeneity (I² = 95.3 %). Subgroup analysis revealed that patients treated with cyclin-dependent kinase 4 and 6 (CDK4/6) inhibitors as first-line treatment had an SMI of 42.08 cm²/m². Our synthesized review showed heterogeneous association between sarcopenia and poor treatment outcomes. Sarcopenia's impact on progression-free survival (hazard ratio = 1.17, 95 % CI 0.43-1.91) and overall survival (hazard ratio = 0.99, 95 % CI 0.96-1.01) was not statistically significant.

Sarcopenia is prevalent and clinically meaningful in metastatic breast cancer. While its direct role in survival remains inconclusive, early assessment of sarcopenia by molecular subtype and treatment timing is crucial for optimizing care.