Integrated Assessment of Skeletal Muscle Quantity and Quality Is Associated with Survival in Patients with Oesophagogastric Malignancies: A Retrospective Cohort Study

Background: Oesophagogastric cancer is associated with poor survival and major alterations in body composition. This study investigated the relationship between myopenia and myosteatosis in patients with oesophagogastric cancer and evaluated their prognostic significance and association with systemic inflammation. Methods: In this retrospective single-centre study, 161 consecutive patients diagnosed with oesophagogastric cancer between 2019 and 2023 underwent computed tomography-based body-composition analysis at diagnosis. Skeletal muscle index (SMI) and skeletal muscle density (SMD) were measured at the third lumbar vertebra. Myopenia and myosteatosis were defined using Martin’s criteria. Associations with overall survival (OS) and progression-free survival (PFS), and systemic inflammation assessed using C-reactive protein (CRP), neutrophil-to-lymphocyte ratio (NLR), and platelet-to-lymphocyte ratio (PLR), were analysed using Kaplan–Meier and Cox regression analyses. Results: Among the 161 patients included (67.1% male; median age 66 years), myopenia and myosteatosis were highly prevalent (62.7% and 87.6%, respectively), despite a median body mass index (BMI) within the normal range. Lowest SMI tertile was significantly associated with poorer OS and PFS, whereas lowest SMD tertile showed markedly reduced OS. On multivariate analyses, lower SMD remained independently associated with OS and with PFS, whereas SMI lost significance after adjustment for clinical and inflammatory factors. The coexistence of myopenia and myosteatosis was associated with significantly worse survival outcomes. An exploratory continuous muscle score integrating muscle quantity and muscle quality was associated with OS (hazard ratio 1.28 per SD increase) and demonstrated moderate prognostic discrimination (concordance-index 0.63). Conclusions: Muscle quantity and quality represent complementary dimensions of cancer-associated muscle impairment in oesophagogastric cancer. Collectively, these results suggest that a continuous measure integrating both muscle quantity and muscle quality provides a more clinically informative assessment of muscle impairment than traditional binary definitions of myopenia and myosteatosis.