Psoas muscle depletion correlates with poor prognosis and compromised immunity in resectable gastric cancer: A multicenter study.

Sarcopenia, assessed by the psoas muscle index (PMI), is characterized with the loss of skeletal muscle mass and strength, and has gained growing attentions in the field of cancers. However, its role in gastric cancer (GC), especially in patients received gastrectomy, remains underexplored. This multicenter retrospective study examined 439 patients with resectable GC to assess the prognostic significance of sarcopenia, measured by PMI and PMI change rate (PMICR), while also exploring potential links with tumor immunity. Kaplan-Meier analysis revealed that low PMICR was significantly associated with worse survival outcomes in all patient cohorts. Further multivariate Cox analysis identified PMICR (hazard ratio: 2.80, 95% CI: 1.73-4.56), but not baseline PMI-as an independent predictor of overall survival. Immunologically, low PMICR patients exhibited decreased tertiary lymphoid structure density and reduced tumor-infiltrating lymphocytes (CD3+ T cells and CD20+ B cells). The developed nomogram incorporating PMICR showed superior prognostic performance versus TNM stage, with concordance indices of 0.821 (95% CI: 0.789-0.853), 0.800 (95% CI: 0.753-0.847), and 0.816 (95% CI: 0.743-0.889) for training, internal validation, and external validation cohorts, respectively. These results suggested that PMICR, as a measure of sarcopenia, more accurately predicted survival outcomes and might be associated with immune status in resectable GC patients. Moreover, the newly developed nomogram demonstrated high accuracy in predicting prognosis.