Identification of patients at risk for poor survival among those with normal skeletal muscle mass: a multicenter retrospective validation study in gastric cancer

BACKGROUND: Although a low skeletal muscle mass index (SMI) leads to poor overall survival (OS) after gastrectomy in patients with gastric cancer, the cutoff value that predicts long-term survival in patients with normal SMI remains unclear. This study aimed to determine the cutoff SMI value for predicting OS in patients with normal SMI. METHODS: This multicenter retrospective cohort study included patients with normal SMI who underwent radical gastrectomy for pStage I-III primary gastric cancer between January 2011 and December 2016. The patients were randomly divided at a 6:4 ratio into a training set, which examined the cutoff values for SMI, and a validation set, which validated the cutoff values. Patients were classified into high and low SMI groups according to the cutoff values. We compared OS between the high- and low-SMI groups using log-rank test and identified prognostic factors using Cox proportional hazards regression analysis. RESULTS: for women. Both men and women in the low-SMI group had poorer OS than those in the high-SMI group. Multivariate analysis revealed that a low SMI was an independent adverse prognostic factor for OS (hazard ratio: 1.314, 95% confidence interval: 1.044-1.654, P = 0.020). These cutoff values were associated with lower cancer-specific survival. CONCLUSIONS: Among patients with normal SMI, those with a lower SMI had poorer long-term survival after radical gastrectomy.