Clinical impact of CT-defined sarcopenia on long-term oncological outcomes in gastric cancer: validation of muscle mass cut-offs established according to EWGSOP recommendations.

BACKGROUND: Sarcopenia is an important prognostic factor in gastrointestinal malignancies, but CT-based definitions vary. This study evaluated recently published computed tomography (CT)-based cut-offs for skeletal muscle index (SMI) and psoas muscle thickness normalized to height (PMTH), derived from a young, presumably healthy reference population according to recommendations of the European Working Group on Sarcopenia in Older People (EWGSOP), in patients undergoing surgery for gastric cancer. METHODS: This retrospective, single-center cohort study included patients who underwent surgery for gastric cancer between 2013 and 2018. Preoperative CT was used to assess SMI and PMTH. The recently published reference cut-offs were compared with the established definitions of Prado et al. (SMI) and Gu et al. (PMTH). Overall survival (OS) and recurrence-free survival (RFS) were the primary and secondary endpoints, respectively. RESULTS: Data from 212 patients with complete 5-year follow-up were analyzed. The reference cut-offs significantly discriminated OS and RFS (SMI, both p < 0.001; PMTH, both p = 0.002), whereas the established cut-offs showed weaker or no discrimination. Patients with both low SMI and low PMTH had the worst OS and RFS (both p < 0.001). Combined low SMI and low PMTH was associated with worse OS in univariable analysis (HR 2.57, 95% CI 1.54-4.30, p < 0.001) and remained independently associated in multivariable analysis (HR 1.83, 95% CI 1.01-3.30; p = 0.046). CONCLUSIONS: The recently published CT-based reference cut-offs for SMI and PMTH provided consistent prognostic stratification after gastric cancer resection, and their combined use identified patients with particularly poor long-term survival.