Preoperative Muscle Quality and Postoperative Computed Tomography-Defined Muscle Loss Predict Prognosis After Gastrectomy for Gastric Cancer.

BACKGROUND & AIMS: Body weight (BW) loss after gastrectomy is commonly monitored, but it may not accurately reflect skeletal muscle depletion. We investigated the prognostic significance of postoperative CT-defined muscle loss after curative gastrectomy, with RFS as the primary endpoint. METHODS: We retrospectively analyzed 341 patients with pStage I-III gastric cancer who underwent curative gastrectomy and had evaluable CT at approximately 6 months after surgery. Preoperative intramuscular adipose tissue content (IMAC) and postoperative psoas muscle index (PMI) loss were evaluated in relation to recurrence-free survival (RFS) and overall survival (OS). RESULTS: The correlation between 6-month BW loss and PMI loss was weak (R2=0.063, p<0.001), with discordant phenotypes in 39.8% of patients. On multivariable analysis, in addition to pT4 and pN positivity, both high preoperative IMAC and high PMI loss rate remained independently associated with worse RFS (Hazard Ratio (HR) 1.90 and 6.41, respectively) and OS (HR 1.68 and 2.95, respectively), whereas preoperative PMI and BW loss rate were not significant. Combined stratification further identified patients with both high preoperative IMAC and high postoperative PMI loss as having the poorest prognosis; their 5-year RFS and OS rates were 51.0% and 41.9%, respectively, compared with 93.2% and 84.3% in the Low/Low group. CONCLUSIONS: BW loss is an imprecise surrogate for postoperative muscle depletion. Preoperative muscle quality and postoperative muscle loss provide complementary prognostic information after gastrectomy.