Muscle mass, assessed at diagnosis by L3-CT scan as a prognostic marker of clinical outcomes in patients with gastric cancer: A systematic review and meta-analysis.

BACKGROUND & AIMS: Computed tomographic (CT) imaging at third lumbar vertebra (L3), routinely used by oncologists, represents a reliable tool to quantify muscle mass. A systematic review and meta-analysis was performed to assess the efficacy of CT scan to define muscle mass as a prognostic marker in gastric cancer (GC) patients undergoing gastrectomy and/or chemotherapy. The primary outcomes were overall survival (OS) and recurrence-free survival (RFS) and the secondary outcomes included postoperative length of hospital stay (P-LOS), total and severe complications in GC patients undergoing gastrectomy. METHODS: Three electronic bibliographic databases - MEDLINE, Web of Science and Cochrane Central Register of Controlled Trials - were used to conduct a systematic literature search based on fixed inclusion and exclusion criteria, until April 2019. The adjusted and unadjusted hazard ratio (HR), odds ratio (OR) and mean difference (MD) with 95% confidence interval (CI) were used to analyse the dichotomous variables (OS, RFS, total and severe complications) and continuous variables (P-LOS). Random- and fixed effects models were used according to the heterogeneity. RESULTS: A total of 5610 GC patients from 20 studies were identified. Low muscle mass at diagnosis was found in 32.7% of GC patients and was significantly associated with poorer OS (HR 2.02, 95% CI 1.71-2.38, p < 0.00001, I2 = 47%) and worse RFS (HR 1.97, 95% CI 1.71-2.26, p < 0.00001, I2 = 0%). Meta-analysis of adjusted HR from multivariable analyses confirmed the association between OS and low muscle mass (HR 1.89, 95% CI 1.68-2.12, p < 0.00001, I2 = 36%). Furthermore, low muscle mass and poorer OS were significantly associated in metastatic GC patients exclusively undergoing chemotherapy (HR 1.61, 95% CI 1.23-2.11, p < 0.0006, I2 = 18%). Moreover, preoperative low muscle mass was significantly associated with longer P-LOS (MD 1.19, 95% CI 0.68-1.71, p < 0.00001, I2 = 0%), higher risk of postoperative complications (OR 1.76, 95% CI 1.17-2.66, p = 0.007, I2 = 77%) and severe complications (OR 1.54, 95% CI 1.03-2.29, p = 0.04, I2 = 49%) in GC patients undergoing gastrectomy. CONCLUSIONS: Low muscle mass, assessed by L3 CT-scan, affects almost 1/3 of GC patients at diagnosis and acts as a negative prognostic marker on many clinical outcomes. Therefore, identifying GC patients with low muscle mass at diagnosis or at follow-up visit should be recommendable. Clinical nutritionists should be part of tumor boards meetings to screen low muscle mass in order to prompt personalized nutritional support.