Bioelectrical impedance analysis-derived water composition ratios predict survival outcomes in gastric cancer: a...

Bioelectrical impedance analysis (BIA)-derived water composition ratios are non-invasive and cost-effective indices that reflect body fluid distribution. This study aimed to investigate the associations between these BIA-derived ratios and overall survival (OS) in patients with gastric cancer. A retrospective multicentre study included 385 gastric cancer patients. Optimal cut-offs were determined via receiver operating characteristic curves. Kaplan-Meier survival analysis, Cox regression analysis and restricted cubic spline (RCS) evaluated associations with OS. The optimal cut-off values were 0.389 for extracellular water (ECW)/total body water (TBW), 0·611 for intracellular water (ICW]/TBW and 0·638 for ECW/ICW. Kaplan-Meier survival analysis revealed that elevated ECW/TBW (72·6% vs. 58·7%; P < 0·001) and ECW/ICW (59·1% vs. 72·4%; P < 0·001) were associated with poorer OS, while a higher ICW/TBW (73·4% vs. 57·3%; P < 0·001) indicated better prognosis. In RCS models, ECW/TBW (hazard ratio (HR) = 1·552, 1·202-2·005, P = 0·001) and ECW/ICW (HR = 1·735, 1·320-2·280, P < 0·001) independently predicted worse OS, whereas ICW/TBW inversely correlated with mortality (HR = 0·620, 0·486-0·790, P < 0·001). Multivariable Cox regression analysis further confirmed that higher ECW/TBW (HR =1·552, 95% CI 1·272-2·688, P < 0·001) and ECW/ICW (HR = 1·735, 1·320-2·280, P < 0·001) ratios independently predicted worse OS. Conversely, a higher ICW/TBW ratio was inversely correlated with mortality (HR = 0·567, 95% CI 0·390-0·824, P = 0·003). The ECW/ICW ratio demonstrated the highest C-index (0·596), outperforming other ratios in predicting survival. These associations were consistent across subgroups, including advanced-stage patients. BIA-derived water composition ratios, particularly ECW/ICW, are robust and independent predictors of survival in gastric cancer patients, reflecting underlying metabolic and inflammatory disturbances. These non-invasive and cost-effective markers could enhance prognostic accuracy and guide personalised treatment strategies.