Extracellular water to total body water ratio predicts survival in cancer patients with sarcopenia: a multi-center cohort study

BACKGROUND: Body water measured by bioelectrical impedance analysis (BIA) predicts the outcomes of many diseases. This study aimed to evaluate the relationship between body water and the prognosis of cancer patients with sarcopenia. METHODS: This study employed 287 cancer patients with sarcopenia underwent BIA from a prospective multicenter study of patients with cancer in China from 2013 to 2020. The primary outcome of interest was all-cause mortality presented as the longest time to follow-up available. Eight indicators of body water [total body water, extracellular water, intracellular water, free fat mass, active cell mass, extracellular water/intracellular water, extracellular water/total body water (ECW/TBW), and intracellular water/total body water] were included in the research. Neutrophil–lymphocyte ratio (NLR) = neutrophil (× 10(9))/lymphocyte (× 10(9)). The discriminatory ability and prediction accuracy of each factor were assessed using the C-index. The hazard ratios (HR) and 95% confidence intervals (CI) were calculated using the Cox proportional hazard model. RESULTS: The median age was 65 years old, and 138 (48%) patients were men. During a mean follow-up of 46 months, 140 deaths were recorded, resulting in a rate of 204.6 events per 1000 patient-years. ECW/TBW showed the best predictive accuracy (C-index = 0.619) compared to the other indicators [p = 0.004, adjusted HR (95% CI) 1.70 (1.18,2.44)]. In the middle tertile (0.385–0.405), ECW/TBW had a strong independent negative association with patient survival [adjusted HR (95% CI) 2.88 (1.39–5.97), p = 0.004]. Patients who had a high ECW/TBW (ECW/TBW ≥ 0.395) combined with a high NLR had 3.84-fold risk of mortality (p < 0.001, 95% CI 1.99,7.38). CONCLUSIONS: ECW/TBW was better than other indicators in predicting survival of cancer patients with sarcopenia. High ECW/TBW combined with high NLR would further increase the risk of mortality. Trial registration: The Investigation on Nutrition Status and Clinical Outcome of Common Cancers (INSCOC) (Chinese Clinical Trial Registry: ChiCTR1800020329, URL of registration: http://www.chictr.org.cn/showprojen.aspx?proj=31813). SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12986-022-00667-3.