Extracellular-to-Intracellular Fluid Volume Ratio as a Prognostic Factor for Survival in Patients With Metastatic Cancer

Purpose: This study aimed to investigate whether the extracellular-to-intracellular fluid volume (E/I) ratio can predict survival in patients with metastatic cancer. Methods: Clinical data were collected from April 2016 to March 2018. Patients aged ≥19 years with metastatic solid tumor were eligible. Bioimpedance analysis was used to assess body fluid distribution and the E/I ratio. Clinical characteristics, including laboratory test results and nutrition status according to the E/I ratio, were analyzed. Cox proportional hazards models and Kaplan-Meier analysis were used to identify risk factors for mortality. Results: In total, 87 patients were included in the study. The 87 patients were divided into 2 groups according to the median E/I ratio: a high E/I group (E/I ratio ≥1.0, n = 43) and a low E/I group (E/I ratio <1.0, n = 44). Poor performance status, fluid retention, malnutrition, elevation of C-reactive protein levels, and decreases in hemoglobin, albumin, and protein levels were significantly associated with the high E/I group. The median overall survival time was 1.6 and 12.5 months in the high E/I and low E/I groups, respectively (P < .001). In the multivariate analysis, poor performance status, leukocytosis, fluid retention, and E/I ratio were independent prognostic factors, and the E/I ratio was the strongest prognostic factor predicting overall survival (hazard ratio = 3.49, 95% confidence interval = 1.75-6.96, P < .001). Conclusions: The E/I ratio can predict survival time in patients with metastatic cancer. More rigorous research is required to confirm this result.