Perioperative phase angle decline is associated with postoperative sarcopenia in esophageal cancer: a longitudinal cohort study with internal validation

Background and aim Sarcopenia is highly prevalent in patients with esophageal squamous cell carcinoma (ESCC) and is associated with increased postoperative complications, prolonged hospitalization, and reduced survival. While preoperative PhA has been associated with clinical outcomes, the association between perioperative PhA change and postoperative sarcopenia remains unexplored. This study aimed to evaluate whether perioperative phase angle decline (ΔPhA) is associated with postoperative sarcopenia (Sarcopenia_Post). We also assessed the association between preoperative PhA (PhA_Pre) and postoperative outcomes. Methods In a prospective longitudinal cohort of 90 patients undergoing esophagectomy for ESCC, phase angle was measured 1 day before and 1 month after surgery. Associations of the primary outcome postoperative sarcopenia with ΔPhA (dichotomized at the cohort mean of 0.32°) were assessed using multivariate logistic regression, adjusting for preoperative sarcopenia and nutritional risk (NRS2002 ≥ 3). Model robustness was confirmed using internal validation approaches including ridge regression, bootstrap validation and random forest benchmarking. Multivariate analyses also assessed associations between PhA_Pre and postoperative outcomes. Results A pronounced perioperative decline in PhA (≥0.32°) was independently associated with postoperative sarcopenia after adjusting for preoperative sarcopenia and nutritional risk (adjusted Odds Ratio (aOR) = 4.69, 95% CI: 1.08–20.45, p = 0.040). This association was robust, as demonstrated by internal validation techniques. The model demonstrated good discriminatory power (AUC = 0.84, 95% CI: 0.72–0.96). In contrast, the static preoperative phase angle was not significantly associated with postoperative sarcopenia, overall complications, infectious complications, or length of stay in multivariate analyses. Conclusion Perioperative phase angle decline is associated with postoperative sarcopenia in patients with ESCC. Given the concurrent timing of assessments, this finding reflects association rather than prediction. The dynamic nature of phase angle change may provide valuable insights into postoperative sarcopenia, and further longitudinal studies with earlier PhA assessments are needed to determine whether perioperative PhA change has predictive utility for subsequent sarcopenia development.