Skeletal muscle loss during neoadjuvant chemotherapy as a predictor of major postoperative complications in esophageal cancer patients.

310 Background: Preoperative malnutrition and sarcopenia are known risk factors for postoperative complications. Nutritional therapy and rehabilitation during the perioperative period may help prevent these conditions and contribute to improved postoperative outcomes. Even among patients without pre-treatment sarcopenia, some may experience muscle loss during neoadjuvant chemotherapy (NAC). In this study, we investigated the association between changes in skeletal muscle mass during NAC and postoperative outcomes in non-sarcopenic patients using the Psoas Muscle Index (PMI) as a surrogate marker of nutritional status. Methods: Among 399 patients who underwent esophagectomy for thoracic esophageal squamous cell carcinoma at our institution between 2015 and 2023, 151 received NAC. Of these, 62 patients with pre-NAC sarcopenia were excluded, and the remaining 89 non-sarcopenic patients were retrospectively analyzed. Skeletal muscle mass was assessed by PMI measured at the L3 level on CT. The PMI ratio was defined as the post-NAC PMI expressed as a percentage of the pre-NAC value. Based on time-dependent ROC analysis using overall survival (OS), a cut-off of 90% in PMI ratio was determined, dividing patients into a PMI-decreased group (