Wigle, D.

334 Background: Sarcopenia, or decreased skeletal muscle mass, has been associated with worse surgical and oncologic outcomes across multiple malignancies. This study investigates the impact of sarcopenia on outcomes after multimodal therapy for esophageal cancer. Methods: Retrospective observational cohort study including adult patients who underwent neoadjuvant therapy followed by esophagectomy for primary esophageal cancer from January 2000 - December 2021. A fully automated abdominal segmentation using deep convolutional neural network was utilized to calculate skeletal muscle index (SMI) from preoperative CT scans performed at our institution. Males with SMI <52.4 cm 2 /m 2 and females with SMI <38.5 cm 2 /m 2 at any point before surgery were classified as sarcopenic. The relationship between sarcopenia and patient demographics, operative details, and complications were explored using chi-square tests. The relationship between sarcopenia and disease-free survival and overall survival were investigated using parsimonious multivariable analysis retaining variables with p-value <0.05 using backward selection method. Results: We identified 200 patients meeting the study criteria with 142 (71%) having sarcopenia at any time prior to surgery. Patients with sarcopenia were significantly older [65.2 (59.6, 71.2) vs 63 (53.6, 67.5), p = .023] and more likely to have had open surgery [129 (90.8%) vs 46 (79.3%), p = .034]. There were no significant differences in sex, history of diabetes, coronary artery disease, renal disease, smoking, cancer type, cancer stage, tumor size, tumor location, or margin status between sarcopenic groups ( p > .05). Sarcopenic patients were significantly more likely to require blood transfusion ≥3 units after esophagectomy [79 (55.6%) vs 8 (13.8%), p < .001] or to experience complications requiring surgical intervention [36 (24.6%) vs 7 (12.1%), p = .048]. Multivariate analysis revealed that sarcopenia was associated with disease-free and overall survival (Table). Conclusions: Sarcopenia is a prognostic factor in patients undergoing multimodal therapy for esophageal cancer. Interventions that aim to prevent decreases in SMI after initiating neoadjuvant therapy should be investigated. Multivariate analysis with sarcopenia predicting outcomes. Disease free survivalHR (95% CI) p-value Overall survivalHR (95% CI) p-value Age 1.04 (1.02, 1.06) < .001 1.04 (1.02, 1.07) < .001 Epicenter Middle Upper 1.88 (1.21, 2.86)3.16 (1.67, 5.98) .001.005< .001 1.96 (1.26, 3.04)4.00 (1.90, 8.44) < .001.003< .001 Stage Stage II Stage III Stage IV 1.88 (0.95, 3.71)2.90 (1.46, 5.75)16.02 (6.12, 41.93) < .001.069.002< .001 1.65 (0.83, 3.25)2.76 (1.37, 5.55)10.14 (4.03, 25.53) < .001.151.005< .001 Cancer type - - 1.76 (1.03, 3.02) .039 Transfusion > 3 pRBC - - 1.54 (0.99, 2.40) .057 BMI prior to cancer diagnosis - - 0.98 (0.94, 1.01 .208 Sarcopenic 1.76 (1.16, 2.67) .007 1.64 (1.04, 2.60) .033