382. NUMBER OF LYMPH NODES RESECTED IS ASSOCIATED WITH OVERALL SURVIVAL IN PATHOLOGICALLY NODE-NEGATIVE ESOPHAGEAL CANCER

Abstract Background Lymphadenectomy is a key part of curative resection of esophageal cancer, with multiple quality assurance systems suggesting a minimum of 15 lymph nodes should be resected and subjected to pathological examination. Nevertheless, whether the absolute number of nodes resected is a surrogate marker for quality in surgery and staging, or has therapeutic benefit is debated. The aim of this study was to determine the impact of lymphadenectomy on survival in patients with resected pathologically node-negative disease (both treated and untreated with neoadjuvant therapy). Methods A review of our institutional prospectively maintained database was conducted from 2010-2020 inclusive. Inclusion criteria were patients undergoing esophagectomy for esophageal cancer aged 18+ who consented to data inclusion. Exclusion criteria were patients undergoing resection for benign disease, patients with Siewert III tumours undergoing gastrectomy or extended total gastrectomy, patients undergoing re-operative surgery, or patients where final pathology was not available. Univariable and multivariable analyses were performed as appropriate. Results 195 patients (49%) had pathologically node negative disease, with median lymph node count of 25. 47% of patients were clinically node positive, but pathologically node negative following neoadjuvant therapy. On univariable survival analysis, number of nodes resected was a significant predictor of overall survival (HR 0.96, 0.93-0.98, p=0.001). On multivariable analysis, R status (HR 4.9, 1.2-21.1, p=0.03), number of nodes resected (HR 0.97, 0.94-0.99, p=0.02) and prior cN+ status (HR 2.28, 1.16-4.49, p=0.02) were predictors of overall survival. Patients with cN0, (y)pN0 disease had improved overall survival compared with cN+, (y)pN0 (median not reached vs 43.4 months, p=0.04). Conclusion Lymphadenectomy is a key part of resection of esophageal cancer. In pathologically node negative patients, the extent of lymphadenectomy remains a key predictor of overall survival. Conversion from clinically node positive to pathologically node negative disease is associated with worse outcomes compared to clinically and pathologically node negative disease. Even in early stage cancer, a thorough, multi-field lymphadenectomy should be encouraged.