17Background: Neutrophil-to-lymphocyte ratio (NLR) has been identified as a biomarker for a number of malignancies, with higher ratios being associated with poorer oncologic outcomes. Rather than purely an indicator of advanced disease there is emerging evidence that neutrophils are directly implicated in facilitating cancer progression, and thus alterations and trends of neutrophil counts and NLR during different phases of treatment may reflect a change in oncologic outcome that is as important, or more so, as the absolute count or NLR at baseline. The aim of this study is to investigate the prognostic role of neutrophil-to-lymphocyte ratio trends during the treatment trajectory of patients with esophageal adenocarcinoma. Methods: This is a retrospective study of patients who underwent esophagectomy for esophageal adenocarcinoma between 2005-2016. NLR was measured at three time points: baseline, during neoadjuvant chemotherapy (NAC), and in the late postoperative period. Primary outcomes were overall (OS...