807. A REVISED APPROACH TO THE ESOPHAGOGASTRIC JUNCTION: A MODIFIED SIEWERT CLASSIFICATION

Abstract Background Esophagogastric junction (EGJ) adenocarcinomas are challenging due to their anatomical and histopathological features and treated either as part of the esophagus or stomach cancers. Siewert (S) and Nishi classifications rely on the tumor’s epicenter to guide treatment decisions, which can lead to diagnostic and therapeutic inconsistencies. Moreover, recent studies helped define the optimal extent of lymphadenectomy for EGJ cancers. Here we present our standardized approach to EGJ cancers that integrates these insights, providing a framework to guide clinical decision-making. Methods Our modified classification relies on tumor extent rather than the epicentre, based on endoscopic measurement of the proximal and the distal limits, and the exact location of the EGJ. This approach classifies tumors based on their extent which results into six categories: SI, SI/II, SII, SII/III, SIII, and SI/II/III. Lower esophageal tumors whose distal limit lies between + 1cm and -2cm are classified as I/II. Cardia tumors whose proximal limit falls between those boundaries are II/III. Tumors that span more cephalad than + 1cm and more distally than – 2cm, are I/II/III. For Siewert I, I/II and II tumors, surgical management depends on the extent of esophageal involvement, mainly dictated by the probability of mediastinal basement nodal involvement, as defined by Kurokawa et al (2019). Additionally, a 3-field lymphadenectomy is performed when there is involvement of the cervical or recurrent laryngeal nerve lymph node stations. Results In SI, SI/II, and SI/II/III, with esophageal involvement exceeding 4 cm we favor a transthoracic esophagectomy (TTE) with total thoracic lymphadenectomy. If the involvement is between 1-4 cm, a transhiatal esophagectomy (THE) with lower mediastinal lymphadenectomy is performed. In SII, THE is done for 0-1 cm of involvement; absence of esophageal involvement permits a transhiatal extended total gastrectomy (eTG) with abdominal D2 lymphadenectomy and intra-operative margin status assessment via frozen sections. In SI/II/III and esophageal involvement of more than 4 cm, TTE is required; for esophageal involvement of 1-4 cm, we perform a THE and total gastrectomy with abdominal D2 lymphadenectomy based on distal margin findings. Conclusion This proposed modification to the classification of EGJ adenocarcinomas introduces a comprehensive framework that is tailored to the extent of tumor involvement. By addressing the limitations of existing systems and incorporating current insights, this updated classification aims to improve patient categorization and standardize treatment protocols, potentially leading to enhanced clinical outcomes.