Improving accuracy in nodal staging of oral cancer: Proposal of a new system

Despite introduction of extranodal extension (ENE) into the AJCC 8th edition of oral cancer staging, previous criticisms persist, such as limited discrimination between sub-stages and doubtful prognostic value of contralateral nodal disease. The purpose of this study was to compare our novel nodal staging system, based on the number of positive nodes and ENE, to the AJCC staging system in surgically treated patients. Retrospective analysis of 4710 patients with oral squamous cell carcinoma (OSCC) treated with surgery±adjuvant therapy in 8 institutions in Australia, North America and Asia. With overall survival (OS) and disease specific survival (DSS) as endpoint, the prognostic performance of AJCC 8th and 7th editions were compared using hazard consistency, hazard discrimination, likelihood difference and balance. Our new nodal staging system (PN) a progressive and linear increase in hazard ratio (HR) from pN0 to pN3, with good separation of Kaplan Meier curves. Using the predetermined criteria for evaluation of a staging system, our proposed staging model outperformed AJCC 8th and 7th editions in prediction of OS and DSS. PN was the lymph node staging system that provided the most accurate prediction of OS and DSS for patients in our cohort of OSCC. Additionally, it can be easily adopted, addresses the shortcomings of the existing systems and should be considered for future editions of the TNM staging system. •Despite improvements, oral cancer nodal staging has remained complex and inaccurate.•Our work supports number of positive nodes, not size, to improve performance.•When combined with extranodal extension, this new system improved accuracy.•This approach needs to be considered in newer iterations of the staging system. Lay summary: Despite improvements, oral cancer nodal staging has remained complex and inaccurate. Our novel staging system supports adopting number of positive nodes, and not node size, to improve staging performance. When combined with extranodal extension, this new system objectively improved accuracy in nodal staging. This approach needs to be considered in newer iterations of the staging system.Synopsis: Although the AJCC/UICC 8th edition improved nodal staging, there is still complexity and inefficiencies that need to be addressed. In this study we looked at alternate staging systems and compared them based on several objective criteria. Number of positive nodes, when combined with the presence of extranodal extension, was the most