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

BACKGROUND: 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. METHODS: 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. RESULTS: 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. CONCLUSION: 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.

Geographical heterogeneity in the American Joint committee on Cancer oral cancer staging and prognostic implications.

OBJECTIVES: The AJCC 8th edition (AJCC 8) has introduced depth of invasion (DOI) and extranodal extension (ENE) into staging for oral squamous cell carcinoma (OSCC). Although validations have been performed on institutional datasets have shown a good performance, particularly in early OSCC, there have been no studies on diverse patient populations that determine the impact on prognostic heterogeneity. MATERIALS AND METHODS: 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) as endpoint, the prognostic performance of AJCC 7th and 8th editions were compared using Akaike Information Criterion (AIC), Bayesian Information Criteria (BIC), Harrell's concordance index (C-index). RESULTS: When comparing AJCC 8 to AJCC 7, the heterogeneity in prediction of OS increased for T-category and N-category while remaining unchanged for TNM staging, suggesting AJCC 8 increased complexity with no improvement in predictive value. There were significant differences in median DOI and incidence of ENE between geographical regions, resulting in dissimilar rates of stage-migration when adopting AJCC 8. CONCLUSION: In an attempt to improve prognostic performance, AJCC 8 introduced more variables; however heterogeneity in these results in significant geographical differences in model discrimination and performance. Caution should be applied as this may result in inaccurate and unreliable prognostic predictions that may impact treatment recommendations.