Comparison of the seventh and eighth editions of the American Joint Committee on Cancer (AJCC) staging for oropharyngeal squamous cell carcinomas (OPSCC): A Surveillance, Epidemiology and End Results Program (SEER) database analysis.

Abstract

e17538 Background: The recently released eighth edition of the American Joint Committee on Cancer (AJCC) Staging Manual, Head and Neck Section, incorporates significant changes to the prior seventh edition. The changes reflect the improved understanding of tumor biology, prognostic factors and molecular markers that effect outcomes in Head and Neck cancers. A key update restages OPSCC by human papilloma virus (HPV) positive and negative cancers as data demonstrated that these tumors have significantly different biology and outcomes. Methods: Using SEER data from 2004 – 2014, we identified male patients with squamous cell carcinomas of the tonsil, base of tongue and soft palate aged between 21 and 64 years old (those clinical characterizes were considered as surrogate markers for HPV positive status). We classified them by the AJCC 8th edition staging for HPV positive OPSCC and by AJCC 7th edition staging. The prediction performance by two staging editions were compared regarding overall survival (OS) and Disease free survival (DFS). Kaplan-Meier method and Cox proportional hazard model were applied, and the discrimination performance was measured by the concordance statistics (C-statistics). Results: A total of 8202 eligible patients were included in the analysis with a median follow up period of 51 months. 7415 (90.4%) patients had previously received radiation and 7038 (85.8%) patients had previously received chemotherapy. The median age of patients was 56 years. Distribution of stage I disease increased from 2% to 19.6% in AJCC 8th edition. 10-year overall survival (OS) for AJCC 8th stages I (74%), II (78%), III (55%) and IV (32%). Using Stage I as reference, the hazard ratio for stage II, III, and IV is 0.98 (95%CI: 0.87-1.09), 2.29 (95%CI: 2.04-2.57), and 5.88 (95%CI: 4.96-6.98). Similar results were noted for ten year disease free survival. The C-statistics measured overall discrimination for 8th edition is 0.68 and 0.63 for the 7th edition (P < 0.001). Conclusions: Based on this SEER analysis, the overall performance of discrimination improved from AJCC 7th to 8th edition; but in this study population, AJCC 8th edition does not distinguish stage I and II sufficiently as expected as it does for stages III and IV disease. Limitations of the SEER database include the surrogate for P16 status and under reported and incomplete data.