Staging HPV-related oropharyngeal cancer: Validation of AJCC-8 in a surgical cohort.

IMPORTANCE: The American Joint Committee on Cancer, 8th edition (AJCC-8) contains a new staging system for human papillomavirus (HPV)-related oropharyngeal squamous cell carcinoma (OPSCC). Our study aim was to evaluate the effectiveness of the AJCC-8 relative to the AJCC 7th edition (AJCC-7). MATERIALS AND METHODS: A retrospective chart review was performed on a multi-institutional, prospectively collected dataset from two tertiary referral centers. All patients had HPV+ OPSCC treated primarily with surgery. The prognostic value of AJCC-7 and AJCC-8 were compared for 5-year overall survival (OS) and disease-specific survival (DFS). RESULTS: AJCC-8 pathological staging effectively risk stratified patients, creating a Cox model with a better fit (lower Akaike's Information Criterion, p < 0.0001) when compared to AJCC-7 pathological stages for both OS and DFS. The AJCC-8 pathologic staging did not produce a better fit than the AJCC-8 clinical staging (p = 0.15) for OS, however, AJCC-8 pathologic was more effective than AJCC-8 clinical for DFS (p < 0.0001). 76% of patients did not change their stage between clinical and pathologic AJCC-8 staging; 14% were upstaged by 1, <1% were upstaged by 2, 7% were downstaged by 1, and 3% downstaged by 2. CONCLUSIONS AND RELEVANCE: The new AJCC-8 staging system represents a significant improvement over AJCC-7 for risk stratification into groups that predict overall survival and disease-specific survival of surgically treated HPV+ OPSCC patients. The AJCC- 8 pathologic staging system was not significantly better than the AJCC-8 clinical staging system for overall survival, however, the pathologic staging system was better than the clinical for disease free survival.