Background: The recently published American Joint Committee on Cancer (AJCC) 8th edition introduces a new staging system for human papilloma virus positive (HPV+) oropharyngeal cancer (OPC) with separate clinical and pathological staging criteria. Patients treated with (chemo)radiation will not be staged pathologically, as opposed to surgical patients, who will be staged with both criteria. Comparability in staging between patients treated with different modalities will be important moving forward. To date, no studies have used preoperative imaging and postoperative pathology to compare the new clinical and pathologic staging systems.
Objective: To compare the AJCC 8th edition HPV+ OPC clinical and pathological staging systems for intersystem agreement
Methods: Data was collected retrospectively on surgically-managed HPV+ OPC patients at a single tertiary care academic center between January 1, 2009 and June 31, 2017. Preoperative imaging and pathology reports were used to stage patients based on the AJCC 8th edition clinical and pathological staging systems, respectively.
Results: A total of 213 patients met inclusion criteria. Both the clinical and pathological AJCC 8th edition TNM staging system met significance in predicting disease-free survival (p=0.008 and p=0.0004, respectively). In comparing the AJCC 8th edition clinical and pathologic staging systems to each other, chi-square testing demonstrated significant association (p<0.0001) but Kappa statistics showed poor agreement (κ=0.3275). In our population, 30.3% of patient’s preoperative 8th edition clinical stage changed based on the postoperative pathologic staging with 73.4% of those being upstaged.
Conclusion: Both the new clinical and pathological HPV+ OPC staging systems accurately predict survival and clinical outcomes. However, disagreement between systems exists with some disagreement occurring due to the separate clinical and pathological staging criteria even when the preoperative radiographic findings match surgical specimen findings. The significance of this discrepancy should be considered as the new system is implemented in clinical medicine and research moving forward.