How applicable is the TNM 8 staging for human papillomavirus (HPV) related oropharyngeal squamous cell carcinoma (OPSCC) to a UK population of 106 patients? : A cohort comparison of the TNM 7 and TNM8 staging systems for HPV positive oropharyngeal cancer in a UK population.

Purpose: TNM8 introduced a new staging system for HPV positive oropharyngeal squamous cell carcinoma (OPSCC). This study aimed to investigate whether the changes made in TNM8 offer the perceived benefit in prognostication when compared to TNM7 in a specific patient population in the North East of England.

Methods: A retrospective cohort comparison study of all patients with HPV positive OPSCC (n = 106) through the Newcastle Head and Neck MDT between January 2012 to December 2014. Overall survival (OS) and Disease specific survival (DSS) data at 3 years was gathered for both TNM7 and TNM8. Log rank test was used to compare survival curves. Harrell's C-index adjusted for age and smoking status was used to assess prognostic ability of the two staging methods.

Results: TNM8 downstages disease (TNM7 stage IV patients n = 74, TNM8 stage IV patients n = 2) but gives a more even distribution of patients across disease stages. Survival for TNM8 stage II and III is similar. In our small cohort, the log-rank test detected differences in OS between stages for both scoring methods (TNM7 p = 0.006, TNM8 p < 0.001) and similarly for DSS (TNM7 p = 0.001, TNM8 p < 0.001). Harrell's C-index was similar for both models for OS (TNM7 0.71, TNM8 0.71) and DSS (TNM7 0.74, TNM8 0.70).

Conclusion: TNM8 downstages disease and prognosticates well for stage I disease but does not differentiate between stage II and III disease when compared to TNM7. Further adaptation is required to address this to make TNM8 a more accurate prognostic tool.