Validation of the TNM-8 AJCC classification for HPV-positive oropharyngeal cancers in patients undergoing trans-oral robotic surgery.

High-risk human papillomaviruses (HPV) are associated with some oropharyngeal squamous cell carcinomas (OPSCC). HPV-OPSCC have better survival outcomes compared to HPV negative tumours. The new TNM-8 AJCC staging (2018) is based on ICON-S data with 98% of patients treated with primary chemoradiation. To validate the TNM-8 AJCC classification in HPV-OPSCC treated primarily with surgery (trans-oral robotic surgery or open). There were 102 patients with HPV-OPSCC treated between July 2009 and December 2014 at the Royal Adelaide Hospital. The median age was 57 years (range: 38-83) and mostly males (84.5%). 27.2% were active smokers and 50.5% reformed smokers. Early T-stage cancer in 72.8%. Primary treatment was surgery & adjuvant therapy (70%) while primary chemoradiation (30%). Survival analyses were performed for the 7th and 8th AJCC systems. The reclassification to the AJCC 8th edition staging system resulted in a change of 54 patients from stage 4 to stages 1 and 2. This was mainly an effect of changes with N2a and N2b nodal disease being reclassified to N1. Survival outcomes were comparable with the ICON-S data. The new TNM-8 classification is, therefore, validated in a cohort treated, predominantly, with primary surgery and adjuvant therapy.