Confirmation of the 8th edition of the AJCC/UICC TNM staging system for HPV-mediated oropharyngeal cancer in Japan

Background: Several studies have demonstrated that the 7th edition of the AJCC/UICC TNM staging classification system does not consistently distinguish between prognostic subgroups for human papillomavirus (HPV)-mediated oropharyngeal squamous cell carcinoma (OPSCC). The 8th edition of the AJCC/UICC TNM staging came into effect for use with HPV-mediated OPSCC on or after January 1, 2017. This study confirms that the 8th edition of the AJCC/UICC TNM staging system for HPV- mediated OPSCC accurately reflects disease outcomes. Patients and methods:We retrospectively analyzed 195 patients with OPSCC treated at Hokkaido University Hospital, Sapporo, Japan between 1998 and 2015. HPV status was evaluated by immunohistochemical analysis of p16. Results: Of the 195 OPSCC patients, 111 (56.9%) were p16 positive, and 84 (43.1%) were p16 negative. The 3-year overall survival rate (OS) was significantly lower in the p16-negative patients with stage III-IV in comparison with those with stage I-II (55.0% vs 93.1%, p<0.01). The 3-year OS did not differ significantly between stage I-II and stage III-IV in the p16-positive patients (86.7% vs 87.7%). According to the 8th edition of the AJCC/UICC TNM staging system, stage I-II and stage III could be differentiated on the basis of the 3-year OS in the p16-positive patients (90.9% vs 70.2%, p