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

Background Several studies have demonstrated that the seventh edition of the American Joint Committee on Cancer/American Joint Committee on Cancer (AJCC/UICC) TNM staging system does not consistently distinguish between prognostic subgroups for human papillomavirus (HPV)-mediated oropharyngeal squamous cell carcinoma (OPSCC). The eighth edition of the AJCC/UICC TNM staging system came into effect for use with HPV-mediated OPSCC on or after 1 January 2017. This study confirms that the eighth 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 evaluated, 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%, respectively; 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 eighth edition of the AJCC/UICC TNM staging system, stage I-II and stage III can be differentiated on the basis of the 3-year OS in the p16-positive patients (90.9 vs 70.2%, respectively; p < 0.01). Conclusions The seventh edition of the AJCC/UICC TNM staging system is suitable for use with p16-negative patients; however, it does not effectively discriminate between p16-positive patients. Therefore, the eighth edition of the AJCC/UICC TNM staging system is more suitable for HPV-mediated OPSCC in Japan.