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.