Survival of patients with oropharyngeal squamous cell carcinomas (OPSCC) in relation to TNM 8 - Risk of incorrect downstaging of HPV-mediated non-tonsillar, non-base of tongue carcinomas

Abstract

Background: TNM-8 staging separates oropharyngeal squamous cell carcinomas (OPSCC) into human papillomavirus (HPV)-mediated and -unrelated OPSCC based on p16INK4a overexpression (p16+), as surrogate marker for HPV. However, OPSCC is histologically and clinically heterogenous including tonsillar and base of tongue squamous cell carcinomas (TSCC and BOTSCC respectively), and carcinomas of soft palate and walls (otherOPSCC). The significance of HPV is established in TSCC/BOTSCC, while its role in otherOPSCC is unclear, which is not considered in TNM-8. Here, p16+ was therefore evaluated in relation to overall survival (OS) and tumor stage per OPSCC subsite.

Patients and methods: All 932 patients, treated with curative intent in Stockholm 2000-2016 with OPSCC, previously analyzed for p16 expression, were included. Clinical data, including stage and OS, was collected retrospectively.

Results: Patients with p16+ otherOPSCC had significantly poorer OS compared to patients with p16+ TSCC/BOTSCC (p = 0.005) and their survival was similar to that of patients with p16-otherOPSCC/TSCC/BOTSCC. Moreover, patients with TNM-8 stage I-II and p16+ otherOPSCC had a significant poorer OS compared to patients with p16+ TSCC/BOTSCC and similar stage (p = 0.02). Lastly, patients with otherOPSCC and low TNM-7 stage had a significant better OS, as compared to those with a high stage (p = 0.019) while no hazard discrimination was observed with TNM-7 in TSCC/BOTSCC.

Conclusion: Our results indicate a risk of misclassification of patients with otherOPSCC and low TNM-8 stage. We suggest that p16 should only be evaluated in TSCC/BOTSCC and that patients with otherOPSCC should all be staged as patients with HPV-unrelated (p16-) OPSCC.

Keywords: HPV; Oropharyngeal carcinoma; Survival; TNM-8; p16.