Reduced impact of nodal metastases as a prognostic factor for tonsil cancer in the HPV era.

Metastatic lymph nodes (LN) are an adverse prognostic factor in head and neck squamous cell carcinoma (SCC). In this study, we tested the hypothesis that nodal metastases have reduced impact on survival in tonsil cancer in the HPV-predominant era. Incidence and mortality data of tonsil and oral cavity SCC between 1988 and 2007 were obtained from the SEER database. Based on published literature, we considered cases of tonsil cancer from 1988 to 1997 as the pre-HPV cohort (N = 752), and 1998-2007 as the HPV-predominant cohort (N = 2,755). Comparing the two cohorts, Kaplan-Meier 5-year overall survival (OS) for tonsil SCC improved from 54.0 to 74.3 % (p < 0.0001), and cancer-specific survival (CSS) improved from 66.0 to 82.9 % (p < 0.0001). Stratifying by LN involvement showed improved OS in the HPV-predominant cohort with one (63.6 vs. 79.7 %, p < 0.0001), two to three (54.2 vs. 75.9 %, p < 0.0001), four to eight (40.3 vs. 68.9 %, p < 0.0001), and greater than eight positive nodes (25.5 vs. 41.9 %, p < 0.0001). While metastatic LNs still negatively affect prognosis, their impact on OPC survival has diminished in the HPV-predominant era. This finding provides a rationale for additional studies of the prognostic significance of LN metastases in OPC cohorts of defined HPV status, and supports the concept that HPV-related OPC is a disease distinct from "classical" OPC, with unique prognostic features.