Human papillomavirus modifies the prognostic significance of T stage and possibly N stage in tonsillar cancer

Despite the association with more advanced nodal stage, patients with human papillomavirus (HPV) positive oropharyngeal cancers have better outcomes. We examined whether the HPV can modify the effect of known prognostic factors in tonsillar cancer. A total of 489 patients from 10 centres were followed up for recurrence or death for a median of 3.2 years. Determinants of the rate of locoregional recurrence, death from tonsillar cancer and overall survival were modelled using Cox regression. The prognostic value of T and N stages were modified by HPV as indicated by statistically significant interaction terms. After adjusting for age, gender and treatment, T stage appeared relevant only for HPV-positive cancers (where a higher T stage was associated with worse outcomes). There was some evidence that N stage was a more relevant prognostic factor for HPV-negative than -positive cancers. There was no evidence that the HPV modifies the effect of age, gender or grade on outcomes. This study suggests that the prognostic significance of the conventional staging system in tonsillar cancer is modified by HPV.