Radiotherapy alone as a possible de-intensified treatment for human papillomavirus-related locally advanced oropharyngeal squamous cell carcinoma.

Background: Human papillomavirus (HPV)-related oropharyngeal squamous cell carcinoma (OPSCC) is defined by p16 positivity and/or HPV DNA positivity. Because survival of patients with HPV-related OPSCC after chemoradiotherapy is favorable, a de-intensified treatment is expected to lead to less morbidity while maintaining low mortality. The association of tumor p16 and HPV DNA status with survival after radiotherapy alone remains unknown.
Methods: We retrospectively examined survival of 107 patients with locally advanced OPSCC after radiotherapy alone (n = 43) or chemoradiotherapy (n = 64) with respect to tumor p16 and HPV DNA status, using Cox's proportional hazard model.
Results: Survival after radiotherapy alone was significantly worse in p16-positive/HPV DNA-negative locally advanced OPSCC than in p16-positive/HPV DNA-positive locally advanced OPSCC. In bivariable analyses that included T category, N category, TNM stage, and smoking history, the survival disadvantage of p16-positive/HPV DNA-negative locally advanced OPSCC remained significant. There was no significant difference in survival after chemoradiotherapy between p16-positive/HPV DNA-positive locally advanced OPSCC and p16-positive/HPV DNA-negative locally advanced OPSCC. Survival in p16-positive/HPV DNA-positive locally advanced OPSCC after radiotherapy alone was similar to that after chemoradiotherapy, which stayed unchanged in bivariable analyses after adjustment of every other covariable. Survival of p16-negative/HPV DNA-negative locally advanced OPSCC was poor irrespective of treatment modality.
Conclusions: Survival in p16-positive locally advanced OPSCC differs depending on HPV DNA status. Radiotherapy alone can serve as a de-intensified treatment for p16-positive/HPV DNA-positive locally advanced OPSCC, but not for p16-positive/HPV DNA-negative locally advanced OPSCC.