Although typically associated with a favorable prognosis, a minority of human papillomavirus (HPV)-related (+) oropharyngeal cancers recur after chemoradiation. We postulated that a minor HPV-negative tumor subfraction may be responsible for recurrences of HPV+ oropharyngeal cancer.

Paired untreated primary and recurrent tumor specimens were identified for 37 patients with oropharyngeal cancer who received definitive chemoradiotherapy at our institution. Concordance in HPV/p16 expression between primary and recurrent tumors was assessed.

Among 31 patients with HPV+/p16+ primary tumors, 30 (97%) retained evidence of both HPV and p16 expression at recurrence (27 HPV+/p16+; 3 HPV+/p16-partial). One (3%) initially HPV+/p16+ patient developed an HPV-negative/p16-negative lung squamous cell carcinoma (SCC), representing either a discordant oropharyngeal cancer metastasis or second primary tumor.

HPV-related oropharyngeal cancers retain HPV+/p16+ expression at recurrence. Our results fail to provide evidence that a minor HPV-negative tumor subfraction is responsible for biologically aggressive behavior of HPV+ oropharyngeal cancer that recurs after chemoradiation.