Participants
Patients 18 years or older diagnosed with or treated for clinical T1 or T2 cancers with N0 or N1 nodal status and M0 OPSCC from 2004 to 2013 were eligible for inclusion in the study. Exclusion criteria included histologic diagnosis other than squamous cell carcinoma, advanced clinical stage disease, cases treated with palliative intent, and cases with missing information. Patients without known HPV status were also included in the study. Patients without HPV status were included in this study due to the overwhelming number (78%) of patients within the NCDB lacking HPV status.