Clinical outcomes following observation, post-operative radiation therapy, or post-operative chemoradiation for HPV-associated oropharyngeal squamous cell carcinomas

Intermediate and high-risk features (IRFs/HRFs) for locoregional recurrence following initial surgery for oropharyngeal SCCs (OP-SCCs) were defined prior to the known association of HPV with OP-SCC. There are limited reports on practice patterns and outcomes associated with post-operative radiation therapy (PORT) or chemoradiation (POCRT) for HPV-associated OP-SCCs.The National Cancer Database was queried for patients with HPV-associated OP-SCCs managed initially with surgery with IRFs or HRFs. IRFs were defined as pT3/T4 disease, pN1-3 disease, and lymphovascular space invasion, and HRFs as positive margins and extranodal extension (ENE). Patients were stratified into no adjuvant therapy, PORT, or POCRT arms. Kaplan-Meier analysis was utilized for comparison of overall survival (OS) between treatment arms followed by a Cox multivariate (MVA) proportional-hazards model and propensity score analyses with inverse probability treatment weighting (IPTW).We identified 6,301 patients; 51.2% had IRFs only and 48.8% had HRFs. Regarding treatment, 25.5%, 38.2%, and 36.3% of patients received no RT, PORT, and POCRT, respectively. Patients with IRFs who did not receive RT or CRT had inferior 8-year OS (81.1% vs. 87.8%; p < 0.001) that remained significant on IPTW MVA (hazard ratio (HR) = 1.69 (95% CI: 1.27-2.24; p < 0.001). Among patients with HRFs, 8-year OS was not significantly different between patients receiving PORT vs. POCRT (77.3% vs. 79.2%; p = 0.22) that remained insignificant on IPTW MVA (HR = 0.91(0.72-1.17); p = 0.48).A significant proportion of HPV-associated OP-SCC patients with IRFs or HRFs did not receive PORT, which was associated with inferior OS. We did not demonstrate with statistical power that POCRT vs. PORT was associated with superior OS in patients with HRFs, though prospective studies are warranted.