Prognostic Role of Adjuvant Radiotherapy in Patients With pT1-2N1-2b Oropharyngeal Squamous Cell Carcinoma

ImportanceThe necessity of adjuvant radiotherapy in patients with pT1-2N1-2b oropharyngeal squamous cell carcinoma (OPSCC) remains unclear.ObjectiveTo examine the prognostic role of adjuvant radiotherapy in patients with either p16-positive or p16-negative pT1-2N1-2b OPSCC.DesignRetrospective study.SettingSurveillance, Epidemiology, and End Results database.ParticipantsPatients diagnosed between 2010 and 2015 with either p16-positive or p16-negative T1-2N1-2bM0 OPSCC who received primary surgery with neck dissection with or without adjuvant radiotherapy were screened for inclusion.InterventionPrimary surgery with neck dissection with or without adjuvant radiotherapy.Main Outcomes and MeasuresOverall survival (OS) and disease-specific survival (DSS) were main outcomes. The overlap propensity score weighting method was applied to account for known confounding. Cox regression analysis and weighted cox regression analysis were used to calculate the hazard ratio (HR) and 95% confidence interval (CI).ResultsA total of 247 patients with p16-negative OPSCC (median follow-up duration: 39 months; 3-year OS: 84.9%; 3-year DSS: 89.5%) and 1175 patients with p16-positive OPSCC (median follow-up duration: 35 months; 3-year OS: 95.3%; 3-year DSS: 96.7%) were included. Adjuvant radiotherapy was associated with improved OS [weighted HR (95% CI): 0.37 (0.17-0.79)] and DSS [weighted HR (95% CI): 0.34 (0.13-0.88)] in pT1-2N1-2b p16-negative OPSCC. No prognostic role of adjuvant radiotherapy was observed in pN1 subgroup of p16-negative OPSCC [weighted HR (95% CI) for OS: 0.89 (0.20-4.06); weighted HR (95% CI) for DSS: 1.12 (0.19-6.71)]. Adjuvant radiotherapy was associated with improved OS [weighted HR (95% CI): 0.34 (0.18-0.62)] and DSS [weighted HR (95% CI): 0.30 (0.14-0.64)] in pT1-2N1-2b p16-positive OPSCC. Subgroup analyses of p16-positive OPSCC, including pN1, pN2a-2b, and positive lymph nodes ≤4 subgroups, supported that adjuvant radiotherapy had positive prognostic role.Conclusions and RelevanceConsistent with the National Comprehensive Cancer Network guidelines, patients with pT1-2N2a-2b OPSCC should receive adjuvant radiotherapy (regardless of p16 status), while patients with pT1-2N1 p16-negative OPSCC could consider omitting adjuvant radiotherapy. Patients with pT1-2N1 p16-positive OPSCC may benefit from adjuvant radiotherapy.