Supplementary Material for: Survival and Swallowing Function after Primary Radiotherapy versus Transoral Robotic Surgery for Human Papillomavirus-associated Oropharyngeal Squamous Cell Carcinoma

Introduction: To investigate the impact of primary transoral robotic surgery (TORS) versus radiotherapy (RT) on progression-free survival (PFS), overall survival (OS), and 1-year swallowing function for patients with early-stage HPV-associated orophagyneal squamous cell carcinoma (OPSCC). Methods: Patients with stage I-II (AJCC 8th Edition) HPV-associated OPSCC treated with TORS followed by risk-adapated adjuvant therapy or (chemo)radiotherapy between 2014-2019 were identified. PFS, OS, and swallowing outcomes including gastrostomy tube (GT) use/dependence, and Functional Oral Intake Scale (FOIS) change over 1 year were compared. Results: 167 patients were analyzed: 116 treated with TORS with or without adjuvant RT, 51 treated with RT (50 chemoRT). The RT group had more advanced tumor/nodal stage, higher comorbidity, and higher rates of concurrent chemotherapy. There were no differences in 3-year PFS (88% TORS v. 75% RT) or OS (90% v. 81%) between groups, which persisted after adjusting for stage, age and comorbidity. GT use/dependence rates were higher in the RT group. Mean (SD) FOIS scores in the TORS group were 6.9 (0.4) at baseline and 6.4 (1.0) at 1-year, compared with 6.7 (0.6) and 5.6 (1.7) for the RT group. Only clinical nodal stage was found to be significantly associated with FOIS change from baseline to 1-year. Discussion/Conclusion: There were no differences in PFS or OS between patients treated with primary TORS or RT for early-stage HPV-associated OPSCC. Clinical N2 status is associated with FOIS change at 1-year and may be the major factor affecting long-term swallowing function, irrespective of primary treatment modality.