Effect of Prognostic Factors of Postoperative Radiotherapy in Oral Squamous Cell Carcinoma: A SEER-Based Study

Objective: The treatment of oral squamous cell carcinoma (OSCC) is dominated by surgery and radiochemotherapy, but its prognosis is still unsatisfactory, with around five tenths of 5-year survival. This study aimed to assess the prognosis of OSCC patients treated with surgery with and without postoperative radiotherapy. Study Design: Retrospective study. Methods: The clinicopathological information and follow-up datasets on patients with OSCC (T_1-4 and/or N+) registered from 2010 to 2015 were downloaded from the Surveillance, Epidemiology, and End Results database. Totally 7231 enrolled subjects were divided into a case group (surgery alone, n = 4167) and a control group (surgery combined with postoperative radiotherapy, n = 3064). One-to-one matching was performed by propensity score matching to make the baseline data comparable between the 2 subgroups. Multivariate Cox regression analysis was used to calculate hazard ratios (HR) of various clinicopathological features. The Kaplan-Meier method and log-rank test were used to plot the survival curves. Results: The majority of patients in case group were tumor stage I (n = 2569, 61.7%), whereas most patients in control group were stages III to IV (n = 2360, 77.1%). In the case group, the 1-, 3-, and 5-year overall survival (OS; 76%, 59.5%, 53.7%) were significantly lower than those of the control group (85.1%, 64.1%, 55.8%; P < .0001). Similarly, the 1-, 3-, and 5-year cancer-specific survival (CSS) of the case group (80.2%, 66.6%, 63.3%) were significantly lower than those of the control group (87.2%, 69.3%, 63.9%, respectively; P < .0001). Cox multivariate analysis indicated that age, differentiation, clinical stage, and tumor-node-metastasis stage affected the prognosis of OSCC patients, while postoperative radiotherapy was a protective factor (OS: HR = 0.649, P < .001; CSS: HR = 0.702, P < .001). Conclusions: Postoperative radiation was an independent protective factor, hence, the combination of surgery plus radiotherapy is more beneficial for the survival of patients with OSCC, particularly for advanced cases.