Prognostic Score and Associations With Survival Improvement Offered by Radiotherapy After Surgery for Adenocarcinomas of Parotid Gland: A Population-based Longitudinal Cohort Study

Abstract

Background: Radiotherapy (RT) after surgery is a treatment option in the management of parotid adenocarcinoma, and the role of adjuvant RT for parotid adenocarcinoma remains to be clarified. The survival benefit of postoperative radiotherapy (PORT) based on prognostic risk factors needs further determination.Materials and methods: In this retrospective cohort study using SEER data, patients were divided into surgery+RT (RT group) and surgery alone (non-RT group). A prognostic risk model was constructed to stratify patients based on the survival rate. We performed a Cox regression analysis with propensity score weighting to evaluate survival benefit between the two groups. Results: We identified 2223 eligible patients with parotid adenocarcinoma, 1449 (65.2%) in the RT group and 774 (34.8%) in the non-RT group. Overall, 674 cancer-specific deaths occurred over a median follow-up of 141 months, the overall survival (OS) of RT group was better than that of non-RT group in the weighted analysis (HR=0.656, 95% CI=0.487-0.882, P=0.005). Significant survival improvements in the RT group compared with the non-RT group were only observed in patients with high risk (HR=0.647, 95% CI=0.426-0.983, P=0.041). The survival benefit of RT was significantly correlated with prognostic risk stratification (P<.001).Conclusion: In this population-based study, the patient prognostic risk stratification for parotid adenocarcinoma is associated with the magnitude of survival improvement by RT after surgery, suggesting that this risk model could provide decision guidance on comprehensive treatment strategy.