CD9 and esophageal squamous cell carcinoma: Survival curve analysis showed that there were no significant differences in overall survival (OS), disease-specific survival (DSS), and progression free interval (PFI) between the CD9 high and low expression groups in ESCC patients and non-radiotherapy patients; However, among ESCC patients receiving radiotherapy, the OS (P=0.067), DSS (P=0.067) and PFI (P=0.179) of the CD9 low expression group showed a beneficial trend.