Statistics analysis
The analysis of differences between groups was calculated by the t test or ANOVA for continuous variables and the chi‐square test or Fisher's exact test for categorical variables. Univariate analysis of survival curves was conducted according to the Kaplan–Meier method and log‐rank test. Cox proportional hazards model was applied for multivariate analysis of the prognostic factor for survival. A two‐sided α error of 0.05 was considered the statistical significance threshold. All the statistical analyses were performed by the SPSS 25.0 software and plotted by GraphPad Prism 8.0.