Statistical analysis
SPSS 22.0 software was used for statistical analysis. The data are presented as means ±SD. One-way ANOVA was used for comparisons among the four groups. A two-sided P -value < 0.05 was considered statistically significant. The DFS and OS were graphing using GraphPad Prism 7.00, calculated using the Kaplan Meier method, and survival curves were compared using log-rank test.