Statistical analyses were mainly conducted by SPSS software (Version 22, IBM). Chi-square test and rank sum test (Mann-Whitney U test) were used to analyze the unordered categorical variable and ranked data, respectively. Student's t-test was used to analyze the continuous data, if homogeneity of variance and normal distribution. Otherwise, rank sum test was used. Logistic regression was applied in multivariate correlation analysis. Kaplan-Meier and life-table methods were used to calculate the cumulative survival rates. Log-rank test and Cox's proportional hazard regression model were conducted for univariate and multivariate survival analyses, respectively. Prism 5 for Windows (Version 5.01, GraphPad Software) was used to draft the figure of Kaplan-Meier curve. Nomograms and calibration curves were performed through R for Windows (Version 3.2.0, R Foundation for Statistical Computing) with the package of Regression Modeling Strategies (rms), in which the variables were selected according to the model by Akaike information criterion in a stepwise algorithm. Comparison between the nomogram and TNM stage was performed with the package of Harrell Miscellaneous (Hmisc) and was evaluated by C-index meaning that the larger C-index, the more accurate was the prognostic prediction. Two-sided p value less than 0.05 was considered as statistical significance.