Statistical analysis
All statistical analyses were administrated with the Statistical Package for Social Sciences® 25.0 software for Mac OS X® (IBM, Chicago, USA). Utilizing this program, descriptive and comparative statistics (i.e., χ2-test, t-test, Mann-Whitney U-test) were performed. The significance tests were performed bilaterally. The data of the interval-scaled variables are expressed as mean ± standard deviation. Multivariate data analysis was performed using Cox proportional hazards regression to determine the perioperative risk factors for clinical outcomes in the two endpoints of this study. Receiver-operating characteristic (ROC) analysis was performed to evaluate the accuracy of the statistical performance for some variables. Statistical correlation analysis was performed using Spearman’s correlation coefficient. Statistical significance was set at P < 0.05.