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.