Statistical analysis

All statistical analyses were conducted using SPSS version 24 software package (IBM Co., Armonk, NY, USA). Data are shown as the median (range), median (interquartile range), or number (%) of patients. The chisquare test, Fisher’s exact test, and Mann-Whitney test were used to compare data regarding the baseline characteristics and variables between subgroups. Survival analyses were performed using the Kaplan-Meier method with the differences in survival curves assessed using the log-rank test. Cox proportional hazards models were used to estimate the hazard ratios for the variables. For all analyses, two-sided tests of significance were used with a p value of less than 0.05 considered to be statistically significant.