Statistical analyses

All statistical analyses were performed using IBM SPSS Statistics for Windows, version 25. (IBM Corp., Armonk, NY, USA). Continuous variables are expressed as median with the interquartile range, whereas categorical variables are expressed as numbers (%). Significant differences between the two categorical variables were analysed using the Chi-square and Fisher’s exact tests. The correlation coefficient (r) between the two variables was obtained using either the Pearson correlation analysis or the univariable linear regression analysis. Also, multicollinearity was evaluated using the univariable linear regression analysis. The optimal cut-off was extrapolated by performing the receiver operator characteristic (ROC) curve analysis and one value having the maximised sum of sensitivity and specificity was selected. Comparison of the cumulative survivals rates between the two groups was analysed by the Kaplan–Meier survival analysis with the log-rank test. The multivariable Cox hazard model using variables with statistical significance in the univariable Cox hazard model was conducted to appropriately obtain the hazard ratios (HRs) during the considerable follow-up duration. p-values less than 0.05 were considered statistically significant.