Statistical analysis
Continuous and categorical variables were expressed as mean ± SD and percentages, respectively. Clinical characteristics were compared using the t -test for continuous variables and theχ 2 test for categorical variables. Multivariate regression analysis models were used to estimate the adjusted hazard ratios (HRs) and 95% confidence intervals (CIs) for primary and secondary endpoints. All tests were two-tailed, and p-values <0.05 were considered statistically significant. Statistical analyses were performed using SPSS version 18 (IBM Corp., Armonk, NY, USA).