STATISTICAL ANALYSIS
Statistical analysis was performed using SPSS Version 16 software (IBM, Armonk, New York). Data were expressed as median and range (minimum-maximum) for numerical data, number and percentage for categorical data. Comparisons between groups were calculated using nonparametric Mann–Whitney test for numerical data and χ2 test for categorical data. Survival analysis was done using Kaplan-Meier log-rank univariate analysis.