 Statistical analysis Descriptive data were reported as either mean SD, median interquartile range or number and percentage. With respect to the differences between two groups, categorical variables were compared using chi-square analysis. Continuous variables were compared using Independent Sample T test for normally distributed data and Mann-Whitney U test for non-normally distributed data. For survival analyses, Kaplan-Meier estimates were generated to assess differences between groups using the log-rank test, and expressed the data as cumulative mortality curves. Statistical analysis was performed by using SPSS 16.0 Chicago, Ill, USA and PASS 11.0. Statistical significance was defined as a P value 0.05. 