Data analysis was performed using SPSS 14.0 (Statistical Package for the Social Sciences, Chicago, Illinois). Data were presented as number of cases, mean ± standard deviation (SD), or median with interquartile range. Categorical comparisons were performed by chi-square test using Yates's correction if indicated or by Fisher's exact test. Continuous variables were compared using the t-test or Wilcoxon test. Variables with p < 0.20 in the univariate analysis were analyzed in the multivariate analyses. We have chosen this widespread adopted cutoff because using a more traditional level (P < 0.05) might fail to identify variables known to be important. In addition, confusion variables can affect estimates even when their level of significance does not reach 0.05. Kaplan-Meier survival curves were used to analyze the survival of patients. Those factors significantly associated with survival were further analyzed with the Cox proportional hazard model (method forward) adjusted by sex and age. Hazard ratio (HR) with 95% confidence interval (CI) was used to report the results. A two-sided p value < 0.05 was considered significant for all analyses.