 Normally distributed variables are expressed as means SDs. Statistical significance is set at P0.05. All statistical analyses are performed with SAS statistical software. Comparisons between two groups are assessed with the students unpaired t test and Mann-Whitney test. Differences between more than two groups are analyzed by ANOVA ANOVA using one-way ANOVA. Survival analyses are made with the Kaplan-Meier survival curve and the Cox proportional hazard model. 