Statistical analysis
Continuous variables were tested for normality with the Kolmogorov-Smirnov and Shapiro Wilk tests. The values are expressed either as mean ± standard deviation (SD) or median, and 25 and 75 percentiles. The categorical data are presented as absolute values and percentages and were tested using Pearson χ2 test and Fischer’s Exact Test. The comparison between groups was performed using the Kruskal Wallis test or Pearson χ2 test and Fischer’s Exact Test, as appropriate. Event-free survival and patient survival analysis was conducted according to the Kaplan-Meier product-limit estimates, and patient subgroups were compared using a two-sided log-rank test.
A Cox-Regression analysis was conducted to evaluate the association of each clinically or statistically significant (p<0.1) variable with the outcome (event-free survival).
A scoring system was derived from the Cox-Regression analysis to predict the outcome probability (recurrence/death) according to the number of factors presented by the patient in the pre-transplant period.
The area under the receiver operating characteristic curve (AUC ROC) was the tool used to evaluate the association of AFP reduction with the outcome (event-free survival). Therefore, AUC ROC ranges from 0 to 1, with 1 corresponding to a perfect score. AUC ROC ≤ 0.7 are considered to have very little predictive ability. The level of statistical significance adopted was P ≤ 0.05. All analyses were performed using the SPSS 21.0 statistical package (IBM, Inc., Chicago, IL, USA).