Statistical analysis
REGRESSION
Primary endpoints were assessed using Kaplan–Meier survival analysis and the log-rank test. Secondary endpoints were assessed using bivariate and multivariate analyses as appropriate. Categorical variables are presented as absolute frequencies. Demographic and clinical variables are presented as medians, ranges, means, and standard deviations according to the distribution. Binomial negative regression test, chi-square test and Fisher exact test were used as bivariate tests, as appropriate, and Cox regression by forward stepwise selection was used as a multivariate test. All tests were conducted at 95% confidence intervals and at a significance level of 5%. Statistical analyses were performed using SPSS version 20 (SPSS Inc., Chicago, IL, USA).