STATISTICAL METHODS:
The descriptive analysis included the absolute and relative frequency for categorical variables. Comparison between groups was carried out using the Chi-square test or Fisher’s exact test. Variables for the survival analysis were age, primary site, metastatic site, baseline LDH, chemotherapy regimen, response to chemotherapy and surgery. The survival curve was estimated for each variable using the Kaplan-Meier method. The comparison between curves was obtained by the log-rank test. The Cox regression model was used to assess the effect of the variables on survival (multivariate analysis to calculate hazard ratios), which included variables with the following characteristics according to the Kaplan-Meier analysis with a significant difference (p<0.05). The level of significance established for all analyses was 5%. All analyses were performed using the software SPSS®20.0 for Windows (Statistical Package for Social Sciences, IBM, USA).