Statistical analysis
All data were described using standard summary statistics. Survival estimates were obtained using the Kaplan-Meier method and presented with corresponding 95% confidence intervals (CI). Patients who were less than 3 years old at time of surgery were analyzed separately in the survival analyses, as we considered them a special group with different presentation and outcomes. Progression-free survival (PFS) was defined as time from registry at INCA to the date of first relapse or progression of disease, death, secondary malignancy, or date of last follow-up. Overall survival (OS) was measured as time from registry at INCA to date of death or last follow up. Log-rank tests were used to compare survival between patient groups. P-values were two-sided and those less than 0.05 were considered statistically significant. Statistical analyses were performed in the R statistical package (R Founding for Statistical Computing, Vienna, Austria) using thesurvival and survminer packages.