Overall survival
Pediatric patients enjoyed better OS than adults (adults 59.5%±5.4% vs. children 83.2%±4.9%, P=0.001, figure 1C1). The survival benefit in children was also observed at 2 year interim (adults 56.5%±5.5% vs. children 77.0%±5.7%, P=0.005, supplemental figure 1C). There was no difference in OS between the two groups when consolidation regimens were taken into consideration (MDAC-based regimen: children 88.2%±5.5% vs. adults 84.0%±7.3%, P=0.575, figure 1C2; SDAC-based regimen: children 60.0%±12.6% vs. adults 45.0%±7.9%, P=0.277, figure 1C3).
By multivariate analysis, both EML (with vs. without, HR 2.14, 95% CI 1.13-4.06, P=0.020) and consolidation regimens (MDAC-based vs. SDAC-based, HR 0.18, 95% CI 0.09-0.36, P<0.001) were independent risk factors for OS. C-KIT mutations (mutant vs.WT, HR 1.80, 95% CI 0.96-3.35, P=0.065) tended to be a poor factor for OS. Variables, including gender (male vs. female),  age (≥14 vs. <14 years), WBC count at the time of diagnosis (≥20×109/L vs. <20×109/L), immunphenotype including CD34, CD33, CD13, CD117, HLA-DR, CD19 and CD56 (positive vs. negative), additional chromosome abnormalities (with vs. without) and FLT3-ITD status (mutant vs. WT) did not affect the OS. Detail was shown in table 3.
Subgroup analysis revealed that adverse effects of EML (adults: with 38.7%±9.7% vs. without 68.4%±6.1%, P=0.001, figure 2C2; children: with 68.6%±18.6% vs. without 85.0%±4.9%, P=0.579, figure 2C3) and c-KIT mutations (adults: mutant 44.5%±9.7% vs. WT 68.5%±7.8%, P=0.021, figure 3C2; children: mutant 85.7%±13.2% vs. WT 82.5%±5.7%, P=0.537, figure 3C3) on OS were only observed in adult patients. The negative impact of EML and c-KIT mutations on OS was irrespective of consolidation therapies (supplemental figure 7 and 8).