Demographics and clinical characteristics
We examined data on 307 pediatric AML patients between 2005 and 2015 and 81 patients (26.38%) with hyperleukocytosis. According to the WBC count, the baseline demographic and clinical characteristics of AML patients with and without hyperleukocytosis compared in Table 1. The proportion of males in the two groups was 55.31% and 61.73, respectively. Hyperleukocytosis at onset was high in patients with the M5 subtype (n=41, 50.62%) in the FAB classification, whereas without hyperleukocytosis was high in patients with FAB M2 subtype (n=126, 55.75%). The proportion of intermediate cytogenetics and FMS-like tyrosine kinase 3-internal tandem duplication (FLT3-ITD) was higher in patients with hyperleukocytosis than without hyperleukocytosis (54.32% vs. 32.30%, P<0.001; 19.75% vs. 3.98%, P <0.001). The proportion of favorable cytogenetics and core binding factor acute myeloid leukemia (CBF-AML) was lower in patients with hyperleukocytosis than without hyperleukocytosis (18.52% vs. 44.69%, P<0.001; 22.22% vs. 48.23%,P <0.001) (Table 1). The baseline demographic and clinical characteristics of hyperleukocytosis subgroups compared in Table 1S.
Impact of hyperleukocytosis on treatment response
Overall mortality was significantly higher in patients with hyperleukocytosis than in patients without hyperleukocytosis (50.62% vs. 35.84%,P =.020), while the CR rate after induction was similar between the two groups (75.31% vs. 76.99%,P =.759) (Table 2). Table 2S illustrates that the CR rate was significantly higher in favorable/intermediate cytogenetics in the WBC count 50-100×109/L subgroup than the WBC count ≥100×109/L subgroup (92.31% vs. 63.64%,P =.013), and yet CR rate was no significant difference between the two subgroups in other circumstances. To our surprise, there was no significant difference in mortality rate between the two subgroups regardless of sex, age, cytogenetics or specific molecular alterations.