Abstract: Objective To investigate the expression of fusion genes and clinical characteristics in children with acute lymphoblastic leukemia (ALL). Methods The clinical data of 341 newly diagnosed ALL children patients admitted to Henan Children's Hospital from January 2018 to December 2021 were enrolled and retrospectively analyzed. The patients were divided into positive group and negative group according to the detection of fusion genes, and the clinical characteristics, complete response rate, recurrence rate and mortality as well as other indicators were compared among different groups. Results The positive detection rate of fusion genes in 341 children with ALL was 48.1% (164/341), with a total of 15 fusion genes were detected, including TEL⁃AML1, KMT2A rearrangement, E2A⁃PBX1, BCR⁃ABL1, MEF2D rearrangement, SIL⁃TAL1, etc. There was a statistically significant difference in fusion gene expression among different age groups (P<0.001) , with KMT2A rearrangement and MEF2D rearrangement more common in the <1 years old group and the >10 years old group, respectively. Hyperleukopenia was more common in children with KMT2A rearrangement+, BCR⁃ABL1+, MEF2D rearrangement+ and SIL⁃TAL1+, and the children patients with latter three types were more prone to central nervous system involvement. KMT2A rearrangement (P<0.001), BCR⁃ABL1 (P=0.001), and MEF2D rearrangement (P=0.001) were more common in the high⁃risk patients. The detection rate of gene mutation in the fusion gene positive group was significantly lower than that in the negative group (27.9% vs 53.6%, P<0.001). The Ph⁃like gene was only detected in children with acute B⁃lymphocytic leukemia, and the highest detection rate was found in the IK6 subtype, with 40% (8/20) of the IK6 subtype associated with BCR⁃ABL1. In the evaluation on the 33rd day and the 12th week of treatment, the complete remission rate of minimal residual desease (MRD) detected by polymerase chain reaction in BCR⁃ABL1+ ALL patients was lower than that of MRD detected by flow cytometry at the corresponding time point (P<0.05). The recurrence rate of the fusion gene positive group was significantly higher than that of the negative group (P<0.001), while there was no statistically significant difference in mortality between the two groups (P=0.080). The highest recurrence and mortality were observed in the KMT2A rearrangement+ group. Conclusions Children with newly diagnosed ALL exhibit significant differences in clinical characteristics, treatment response rate, recurrence rate, and mortality. Monitoring MRD during treatment is an important basis for assessing risk stratification and predicting prognosis.

Key words: Acute lymphoblastic leukemia, Children, Fusion gene, Therapeutic response, Prognosis