[The efficacy of blinatumomab in the treatment of pediatric B-cell acute lymphoblastic leukemia: a multicenter study].

<b>Objective:</b> To investigate the efficacy and toxicity of blinatumomab in the first-line and second-line treatment of pediatric B-cell acute lymphoblastic leukemia (B-ALL). <b>Methods:</b> A multi-center retrospective cohort study was conducted to analyze clinical data from 323 pediatric B-ALL patients treated with blinatumomab across 14 hospitals in China from May 2021 to July 2023. Patients were divided into four groups based on the treatment phase and disease status when blinatumomab used: relapsed/refractory group, post-consolidation minimal residual disease (MRD)-positive group, early MRD-positive group, and MRD-negative group. Blinatumomab for the relapsed/refractory group was considered as second-line treatment, while the other three groups as first-line treatment. The remission rate, the MRD negativity rate after treatment, the survival rates and the incidence of severe adverse events were compared across these groups. Patients who received blinatumomab for more than 7 days were included in the efficacy analysis. Survival analysis was performed using the Kaplan-Meier method, and Log-Rank test was used to compare the survival rates among groups. <b>Results:</b> Among the 323 patients, 191 (59.1%) were male, with the age of 6.2 years. There were 117 patients in the relapsed/refractory group, 62 cases in the post-consolidation MRD-positive group group, 43 cases in the early MRD-positive group, and 101 cases in the MRD negative group. In the relapsed/refractory group, the complete remission rate and MRD negativity rate after one course of blinatumomab were 71.4% (35/49) and 81.5% (75/92) for the 49 children without complete remission and the 92 children with flow cytometry-positive MRD, respectively. In the post-consolidation MRD-positive group, the MRD negativity rates after one course of blinatumomab were 100.0% (27/27), 12/16, and 9/19 for patients with MRD positivity detected by flow cytometry, polymerase chain reaction, and next-generation sequencing, respectively. In the early MRD-positive group, the MRD negativity rates were 96.7% (29/30) and 9/9 for flow cytometry and next-generation sequencing, respectively. The 2-year overall survival rate and event-free survival rate for the 319 children evaluable for efficacy were (90.6±1.7)% and (87.6±1.9)%, respectively, with the relapsed/refractory group showing significantly lower overall survival rates and event-free survival rate compared to the other groups(<i>χ</i>²=21.40, 26.21,both <i>P</i><0.001). Grade 3 or higher adverse events occurred in 128 cases (39.6%), with hematological toxicity observed in 101 cases, while cytokine release syndrome (CRS), infection, and neurotoxicity occurred in 11, 26 and 8 cases, respectively. In addition, there were statistically significant differences in the grade 3 or higher CRS among the four groups (<i>χ</i>²=8.03, <i>P</i><0.05). <b>Conclusion:</b> Blinatumomab can clear MRD more effectively and achieve superior survival outcomes when used as first-line treatment for pediatric B-ALL, with less CRS.