Abstract： Objective:To investigate the clinical characteristics and prognostic factors of TCF3-PBX1 fusion gene-positive childhood B-cell precursor acute lymphoblastic leukemia (B-ALL).Methods:The clinical data of 1 287 newly diagnosed children with B-ALL who were admitted to five hospital in Fujian province (Fujian Medical University Union Hospital, the First Affiliated Hospital of Xiamen University, Zhangzhou Affiliated Hospital of Fujian Medical University, Quanzhou First Hospital Affiliated to Fujian Medical University, Nanping First Hospital of Fujian Province) from April 2011 to December 2020 were retrospectively analyzed. According to the results of TCF3-PBX1 fusion gene testing, all the patients were divided into TCF3-PBX1-positive group and TCF3-PBX1-negative group. The clinical characteristics, early treatment response [minimal residual disease (MRD) at middle stage and end of induction chemotherapy] and long-term efficacy [overall survival (OS) and event-free survival (EFS)] of the patients in both groups were compared. Kaplan-Meier method was used for survival analysis. The prognostic factors of TCF3-PBX1-positive B-ALL were analyzed by using Cox proportional hazards model. Among 83 children with TCF3-PBX1-positive B-ALL, the treatment regimens, risk stratification and efficacy evaluation of 62 cases were performed by using Chinese Children's Leukemia Group (CCLG)-ALL 2008 regimen and 21 cases were performed by using Chinese Children's Cancer Group (CCCG)-ALL 2015 regimen, and the efficacy and incidence of serious adverse events (SAE) between the two groups compared.Results:Among 1 287 B-ALL patients, 83 patients (6.4%) were TCF3-PBX1-positive. The proportion of patients with initial white blood cell count (WBC)≥50×10 9/L in the TCF3-PBX1-positive group was higher than that in the TCF3-PBX1-negative group, while the proportions of patients with MRD ≥1% on induction chemotherapy day 15 or day 19, and MRD ≥0.01% on induction chemotherapy day 33 or day 46 in the TCF3-PBX1-positive group were lower than those in the TCF3-PBX1-negative group (all P < 0.05). Univariate Cox regression analysis showed that MRD ≥1% on induction chemotherapy day 15 or day 19 and TCF3-PBX1 ≥0.01% on induction chemotherapy day 33 or day 46 were risk factors for OS and EFS (all P < 0.05). Multivariate analysis showed that MRD ≥1% on induction chemotherapy day 15 or day 19 was an independent risk factor for OS ( HR = 10.589, 95% CI 1.903-58.933, P = 0.007) and EFS ( HR = 10.218, 95% CI 2.429-42.980, P = 0.002). TCF3-PBX1≥0.01% on induction chemotherapy day 33 or day 46 was an independent risk factor for EFS ( HR = 6.058, 95% CI 1.463-25.087, P = 0.013) but not for OS ( HR = 3.550, 95% CI 0.736-17.121, P = 0.115). The 10-year EFS and OS rates of the TCF3-PBX1-positive group were 84.6% (95% CI 76.9%-93.1%) and 89.1% (95% CI 82.1%-96.6%), and the differences between the two groups were not statistically significant (both P > 0.05). Among 80 children who received standardized treatment, compared with children who were treated with CCLG-ALL 2008 regimen, the incidence of infection-related SAE was lower in children who were treated with CCCG-ALL 2015 regimen [0 (0/21) vs. 20.3% (12/59), χ2 = 5.22, P = 0.022], but there were no statistical differences in treatment-related mortality, relapse rate, EFS and OS between the two groups (all P > 0.05). Conclusions:Children with TCF3-PBX1-positive B-ALL have a good prognosis, and MRD≥1% at middle stage of induction chemotherapy and TCF3-PBX1≥0.01% at the end of induction chemotherapy may be influencing factors for poor prognosis. CCCG-ALL 2015 regimen can reduce infection-related SAE while achieving good efficacy.