Abstract: Objective To investigate the efficacy and prognostic factors of single⁃center CCLG⁃ALL 2018 regimen in the treatment of children with MLL⁃rearrangement acute lymphoblastic leukemia (MLL⁃r ALL). Methods A total of 19 newly diagnosed children with MLL⁃r ALL who received CCLG⁃ALL 2018 regimen in Children's Hospital Affiliated to Zhengzhou University from April 2018 to July 2022 were retrospectively analyzed. Results Among the 19 children with MLL⁃r ALL, 12 (63.2%) were males and 7 (36.8%) were females; 15 (78.9%) aged ≤1 year old, and 4 (21.1%) aged>1 year old. The median age at diagnosis was 10.2 months (range: 0.5-156.0 months). There were 18 (94.7%)  cases of BCP⁃ALL and 1(5.3%) case of T⁃ALL. MLL⁃AF4 was the most common fusion genotype (7/19). The median follow⁃up time was 19.0 months (range: 0.1-62.0 months), and 1 patient died 5 days after diagnosis, with a complete response rate of 61.1% on the 33rd day of induction chemotherapy. In total, 9 of 19 children died (47.4%), including 3 cases of treatment⁃related complications (1 case of pulmonary hemorrhage and 2 cases of severe infection). One case died of leukemia without remission, 5 cases died of recurrence with a recurrence rate of 26.3% (5/19), and all these cases were early bone marrow recurrence, with a median recurrence time of 6 months (range: 5-9 months). Kaplan⁃Meier showed that the 2⁃year overall survival (OS) and event⁃free survival (EFS) rates of 19 children were 57.9 % and 52.6%, respectively. The results of univariable analysis showed that there were significant differences in 2⁃year OS rate between the <1×10^-3 group and ≥1×10^-3 group on the 15th day of minimal residual disease (MRD), between the MLL rearrangement gene negative and non⁃negative groups on the 33rd day, and between the MLL⁃AF4 group and the non⁃MLL⁃AF4 group (all P<0.05). Multivariable analysis of Cox model showed that MLL⁃AF4 was an independent adverse prognostic factor affecting the OS in children with MLL⁃r ALL (P=0.032). Conclusions CCLG⁃ALL 2018 regimen could achieve remission in some of children with MLL⁃rearrangement, but the overall prognosis is poor, prone to recurrence and high mortality rate at recurrence. The MLL⁃AF4 rearrangement is the adverse factor affecting the treatment effect of CCLG⁃ALL 2018 regimen in children with MLL⁃r ALL.

Key words:  Acute lymphoblastic leukemia')"> Acute lymphoblastic leukemia, MLL?rearrangement, Children, Curative effect, Prognostic factor