[Clinical Characteristics and Prognosis of MLL Rearranged Childhood Acute Lymphocyte Leukemia]

AbstractObjective: To investigate the clinical characteristics and prognostic factors in childhood acute lymphoblastic leukemia with MLL gene-rearrangement-positive (MLL-r⁺ ALL).

The clinical data of 1 414 newly diagnosed children with ALL admitted to five hospital in Fujian province from April 2011 to December 2020 were retrospectively analyzed. The clinical characteristics and efficacy of MLL-r⁺ and MLL-r^- subgroup were compared. The prognostic factors of MLL-r ALL were analyzed by COX regression model.

Among all children with ALL, the proportion of patients aged less than 1 year old was 1.8%, and the detection rate of MLL-r⁺ was 3.4% (48/1 414). The positive detection rate of MLL-r in the age groups <1 year old, and ≥1 year old and ≤14 years old was 38.5% (10/26) and 2.7 (38/1 388), respectively, the difference was statistically significant (P<0.000). Compared with MLL-r^- group, the MLL-r⁺ group had a higher proportion of patients with age <1 year, white blood cell (WBC) count ≥50×10⁹/L, combined central nervous system leukemia (CNSL) and testicular leukemia(TL), while MRD <0.01% on d 33 or d 46 of induction chemotherapy was lower (all P<0.05). The expected 10-year event free survival(EFS) rate and overall survival(OS) rate of the MLL-r⁺ group were significantly lower than those of the MLL-r^- group （EFS： 49.9% vs 77.0%； OS: 55.3% vs 82.9%， P<0.05). COX regression model analysis showed that age <1 year, minimal residual disease (MRD) ≥0.01% on d 33 or d 46 of induction chemotherapy were independent risk factors for worse OS and EFS in MLL-r⁺ ALL patients (all P<0.05).

Age <1 year old, high WBC, concomitant CNSL and TL are more common in children with MLL-r⁺ ALL at initial diagnosis, with poor early treatment response and long-term prognosis. Age <1 year old at initial diagnosis and MRD positive after induction chemotherapy may be risk factors for poor prognosis.