[Clinical Characteristics and Prognosis of Children with Hypodiploid B-cell Precursor Acute Lymphoblastic Leukemia].

Objective: To analyze the clinical characteristics and prognosis of children with hypodiploid B-cell precursor acute lymphoblastic leukemia (BCP-ALL).

Methods: The clinical data of 1 287 children with BCP-ALL admitted to five hospital in Fujian province from April 2011 to December 2020 were retrospectively analyzed. According to the results of chromosome karyotype, all the patients were grouped into hypodiploid subgroup and non-hypodiploid subgroup. The clinical characteristics, early treatment response ［minimal residual disease (MRD) on middle stage of induction chemotherapy and end of induction chemotherapy］ and long-term efficacy ［overall survival (OS) and event-free survival (EFS)］ were compared. The prognostic factors of hypodiploid BCP-ALL were further explored.

Results: Among 1 287 BCP-ALL patients， 28 patients (2.2%) were hypodiploid BCP-ALL. The proportion of patients with white blood cell count （WBC）≥50×10⁹/L in the hypodiploid subgroup was significantly higher than that in the non-hypodiploid subgroup (P =0.004), while there was no statistically significant difference in gender ratio, age group at initial diagnosis, and early treatment response between the two groups (all P >0.05). The 5-year EFS and OS rate of the hypodiploid subgroup were 75.0%(95%CI ：66.8%-83.2%) and 77.8%(95%CI ：69.8%-85.8%), respectively, which were lower than those of non-hypodiploid subgroup ［EFS: 79.6%(95%CI ：78.4%-80.8%); OS: 86.4%(95%CI ：85.4%-87.5%)］, but the difference was not statistically significant (all P >0.05). Further subgroup analysis by risk stratification showed that the 5-year EFS and OS rates of the hypodiploid subgroup were significantly lower than those in the low-risk (LR) group ［LR group EFS: 91.4% (95%CI ：88.4%-93.6% ), P < 0.001; OS: 94.7% (95%CI ：92.1%-96.4%), P < 0.001］ ; it was similar to that of BCP-ALL children stratified into intermediate-risk (IR) excluding hypodiploid ［IR group EFS: 79.4%(95%CI ：74.9%-83.2%), P =0.343; OS: 87.3%(95%CI ：83.6%-90.2%), P =0.111］; while was higher than that of EFS in HR group, but the difference was not statistically significant ［HR group EFS: 58.7%(95%CI ：52.6%-64.8%), P =0.178. OS: 69.9%(95%CI ：63.5%-75.4%), P =0.417］. Univariate analysis showed that gender, age, white blood cell count, and MRD on middle stage of induction chemotherapy had no significant impact on OS and EFS; chromosome count< 40 was a risk factor for lower OS (P =0.026), but has no significant effect on EFS; MRD≥0.01% after induction therapy was a risk factor for lower OS and EFS (P =0.002, and 0.001, respectively).

Conclusion: Children with hypodiploid BCP-ALL have an intermediate prognosis, and MRD ≥0.01% after induction chemotherapy may be a risk factors for poor prognosis.