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Published on: October 17, 2025
Nationwide survey of pediatric hypodiploid acute lymphoblastic leukemia in Japan
Sae Ishimaru1,2, Yasuhiro Okamoto3, Chihaya Imai4
1Department of Pediatric Oncology, National Cancer Center Hospital, Tokyo, Japan.
Insights
Pediatric acute lymphoblastic leukemia (ALL) with fewer than 44 chromosomes has poor outcomes in Japanese children. Patients with 44 chromosomes showed a better prognosis, warranting further international research for improved treatment strategies.
Area of Science:
- Pediatric Oncology
- Hematology
- Genetics
Background:
- Ploidy is a critical prognostic indicator in pediatric acute lymphoblastic leukemia (ALL).
- Hypodiploid ALL in children is associated with unfavorable outcomes, even with intensive chemotherapy.
- Limited research exists on hypodiploid ALL specifically within the Japanese pediatric population.
Purpose of the Study:
- To investigate the clinical characteristics and outcomes of pediatric hypodiploid ALL in Japanese children.
- To analyze survival rates based on chromosome counts in hypodiploid ALL.
- To identify prognostic factors and potential therapeutic targets for this subgroup.
Main Methods:
- Retrospective analysis of clinical data from 117 pediatric hypodiploid ALL patients.
- Data collected from prospective multicenter trials in Japan (1997-2012).
- Classification of patients based on chromosome counts: 45, 44, and fewer than 44 chromosomes.
Main Results:
- Significant differences in 5-year overall survival rates were observed: 86.0% (45 chromosomes), 87.5% (44 chromosomes), and 62.5% (<44 chromosomes) (P=0.037).
- Patients with 44 chromosomes demonstrated favorable outcomes, with 7 of 8 alive and 5 in complete remission without HSCT.
- Patients with <44 chromosomes had a high relapse rate (5/8), despite good initial response to prednisolone; only 1 of 4 who underwent HSCT survived.
Conclusions:
- Pediatric ALL patients with fewer than 44 chromosomes in Japan experience poor outcomes, consistent with international findings.
- A subset of patients with 44 chromosomes exhibited a better prognosis than previously reported, suggesting potential for improved management.
- International collaboration is crucial for further research to enhance treatment strategies and outcomes for pediatric ALL patients with fewer than 44 chromosomes.
Background:
Ploidy is a highly significant prognostic factor for pediatric acute lymphoblastic leukemia (ALL). Children with hypodiploid ALL have poor outcomes despite current intensive chemotherapy. Little has been investigated with regard to hypodiploid ALL in Japanese children.
Methods:
We retrospectively collected clinical data on hypodiploid ALL cases from the registries of prospective multicenter trials conducted by the four independent clinical study groups in Japan between 1997 and 2012.
Results:
A total of 117 ALL patients with hypodiploidy were analyzed in this study. There were 101, eight, and eight patients with 45, 44, and fewer than 44 chromosomes, respectively. The 5 year overall survival rates differed significantly: 86.0%, 87.5%, and 62.5% for patients with 45, 44, and fewer than 44 chromosomes, respectively (P = 0.037). Of the eight patients with 44 chromosomes, seven were alive, including five patients who maintained complete remission without undergoing hematopoietic stem cell transplantation (HSCT). Of the eight patients with fewer than 44 chromosomes, six were good responders to prednisolone and none had induction failure, but the relapse rate was high (5/8). No patients had central nervous system relapse. Four patients underwent HSCT after relapse, but only one survived.
Conclusions:
Outcomes of Japanese ALL patients with fewer than 44 chromosomes were poor, as previously reported in other countries. Although the sample size was small, patients with 44 chromosomes had better prognoses than those previously reported. Further studies including international collaboration are needed to improve outcomes for pediatric ALL patients with fewer than 44 chromosomes.
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