With the markedly increased cure rate for children with newly diagnosed pediatric B-cell acute lymphoblastic leukemia (B-ALL), relapse and refractory B-ALL (R/R B-ALL) remain the primary cause of death worldwide due to the limitations of multidrug chemotherapy. As we now have a more profound understanding of R/R ALL, including the mechanism of recurrence and drug resistance, prognostic indicators, genotypic changes and so on, we can use newly emerging technologies to identify operational molecular targets and find sensitive drugs for individualized treatment. In addition, more promising and innovative immunotherapies and molecular targeted drugs that are expected to kill leukemic cells more effectively while maintaining low toxicity to achieve minimal residual disease (MRD) negativity and better bridge hematopoietic stem cell transplantation (HSCT) have also been widely developed. To date, the prognosis of pediatric patients with R/R B-ALL has been enhanced markedly thanks to the development of novel drugs. This article reviews the new advancements of several promising strategies for pediatric R/R B-ALL.

A 3-year-old male child, who presented with fever for 4 days, was admitted to our hospital. The blood count analysis showed elevated white blood cells (151 x10 9 /L), decreased hemoglobin (Hb, 55 g/L), and neutrophil and lymphocyte percentages of 7.5% and 91.3%, respectively. The peripheral blood and bone marrow smear showed that the blast percentages were 79% and 73.5%, respectively. Flow cytometry of the bone marrow identified a 79.5% abnormal cell population of nuclear cells, which was positive for HLA-DR (91.94%), CD13 (76.22%), CD33 (94.25%), CD34 (30.43%), CD38 (79.99%), CD117 (96.76%), CD123 (98.93%), and MPO (47.52%). Acute myeloid leukemia (AML) prognostic gene sequencing detected a mutation in IDH1(NM_001282386 c. 395G>A (p. R132H)), and whole-exome sequencing and RNA sequencing of hematological malignancies were also performed. The patient was diagnosed with AML (M2) and hyperleukocytosis, and was tentatively classified as at intermediate risk.

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