This present study sought to analyze acute lymphoblastic leukemia (ALL) patients with hemophagocytic lymphohistiocytosis (HLH) registered in Kyushu-Yamaguchi Children's Cancer Study Group studies conducted between 1996 and 2007. Four of 357 patients, including two of 318 patients with B cell precursor acute lymphoblastic leukemia (BCP-ALL) and two of 39 of those with T cell acute lymphoblastic leukemia (T-ALL), were identified. HLH was observed more frequently in the T-ALL patients than in the BCP-ALL patients (P = 0.061). The mean age of 13.0 years at the diagnosis of leukemia in the HLH + ALL group was significantly higher than the 6.05 years observed in the remaining ALL groups (P = 0.001). A female predisposition was noted, as all four patients were female (P = 0.043). In two of four patients, the leukemic cells exhibited deletions on the long arm of chromosome 6 (P = 0.003). Three patients suffered from HLH during maintenance therapy. Parvovirus B19 infection and cytomegalovirus reactivation were identified as causes of HLH in one and two patients, respectively. All four patients are currently in complete remission, although one developed relapse of leukemia after receiving maintenance therapy. Based on the genetic analyses, non-synonymous single nucleotide polymorphisms (SNPs) in UNC13D, syntaxin 11, and STXBP2 were identified in all patients. Clinicians should therefore be aware of the risk of HLH during maintenance therapy, especially in older T-ALL patients with SNPs in familial HLH causative genes.

In a previous study of childhood acute lymphoblastic leukemia (ALL) by the Kyushu-Yamaguchi Children's Cancer Study Group, ALL-96, we achieved a 72.1 % 5-year event-free survival (EFS) and an 84.8 % 5-year overall survival (OS). In a subsequent study, ALL-02, we adopted a vincristine dexamethasone (VCR/DEX) pulse regimen as maintenance therapy in the context of the ALL-96 study using the same risk classification and treatment schedule. A total of 156 pediatric cases of ALL were treated with ALL-02. All of the patients were classified as standard-risk or high-risk. Risk stratification was based on white cell counts, immunophenotype, the presence of central nervous system (CNS) disease at diagnosis, organomegaly, and early treatment response (day 14 bone marrow status). The 7-year EFS and OS rates were 77.7 % (95 % CI 70.6-84.8 %) and 89.5 % (95 % CI 84.6-94.4 %), respectively. CNS 3 status [hazard ratio (HR) = 5.0, p = 0.009] and high white blood cell count at diagnosis (HR = 2.6, p = 0.047) were risk factors for poor EFS in multivariate analysis. Our strategies to categorize patients into two risk groups, and to treat with a VCR/DEX pulse were feasible and reasonably effective treatments for pediatric ALL.

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There were no differences in the EFS between the different maintenance therapies in each risk group; however, grade IV liver toxicity occurred more often in the patients receiving 6-MP/MTX with VCR and DEX therapy than in patients receiving LSA2L2.