This article presents analysis of recent publications on hyperleukocytosis in children with AML. The mechanisms of the development of life-threatening complications accompanying hyperleukocytosis are analyzed in detail. In this review of the literature, the authors focus on the adequacy and timing of therapy for such life-threatening complications of hyperleukocytosis as leukostasis, DIC, and acute tumor lysis syndrome. The authors emphasize that in the treatment of hyperleukocytosis an important place, in addition to specific therapy, is taken by the accompanying therapy in the intensive care unit. The place of replacement blood transfusions and leukopheresis as part of the accompanying therapy is discussed.

Background. Extramedullary infiltration (EI) is relatively common in children with acute myeloid leukemia (AML) (up to 20-25 %). However, its clinical and prognostic significance remains poorly understood.Objective: to describe clinical features and to define prognostic significance of EI in children with AML.Materials and methods. The subjects of retrospective observational study were 228 children with de novo AML. The median age was 6.6 years. All of them were treated according to the protocol AML-MM-2006 from April 2007 to June 2018.All patients with EI were divided into three cohorts according to the localization of the lesions: 1) central nervous system (CNS) involvement (CNS group), 2) other localizations apart from CNS (myelosarcomas (MS) group), 3) combined lesions (CNS + MS group).Results. EI was diagnosed in 84 patients (36.84 %) with de novo AML. Among them 47 (55.95 %) had CNS involvement, 20 (23.81 %) had MS, 15 (17.86 %) had both CNS involvement and MS. 5-year overall survival (OS) rate was slightly higher in patients with CNS involvement than in children without EI - 80 ± 12 % vs 71 ± 9 %, p = 0.26, however OS in patients with MS was significantly lower - 45 ± 16 % vs 71 ± 9 %, p <0.001. In addition, OS in high-risk patients according to the protocol AML-MM-2006 who underwent allogenic hematopoietic stem cell transplantation (HSCT) without EI and with MS (± CNS involvement) was similar to OS in main groups - 81 ± 11 % and 42 ± 26 % respectively, p = 0.004. 5-year event-free survival in patients with MS was also lower than in children without EI - 38 ± 16 % vs 51 ± 8 %, p = 0.011.Conclusion. Patients with MS had worse 5-year OS and EFS than children without EI according to our study. Moreover allogenic HSCT conducted in first clinical remission did not improve the survival rate. Neuroleukemia as the only EI was not an unfavorable prognostic factor in our cohort of AML patients and was more often associated with inv(16).

The prognostic role of HL in AML in children is a matter of a discussion. 185 patients were treated for AML in our center, 36 of 185 had HL (19.5%). The study was approved by the Independent Ethics Committee of the Dmitry Rogachev National Medical Research Center of Pediatric Hematology, Oncology, and Immunology. Median Le was 97 × 109 /l (50–428 ± 109 /l). Standard risk group were 4 pts, intermediate – 8, hight – 24. The most common variants were M4/M5 in FAB classification – 30 pts and genetic rearrangement – MLL in 15 of 36 pts. Thirty-five patients with HL received cytoreduction course and ADE. After that, all patients received ADE and 21 pts second part of induction – course HAM. Remission was achieved in 27 (75%) out of 36 pts. HSCT was performed in 23 pts. Thirteen out of 36 patients with HL died: 4 (30%) – due to leukostasis complications. OS for HL group was 0.56 ± 0.09, for non-HL group was 0.75 ± 0.04, p = 0.005; EFS (HL) 0.42 ± 0.09, EFS (non-HL) 0.49 ± 0.04, p = 0.026. Also, differences in I CR achievement, median of remission length and death before remission between two groups were statistically significant (p = 0.036; p = 0.028; p = 0.021 respectively). OS and EFS in patients with M4/M5 with HL > 50 ± 109 /l were better than in patients all FAB with HL > 100 ± 109 /l, OS 0.71 ± 0.1 vs OS 0.43 ± 0.1 (p = 0.012); EFS 0.54 ± 0.1 vs EFS 0.29 ± 0.1 (p = 0.038) respectively. HL significantly worsens OS and EFS in children with AML.