In children with acute lymphoblastic leukemia (ALL), relapse is still the leading cause of treatment failure occurring in 10–15% of cases. Overall survival after relapse plateaus at 50–60%, whereas event-free survival after second and third relapse is approximately 25% and 15%, respectively. The introduction of new immunotherapeutic agents such as blinatumomab (a bispecific T-cell engager), inotuzumab ozogamicin (InO; a CD22 + monoclonal antibody) and a chimeric antigen T-cell receptor targeted to CD19 + can significantly increase the effectiveness of treatment for relapsed ALL and help patients achieve remission faster and thus shorten the time to allogeneic hematopoietic stem cell transplantation (allo-HSCT). However, the toxicity of these novel agents and their impact on the results of allo-HSCT are still to be investigated. Our study included 55 patients with refractory B-cell ALL aged from 3 to 17 years (the median age was 10 years). The study was approved by the Independent Ethics Committee and the Scientific Council of the I.P. Pavlov First Saint Petersburg State Medical University. The patients were divided into two groups based on whether they received inotuzumab ozogamicin or not: InO+ group ( n = 24; 43.6%) and InO– group ( n = 31; 56.4%). The majority of the patients underwent haploidentical HSCT ( n = 53; 96.4%); 1 (1.8%) patient received HSCT from a matched related donor, and 1 (1.8%) from a matched unrelated donor. Conditioning regimens before allo-HSCT included: myeloablative conditioning ( n = 20; 36.4%), reduced toxicity myeloablative conditioning ( n = 5; 9.1%), and reduced intensity conditioning ( n = 30; 54.5%). Acute graft-versus-host disease prophylaxis with post-transplant cyclophosphamide was given to 49 (87.7%) recipients; 6 (12.3%) patients received seroprophylaxis. Basic combined immunosuppressive therapy consisting of a calcineurin inhibitor and an mTOR inhibitor was used in 35 (63.6%) cases, and single m-TOR inhibitor treatment was administered to 20 (36.4%) patients. In the InO+ group, 21 (87.5%) patients achieved complete remission with incomplete hematologic recovery before allo-HSCT: 5 (23.8%) patients had minimal residual disease (MRD), and 16 (76.2%) patients were MRD negative. In the InO– group, remission with incomplete hematologic recovery before allo-HSCT was achieved in 15 (48.4%) patients: 3 (9.7%) cases were MRD positive and 12 (38.7%) were MRD negative ( p = 0.003). All the patients underwent allo-HSCT, regardless of response to prior therapy. Engraftment was achieved in the InO+ group in 20 (83.3%) children in a median of 22 days (D+22) and in the InO– group in 25 (80.6%) children in a median of 19 days (D+19). Relapse was observed in 11 (55%) patients in the InO+ group and in 15 (60%) patients in the InO– group at a median of 164 days and 203 days post-transplant, respectively ( p = n. s.). In the InO+ group, 5 (31.25%) out of 16 patients in complete remission with incomplete hematologic recovery and negative MRD status relapsed after allo-HSCT within a median of 105 days (D+58 – D+169). In the InO–, 6 (50%) out of 12 patients in complete remission with incomplete hematologic recovery and negative MRD status relapsed within a median of 296 days (D+108 – D+929). Due to the small number of patients in the groups, a correlation and regression analysis showed a weak correlation between the use of InO before allo-HSCT and the occurrence of post-transplant relapse (Pearson's contingency coefficient was 0.178). Loss of the HLA haplotype at relapse was found in 1 (4.2%) patient from the InO+ group and in 2 (6.5%) patients from the InO– group ( p = n. s.). Transplant-associated thrombotic microangiopathy was diagnosed in 6 (25%) recipients in the InO+ group and in 3 (9.7%) recipients in the InO– group. Eight (32%) patients in the InO+ group and 3 (9.7%) patients in the InO– group had clinical manifestations of sinusoidal obstruction syndrome. Our study suggests the effectiveness of inotuzumab ozogamicin for the treatment of relapsed B-ALL in children before allo-HSCT. Patients with large tumor burden and high expression of CD22 + would benefit the most from therapy with InO. The application of reduced intensity conditioning regimen after CD22 + directed monoclonal antibody therapy significantly improves the overall survival rates by reducing early transplant-related mortality and makes it possible to use adoptive immunotherapy as a next line of treatment. Current allo-HSCT protocols and approaches to acute graft-versus-host disease prevention help control the development of severe complications in the early post-transplant period. Our study showed that adoptive immunotherapy via donor lymphocyte infusions can be applied in patients treated with InO who experience loss of the HLA haplotype at relapse after allo-HSCT.

Acute myeloid leukemia (AML) is the second most common type of leukemia in children and accounts for up to 20 % of all leukemias. Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is an effective, and sometimes the only therapeutic option in high-risk patients with AML. Graft-versus-host disease (GVHD) is a major complication of allo-HSCT and the main cause of transplant-related mortality. GVHD prophylaxis in children includes calcineurin inhibitors, either alone or in combination with other immunosuppressants, which can lead to grade II–IV acute GVHD in 40–85 % of cases. Alternatively, GVHD can be prevented with high-dose cyclophosphamide (50 mg/kg/day) administered on days +3, +4 after allo-HSCT, either alone or in combination with other immunosuppressive drugs depending on HLA compatibility of the donor. The aim of this study was to evaluate outcomes after allo-HSCT from an unrelated donor with GVHD prophylaxis with post-transplant cyclophosphamide (PTC) in children in their first and second remission of AML in comparison with a historical control group. We retrospectively analyzed patient outcomes after 53 first-time allo-HSCTs from HLA-matched (n = 40) and partially-matched (8–9/10) (n = 13) unrelated donors performed in pediatric patients (aged 0 to 18 years) in their 1 st or 2 nd remission of AML at the R. M. Gorbacheva Research Institute for Pediatric Oncology, Hematology and Transplantation from 2008 to 2018. The study was approved by the Independent Ethics Committee and the Scientific Council of the I. P. Pavlov First Saint Petersburg State Medical University of Ministry of Healthcare of the Russian Federation. Our group of interest included 26 patients preventively treated for GVHD with 50 mg/kg of cyclophosphamide on days +3 and +4 in combination with calcineurin inhibitors (cyclosporin A – 2 (7.7 %) patients, tacrolimus – 24 (92.3 %) patients), the mTOR inhibitor sirolimus (5 (19.2 %) patients) or mycophenolate mofetil (21 (80.8 %) patients). The historical control group was made up of 27 patients whose GVHD prophylaxis was based on antithymocyte globulin used in combination with calcineurin inhibitors (tacrolimus – 5 (18.5 %) patients, cyclosporin A – 21 (77.8 %) patients) or the mTOR inhibitor sirolimus (1 (3.7 %) patients) or methotrexate (25 (92.6 %) patients), or mycophenolate mofetil (2 (7.4 %) patients). The groups were matched for diagnosis, age, disease status before allo-HSCT, the matched-to-partially-matched donor ratio, the source of hematopoietic stem cells and conditioning regimen intensity (myeloablative conditioning regimen (MAC) or reduced intensity conditioning regimen (RIC)). The median age at the time of allo-HSCT was 8.6 (0.97–18) years in the PTC group and 6.55 (1.42–17.76) years in the historical control group. In the PTC group, 21 (80.8 %) patients were diagnosed with primary AML and 5 (19.2 %) – with secondary AML, while the historical control group included 22 (81.5 %) and 5 (18.5 %) patients with primary and secondary AML respectively. Disease status at the time of allo-HSCT: 21 (80.8 %) patients treated with PTC were in the 1 st complete clinical and hematologic remission (CCHR) and 5 (19.2 %) – in the 2 nd CCHR; among the controls, there were 19 (70.4 %) cases of the 1 st CCHR and 8 (29.6 %) cases of the 2 nd CCHR. In the PTC group, 18 (69.2 %) patients underwent allo-HSCT from 10/10 fully HLA gene-matched donors and 8 (30.8 %) – from 9/10 HLA-matched donors. In the historical control group, 19 (70.4 %) patients had allo-HSCT from 10/10 fully HLA gene-matched donors, 4 (14.8 %) – from 9/10 matched donors, and 1 (3.7 %) – from an 8/10 matched donor. In the PTC group, MAC was used in 14 (53.8 %) patients, RIC – in 12 (46.2 %) patients. In the control group, MAC and RIC were used in 14 (51.9 %) and 13 (48.1 %) patients respectively. In the group treated with PTC, hematopoietic stem cells were derived from the bone marrow in 14 (53.8 %) patients, from the peripheral blood – in 12 (46.2 %) patients. In the historical group, bone marrow was used in 13 (48.1 %) patients and peripheral blood - in 14 patients (51.9 %). The median graft cellularity (CD34+ × 10 6 /kg) in the PTC group was 4.60 (1.7–10.9) × 10 6 /kg, in the historical group – 6.60 (1.0–13.2) × 10 6 /kg. The overall and relapse-free 5-year survival rates were higher in the PTC group than in the historical control group: 83.3 % (95 % confidence interval (CI) 60.9–93.5) vs 59.3 % (95 % CI 38.6–75.0), p = 0.0327 and 76.9 % (95 % CI 55.7–88.9) vs 48.1 % (95 % CI 28.7–65.2), respectively, p = 0.0198. The cumulative incidence of grade II–IV acute GVHD and grade III–IV acute GVHD by day +125 and of moderate and severe chronic GVHD, and the 2-year transplant-related mortality were significantly lower in the PTC group compared to the controls: 15.4 % (95 % CI 4.8–31.5) vs 51.8 % (95 % CI 31,9–68.5), p = 0.004; 7.7 % (95 % CI 1.3–21.7) vs 33.3 (95 % CI 16.8–50.9), p = 0.026; 23.4 % (95 % CI 9.5-41.0) vs 58.6 % (95 % CI 33.8–76.8), p = 0.022; 3.8 % (95 % CI 0.3–16.4) vs 25.9 % (95 % CI 11.5–43.1), p = 0.0232, respectively. GVHD-related mortality was higher in the historical control group than in the PTC group (3.8 % vs 18.5 %, p = 0.192). Thus, PTC-based GVHD prophylaxis was shown to be more effective in managing acute and chronic GVHD compared to antithymocyte globulin, with better overall, relapse-free and GVHD-free relapse-free survival rates and low transplant-related mortality.

Relapse of acute myeloid leukemia (AML) after allogeneic hematopoietic stem cell transplantation (allo-HSCT) remains one of the main causes of reduced long-term survival. Modern methods for predicting the risk of AML relapse after allo-HSCT take into account the data on the pre-transplant level of minimal residual disease (MRD) determined by flow cytometry and molecular biological studies of recurrent genetic abnormalities, which are currently widespread in clinical practice. Recent studies of the expression of genes characteristic of leukemic stem cells (LSCs) have shown prognostic significance for children with AML in relation to treatment response and the risk of relapse. The study of LSC persistence in order to predict the risk of recurrence after allo-HSCT in children with AML in addition to standard MRD detection methods may be of great importance. The aim of the work was to evaluate the impact of MRD status, both using classic methods and taking into account the genes characteristic of LSC, on the results of allo-HSCT in children with AML. The study was approved by the Independent Ethics Committee and the Scientific Council of the I.P. Pavlov First Saint Petersburg State Medical University of Ministry of Healthcare of the Russian Federation. To assess MRD using standard diagnostic methods, we analyzed the data of 95 children with AML in their 1 st –2 nd remission (cohort 1). MRD status was negative in 67 (70.6 %) patients; in 28 (29.4 %) children, MRD status was positive according to molecular genetic studies and / or immunophenotyping results. For pre-transplant evaluation of the expression of genes characteristic of LSC, we investigated bone marrow samples of 50 patients (cohort 2) using real-time polymerase chain reaction. The DNMT3B , GPR56 , CD34 , SOCS2 , SPINK2 , FAM30A , and ABL genes were studied by real-time polymerase chain reaction, followed by calculation of the pLSC6 value using the formula: DNMT3b × 0.189 + GPR56 × 0.054 + CD34 × 0.0171 + SOCS2 × 0.141 + SPINK2 × 0.109 + FAM30A × 0.0516. At the time of allo-HSCT, 37 (74 %) children with AML were in their 1 st or 2 nd remission of the disease, 13 (26 %) were out of the 1 st –2 nd remission. With a median follow-up of 5 years in the group of patients with a positive MRD status, determined by standard methods (cohort 1), overall survival (OS) was 67.9 % vs 73.1 % for patients with a negative MRD status (p = 0.83). The cumulative incidence of relapse was 50 % and 22 %, respectively; p = 0.012. When assessing the level of expression of genes characteristic of LSC (cohort 2), a pLSC6 level was above the median in 18/37 (49 %) patients. The results of linear regression showed that the pre-transplant level of expression of genes characteristic of LSC was not associated with the number of blasts/MRD (odds ratio 1.002; 95 % confidence interval 0.979–1.025). One-year OS rates did not differ significantly in children in the 1st–2nd remission of AML, depending on pLSC6 level: 84.2% in patients with low pLSC6 and 72.2 % – with high pLSC6 (p = 0.4), event-free survival in the corresponding groups – 68.4 % and 61.1 %, respectively (p = 0.34). The cumulative incidence of early relapse after allo-HSCT in the group of AML patients with a high pLSC6 score was significantly higher than in children with a low pLSC6 score before allo-HSCT (22 % and 0 %, respectively; p = 0.03). MRD does not have a statistically significant effect on OS. However, MRD positivity before allo-HSCT increases cumulative incidence of relapse. The level of expression of genes characteristic of LSC, determined before allo-HSCT, showed a prognostic significance in relation to the development of early AML relapse after allo-HSCT.

Juvenile myelomonocytic leukemia (JMML) is a rare and aggressive myeloproliferative/myelodysplastic neoplasm of early childhood characterized by activation of the Ras signaling pathway. Allogeneic hematopoietic stem cell transplantation (alloHSCT) is the only proven curative treatment for JMML. However, the 5-year overall survival is about 52–64%. In this work, we analyzed 4 clinical cases of patients with relapses of JMML with loss of heterozygosity in HLA (LoH) after allo-HSCT. The patients' parents gave their consent to the use of their children's data, including photographs, for research purposes and in publications. Two patients received a second allo-HSCT from an alternative donor, two patients – from the same donor. A positive result in the form of a durable remission was observed in one patient who underwent a second allo-HSCT from an alternative donor and restored HLA genetic heterozygosity. At the same time, immunotherapy with infusions of donor lymphocytes led to the development of graft-versus-host disease without potentiating the antileukemic effect. Thus, a second allo-HSCT from an alternative donor for the treatment of relapsed JMML with HLA LoH is necessary to restore the “graft-versus-JMML” response. The study was approved by the Independent Ethics Committee and the Scientific Council of the I.P. Pavlov First Saint Petersburg State Medical University of Ministry of Healthcare of the Russian Federation.

The loss of a patient-specific HLA haplotype on the surface of the blast cell population is one of the ways a tumor can evade the immune surveillance of donor cells. This phenomenon is observed in approximately 30 % of relapses in patients with hematologic malignancies who underwent partially mismatched allogeneic hematopoietic stem cell transplantation (HSCT). In this study, for the first time, a large cohort of pediatric patients (n = 80) with relapsed acute myeloid (AML) or acute lymphoblastic (ALL) leukemia after allogeneic HSCT was analyzed with the help of the STR method (highlypolymorphic microsatellite marker analysis) using 6 HLA haplotype markers. The study was approved by the Independent Ethics Committee and the Scientific Council of the I. P. Pavlov First Saint Petersburg State Medical University of Ministry of Healthcare of the Russian Federation. Loss of heterozygosity (LOH) was observed in 18 / 80 (22 %) relapsed patients with various types of acute leukemia: out of these, 8 / 44 (18 %) patients had B-cell ALL, 4 / 10 (40 %) patients – T-cell ALL and 6 / 25 (24 %) patients – AML. All relapses with LOH were observed in patients who had undergone haploidentical HSCT, and were found to occur later than relapses without loss of the HLA haplotype (median time to relapse: 8.8 months vs 6.2 months, p = 0.043). In the patients treated with haploidentical HSCT (n = 61), we assessed factors increasing the risk of LOH at relapse. The number of previous therapy lines in the patients with AML (n = 17) and acute or chronic graft-versus-host disease in the patients with ALL (n = 44) were associated with an increasedrisk of genetic loss of the HLA haplotype (p = 0.008 and p = 0.015 respectively). A relapse following the second allogeneic HSCT was associated with LOH in 4 / 5 (80 %) patients, p = 0.008. The prognosis of the patients with LOH was extremely poor. At a median follow-up of 6 months, the overall survival from relapse was 22 % in the LOH group and 37 % in the non-LOH group. The median overall survival was 4.5 months (95 % confidence interval 3–NA) and 10.3 months (95 % confidence interval 5.7–16.1) respectively, p = 0.063. Among the patients with LOH, the best survival rates were observed in those who had undergone a repeat allogeneic HSCT from a different donor. Thus, the analysis of LOH is an important tool for determining the prognosis and further treatment in pediatric patients with acute leukemias. We strongly recommend that this diagnostic test should be included into standard testing of patients after partially-mismatched allogeneic HSCT.

Relevance . Allogeneic hematopoietic stem cell transplantation (allo-HSCT) makes it possible to treat severe malignant and non-malignant hematopoietic disorders system. Pulmonary complications (PC) occur in 40–60 % of patients after allo-HSCT. However to date, the effect of HSCT on functional and morphological pulmonary changes in recipients remains insufficiently studied. The objective of current study was to evaluate risk factors affecting long-term survival in children and adolescents after allo-HSCT. Methods and materials . The current study was both retrospective and prospective. The analysis included 362 patients with acute lymphoblastic leukemia (ALL) and acute myeloid leukemia (AML), aged 5 months to 18 years, who received allo-HSCT at Raisa Gorbacheva Memorial Research Institute for Pediatric Oncology, Hematology and Transplantation in 2000–2018. All the patients underwent chest computed tomography (CT). When detecting CT changes, we performed fibrobronchoscopy (FBS) with microbiological examination of bronchoalveolar lavage (BAL). Results . PC were diagnosed in 124 patients (64 %) who received allo-HSCT in 2014–2018. Decrease of overall survival (OS) is associated with PC development during the first year after allo-HSCT(р<0,001).The development of early PC in remission of the underlying disease significantly affected OS (p=0.001).The probability of PC development is 2.26 times higher in patients older than 9 years (p=0.006). When comparing the intensity of conditioning regimens (MACvsRIC) in remission of the underlying disease, we did not get significant differences in the incidence of PC (p>0.05). Graft source, donor type, HLA-compatibility, recipient gender did not affect the incidence of PC (p>0.05). When using graft-versus-host disease (GVHD) prophylaxis (ptCYvsATG), the 5-year OS in patients without PC was 78.8 % and 62.8 %respectively. The 5-year OS in patients with PC was 51.8 % and 42.4 % respectively (р=0.007). Decrease of OS in patients with PC is associated with chGVHD(58.3 %,) (р=0.03). Conclusion . Pulmonary complications (infectious and non-infectious) in allo-HSCT recipients are more likely to occur in the first year after transplantation. Among bacterial pathogens, the predominance of Gr(-) flora remains. The incidence of pulmonary complications was significantly lower when using ptCY as a prevention of GVHD.

Профилактические инфузии донорских лимфоцитов используют у пациентов с высоким риском развития рецидива заболевания после алло-ТГСК. Данные по безопасности раннего введения ИДЛ у детей крайне ограничены. В работе отражены частота клинически значимой реакции «трансплантат против хозяина» (РТПХ) и ее связь с общей и безрецидивной выживаемостью. Проанализированы 37 детей с острыми лейкозами и ЮММЛ, получивших профилактические ИДЛ в течение первых 6 месяцев после алло-ТГСК. Развитие острой/хронической РТПХ средней степени выявлено у 7 из 37 детей (19%), не отмечено тяжелых форм РТПХ. Наиболее часто диагностировали кожную форму хронической РТПХ в сочетании с поражением печени. Случаи летальности, связанные с осложнениями после ИДЛ, не были зарегистрированы. Напротив, индукция острой/хронической РТПХ улучшала показатели безрецидивной выживаемости и не влияла на общую выживаемость, p=0,04 и p=0,3 соответственно. Prophylactic donor lymphocytes infusion (DLI) is used in patients with a high risk of relapse after allo-HSCT. The data about safety of early start DLI in children are extremely limited. This study demonstrates the incidence of clinically significant graft versus host disease (GVHD) and correlation with overall and disease-free survival. We analyzed 37 children with acute leukemia and JMML, who had received prophylactic DLI within the first 6 months after HSCT. Moderate acute/chronic GVHD was diagnosed in 7/37 children (19%), nobody developed severe GVHD. The most children had chronic GVHD with involvement of skin and liver. There were no cases GVHD-related mortality. The induction of acute/chronic GVHD improved the relapse-free survival and did not influence on overall survival, p=0.04 and p=0.3, respectively.

Randomized multicenter trials in the area of hematopoietic stem cell transplantation (HSCT) face considerable challenges, therefore, their amount is relatively small. Most clinical guidelines are based on the data of multicenter registry studies or well-controlled prospective single-center non-randomized studies. To determine the criteria of a well-controlled single-center trial the results of which can be confi rmed by a multicenter analysis, the total of 44 groups of patients from 22 cooperative studies in collaboration with EBMT were analyzed. The results of these studies were compared with single-center data and the results of the planned studies of RM Gorbacheva Scientifi c Research Institute of Pediatric Oncology, Hematology and Transplantation. In 43 % of cases signifi cant diff erences were observed. The probability of diff erences did not decrease with an increasing number of patients in the single-center groups, but became higher (odds ratio 1.037; 95% confi dence interval 1.001-1.074; p = 0.046), which highlights the diff erences in methods of single- and multicenter trials. While analyzing the reasons for signifi cant diff erences the following necessary criteria for high-quali ty single-center trials in the area of HSCT were formulated: 1) conditioning regimens and graft-versus-host disease prophylaxis (if they are not subject of the study) need to be consistent with the most frequently used practices; 2) groups of patients should be status-homogeneous; 3) the trial must not include patients treated more than 5 years before the analysis; 4) patients should receive current antitumor therapy at pre- and post-transplantation stages; 5) each compared group should include more than 30-40 patients

Проведение рандомизированных многоцентровых исследований в области трансплантации гемопоэтических стволовых клеток (ТГСК) представляет значительные трудности, поэтому доля таких исследований невелика. Большинство клинических рекомендаций основывается на данных популяционных многоцентровых исследований регистров или хорошо контролируемых проспективных одноцентровых нерандомизированных исследований. С целью определить критерии хорошо контролируемого одноцентрового исследования, результаты которого могут быть подтверждены в многоцентровом анализе, проанализировано 44 группы пациентов из 22 совместных с группой EBMT исследований. Проведено сравнение результатов этих исследований с одноцентровыми данными и спланированными исследованиями НИИ ДОГиТ им. Р.М. Горбачевой. Выявлено, что статистически значимые различия наблюдались в 43 % случаев, при этом вероятность расхождения результатов при повышении числа пациентов в одноцентровых группах не уменьшалась, а увеличивалась (отношение шансов 1,037; 95%-й доверительный интервал 1,001–1,074; p = 0,046), что свидетельствует о различиях в методологии одноцентровых и многоцентровых исследований. При анализе причин статистически значимых результатов сформулированы следующие необходимые критерии высококачественных одноцентровых исследований в области ТГСК: 1) режимы кондиционирования и профилактики реакции «трансплантат против хозяина» (если они не являются предметом исследования) должны соответствовать наиболее часто используемым в практике; 2) группы пациентов должны быть однородными по своему статусу; 3) в исследование не должны включаться пациенты, получавшие лечение более чем за 5 лет до анализа; 4) пациенты должны получать современную противоопухолевую терапию на до- и посттрансплантационном этапах; 5) каждая сравниваемая группа должна включать более 30–40 пациентов.