BACKGROUND:Quantitative measurement of minimal residual disease (MRD) is the "gold standard" for estimating the response to therapy in childhood B-cell precursor acute lymphoblastic leukemia (BCP-ALL). Nevertheless, the speed of the MRD response differs for different cytogenetic subgroups. Here we present results of MRD measurement in children with BCP-ALL, in terms of genetic subgroups with relation to clinically defined risk groups. METHODS:A total of 485 children with non-high-risk BCP-ALL with available cytogenetic data and MRD studied at the end-of-induction (EOI) by multicolor flow cytometry (MFC) were included. All patients were treated with standard-risk (SR) of intermediate-risk (ImR) regimens of "ALL-MB 2008" reduced-intensity protocol. RESULTS AND DISCUSSION:Among all study group patients, 203 were found to have low-risk cytogenetics (ETV6::RUNX1 or high hyperdiploidy), while remaining 282 children were classified in intermediate cytogenetic risk group. For the patients with favorable and intermediate risk cytogenetics, the most significant thresholds for MFC-MRD values were different: 0.03% and 0.04% respectively. Nevertheless, the most meaningful thresholds were different for clinically defined SR and ImR groups. For the SR group, irrespective to presence/absence of favorable genetic lesions, MFC-MRD threshold of 0.1% was the most clinically valuable, although for ImR group the most informative thresholds were different in patients from low-(0.03%) and intermediate (0.01%) cytogenetic risk groups. CONCLUSION:Our data show that combining clinical risk factors with MFC-MRD measurement is the most useful tool for risk group stratification of children with BCP-ALL in the reduced-intensity protocols. However, this algorithm can be supplemented with cytogenetic data for part of the ImR group.

Translocation t(12;21)(p13;q22)/ETV6::RUNX1 is among the most common genetic aberrations in pediatric B-cell precursor acute lymphoblastic leukekian (BCP-ALL). This translocation is often combined with ETV6 and/or RUNX1 copy number variations. Fluorescence in situ hybridization (FISH) technique, which is widely used to reveal the presence of t(12;21)(p13;q22), also allows the detection of these additional genetic aberrations (FISH patterns). The aim of this study was to provide detailed characteristics of FISH patterns in patients with BCP-ALL and the t(12;21)(p13;q22)/ETV6::RUNX1 translocation. In our study we enrolled 241 patients with t(12;21)-positive ALL who had undergone testing with a dual-color double-fusion FISH assay between 2008 and 2023. This study was approved by the Independent Ethics Committee and the Academic Council of the Research Institute of Medical Cell Technologies (Ekaterinburg). A single FISH pattern (monoclonal cases) was identified in 200 patients (83.0%), 2 or more patterns (polyclonal cases) were detected in 41 (17.0%) patients. The majority of polyclonal cases (n = 39; 95.1%) exhibited 2 patterns. The most common secondary genetic alteration was ETV6 deletion (n = 105; 43.5%). Less common aberrations included an additional copy of RUNX1 (n = 97; 40.2%), a combination of ETV6 deletion and an additional copy of RUNX1 (n = 27; 11.2%), and an additional copy of ETV6 (n = 5; 2.0%). The number of the patients with one FISH pattern that did not contain any additional genetic aberrations as a result of a reciprocal translocation (2F1G1R) was relatively small (n = 35; 17.5%). We identified 5 prognostically unfavorable FISH patterns associated with a high risk of relapse. These included cases with simultaneous presence of ETV6 and RUNX1 additional copies (pattern 2F2G2R), isolated additional copies of RUNX1 (pattern 2F2R-3F2R) or ETV6 (pattern 1F1G2R-2F2G4R), a partial deletion of ETV6 (pattern 2F1Gdim1R) and a non-reciprocal translocation of t(12;21) (pattern 1F1R-1F1G1R). Grouping these unfavorable prognostic FISH patterns together made it possible to predict 6 (46%) out of 13 relapses that occurred in the patients during the study period. It is important to highlight that the number of the patients with unfavorable FISH patterns and initial leukocytosis of > 30 × 109 leukocytes/L did not differ significantly from the rest of the group. Another important observation was that the patients with prognostically unfavorable FISH patterns responded well to induction therapy, as assessed both by cytological examination of blood and bone marrow smears on days 8, 15, and 36 of therapy and by MRD response at the end of induction therapy according to the ALL-MB 2015 protocol. A comparison of FISH patterns detected at initial diagnosis and at relapse showed that only 6 (50%) out of 12 cases who had undergone FISH testing at both time points remained stable. In conclusion, BCP-ALL with the translocation t(12;21)(p13;q22)/ETV6::RUNX1 was characterized by a vast variety of secondary genetic aberrations detected by FISH, the most prevalent of which was ETV6 deletion. A group of unfavorable FISH patterns identified in our study warrants further investigation in a larger cohort of ALL patients for their possible re-stratification so that they could receive more intensive treatment.

This report presents the results of the assessment of MRD response by multicolor flow cytometry (MFC) with regard to the randomized use of pegylated asparaginase (PEG). In this study, PEG was randomly administered at a dose of 1000 U/m2 on day 3 of induction therapy in children with B-lineage ALL. Methods. Conventional induction therapy consisted of dexamethasone, vincristine, and daunorubicin. MRD data was available in 502 patients who were randomized at the start of induction therapy, standard-risk (SR) patients into three (conventional induction without PEG, induction with additional PEG and with PEG but without daunorubicin) and intermediate-risk (ImR) patients into two groups (with additional PEG and without PEG). Results. The single administration of PEG resulted in a significantly higher proportion of rapid responders, in SR patients even when no anthracyclines were used for induction. In the SR group, the event-free survival of the MFC-MRD fast responders was similar in the PEG− and PEG+ arms (92.0 ± 3.1% vs. 96.2 ± 1.5%, respectively), and the same unfavorable trend was observed for MFC-MRD slow responders (57.5 ± 12.3% vs. 66.7 ± 15.7%, respectively). Results were similar in ImR patients: (94.3 ± 3.2% vs. 95.1 ± 2.4%, for fast responders and 63.3 ± 7.6% vs. 78.1 ± 7.9%, for slow responders in PEG− and PEG+ arms, respectively). However, there is a large difference between the proportion of MFC-MRD slow responders in the PEG− and PEG+ groups (18.3% vs. 5.2% for the SR group and 44.2% vs. 25.0% for the ImR group). Conclusions. Therefore, early use of PEG-ASP not only leads to an accelerated reduction of blasts, but also to an excellent outcome in a significantly larger proportion of patients in both risk groups.

Sequential monitoring of minimal residual disease (MRD) by molecular techniques or multicolor flow cytometry (MFC) has emerged over the past two decades as the primary tool to optimize treatment in pediatric B‐cell precursor acute lymphoblastic leukemia (BCP‐ALL). The aim of our study was to compare the prognostic power of repeated MFC–MRD measurement with single‐point MRD assessment in children with BCP‐ALL treated with the reduced‐intensity protocol ALL‐MB 2008. Data from consecutive MFC–MRD at day 15 and day 36 (end of induction, EOI) were available for 507 children with Philadelphia‐negative BCP‐ALL. They were stratified into standard risk (SR, n = 265), intermediate risk (ImR, n = 211), and high risk (HR, n = 31) according to the initial clinical characteristics defined in the ALL‐MB 2008 protocol. Quantitative (relative to quantitative thresholds) and kinetic (logarithmic reduction) assessments of MFC–MRD at both time points effectively separated patients into three groups with different risk of recurrence. On the other hand, starting with low (for the SR group) and moderate (for the ImR group) induction therapy, a single MFC–MRD measurement at EOI proved sufficient to unequivocally identify patients in whom this therapy is highly effective and distinguish them from those who cannot be successfully treated with such therapy. Therefore, initiating treatment with low or moderate treatment from the start, together with careful consideration of initial clinical risk factors and just one EOI–MFC–MRD measurement is simple, inexpensive, and entirely sufficient for treatment optimization. Furthermore, for a large proportion of patients, this approach allows better adjustment, in particular also reduction of therapy intensity than sequential MRD measurements.

The aim of this study was to present the diagnostic and outcome characteristics of infants with germline status of KMT2A gene (KMT2A‐g) B‐cell precursor acute lymphoblastic leukemia (BCP‐ALL) treated consistently according to the MLL‐Baby protocol, a moderate‐intensity protocol. Of the 139 patients enrolled in the MLL‐Baby study, 100 (71.9%) carried different types of rearranged KMT2A (KMT2A‐r), while the remaining 39 infants (28.1%) had KMT2A‐g. KMT2A‐g patients were generally older (77% older than 6 months), less likely to have a very high white blood cell count (greater than 100 × 109/L), less likely to be central nervous system (CNS)‐positive, and more likely to be CD10‐positive. The 6‐year event‐free survival and overall survival rates for all 39 patients were 0.74 (standard error [SE] 0.07) and 0.80 (SE 0.07), respectively. Relapse was the most common adverse event (n = 5), with a cumulative incidence of relapse (CIR) of 0.13 (SE 0.06), while the incidence of a second malignancy (n = 1) and death in remission (n = 3) was 0.03 (SE 0.04) and 0.08 (SE 0.04), respectively. None of the initial parameters, including genetics and the presence of recently described fusions of NUTM1 and PAX5 genes, was able to distinguish patients with different outcomes. Only rapidity of response, measured as minimal residual disease (MRD) by flow cytometry, showed a statistically significant impact. Moderate‐intensity therapy, as used in the MLL‐Baby protocol in infants with KMT2A‐g BCP‐ALL, yields results comparable to other infant studies. Patients with a slow multicolor flow cytometry (MFC)‐MRD response should be subjected to advanced therapies, such as targeted or immunotherapies.

We compared the efficacy and safety of eltrombopag (ELTR) combined with immunosuppressive therapy (IST) and IST alone in treatment-naive children with severe (SAA) and very severe (vSAA) aplastic anemia. Ninety-eight pediatric patients were randomized to receive horse antithymocyte globulin (hATG) and cyclosporin A (CsA) with (n = 49) or without (n = 49) ELTR. The primary endpoint was the overall response rate (ORR) at 4 months. After 4 months, nonresponders were crossed over to the alternative group. In all patients, the ORR in ELTR + IST and IST groups was similar (65% vs 53%; P = .218); however, the complete response (CR) rate was significantly higher in the ELTR + IST group (31% vs 12%; P = .027). In severity subgroups, the ORR was 89% vs 57% (P = .028) in favor of IST + ELTR in SAA, but it did not differ in patients with vSAA (52% vs 50%; P = .902). At 6 months after the crossover, 61% of initial ELTR(-) patients achieved a response compared with 17% of initial ELTR(+) patients (P = .016). No significant difference in ELTR + IST and IST groups was observed in the 3-year overall survival (OS) (89% vs 91%; P = .673) or the 3-year event-free survival (EFS) (53% vs 41%; P = .326). There was no unexpected toxicity related to ELTR. Adding ELTR to standard IST was well tolerated and increased the CR rate. The greatest benefit from ELTR combined with IST was observed in patients with SAA but not in those with vSAA. The second course of IST resulted in a high ORR in initial ELTR(-) patients who added ELTR and had limited efficacy among patients who received ELTR upfront. This trial was registered at Clinicaltrials.gov as #NCT03413306.

The achievement of remission at the end of induction (EOI) chemotherapy in patients with acute lymphoblastic leukemia (ALL) is the key parameter of treatment effectiveness evaluation. The aim of the study – defining complete remission by multicolor flow cytometry (MFC) and bone marrow (BM) cytomorphology (CM) at the EOI chemotherapy in children with B-lineage ALL. The study was approved by the Independent Ethics Committee and the Scientific Council of the Dmitry Rogachev National Medical Research Center of Pediatric Hematology, Oncology and Immunology. The study included patients of “ALL-MB 2008” and “ALL-MB 2015” trials for whom minimal residual disease (MRD) was evaluated by MFC at the EOI simultaneously with CM BM investigation. Less than 5% blasts in BM and MRD < 1% were established as the remission achievement criteria for CM and MFC respectively. The study group included 1498 children aged from 1 to 18 years (median age was 4 years and 11 months) with B-cell precursor ALL. The overall concordance of MFC and CM was found to be 96.1% (1440 of 1498 patients). In 36 (2.4%) children with MRD ≥ 1%, M1 BM status was observed. In contrast, in 22 (1.5%) patients with M2/M3 BM status by CM, MRD value was below 1%. Treatment outcome was analyzed in 522 patients of “ALL-MB 2008” trial. Children with M2/M3 BM, as well as with MRD ≥ 1% demonstrated dramatically inferior outcome, in comparison to those who achieved remission. The presence of at least one of the mentioned criteria (M2/M3 status by CM or MRD ≥ 1% by MFC) defined a group of 23 (4.4%) patients with very low event-free survival (34.9%, standard error 11.0%) and very high cumulative incidence of relapse (56.4%, standard error 12.0%). For the evaluation of remission achievement, MFC and CM should be applied simultaneously at the EOI. High leukemic burden found by any of these methods is the clear definition of induction failure. MRD detection at the EOI should be implemented in any modern treatment protocol as an obligatory stage of treatment response monitoring and final risk group stratification. Considering the crucial importance of the MRD detection results, this study must be performed only in the reference laboratories of the study groups.

Serious side effects occur during therapy for childhood acute lymphoblastic leukemia (ALL), and survivors can experience long-term consequences. This study aimed at identifying patients who can be successfully treated with low treatment intensity combining clinical parameters and minimal residual disease (MRD) measurements. The study was approved by the Independent Ethics Committee and the Scientific Council of the Dmitry Rogachev National Medical Research Center of Pediatric Hematology, Oncology and Immunology. ALL-MB studies used reduced-intensity therapy from the beginning, for standard risk (SR) patients no cyclophosphamide, a very low daunorubicin dose, no high dose of methotrexate, no cranial irradiation. In the ALL-MB 2008 study, 1702 children (49.1 % of all patients) were classified as SR due to favorable initial characteristics. These included 295 patients treated in institutions who took part in a pilot study on MRD measurement using flow cytometry on day 15 and/or at the end of induction (EOI). The most suitable time point for MRD measurement was EOI with threshold 0.1% in 90.5 % of the patients with excellent results: event-free survival of 95 % and overall survival of 97 %, that identified the large proportion of patients (more than 40 % of all ALL patients). The outcome of children with slower MRD response was significantly worse. Initial SR characteristics plus one single MRD measurement at EOI identify more than 40 % of all children with ALL who can be successfully treated with low-intensity regimens as used in the MB protocols.

Aim The aim of the study was to evaluate the incidence and prognostic impact of central nervous system (CNS) involvement in infants with B-cell precursor acute lymphoblastic leukemia (BCP-ALL), as well as its relation with minimal residual disease (MRD) data. Methods A total of 139 consecutive infants with BCP-ALL from the MLL-Baby trial were studied. Cerebrospinal fluid (CSF) samples were investigated by microscopy of cytospin slides. MRD was evaluated according to the protocol schedule by flow cytometry and PCR for fusion gene transcripts (FGT). Results Involvement of the CNS at any level was found in 50 infants (36.0%). The incidence of CNS involvement was higher in patients with KMT2A gene rearrangements (44.0% for KMT2A-r vs. 15.4% for KMT2A-g, p = .003). The outcome of CNS-positive infants was significantly worse than that of CNS-negative infants, although this prognostic impact was limited to the KMT2A-r group (event-free survival 0.21 for CNS-positive vs. 0.48 for CNS-negative infants, p = .044). CNS-positive infants could not be treated successfully by conventional chemotherapy alone, irrespective of the rapidity of MRD response. In contrast, the combination of initial CNS negativity and FGT-MRD negativity identified a group comprising up to one-third of infants with KMT2A-r ALL who can be treated with chemotherapy and achieve very good outcomes (disease-free survival above 95%), and remaining patients should be allocated to receive other types of treatment. Conclusion We can conclude that this combination of initial CNS involvement and MRD data can significantly improve risk-group allocation in future clinical trials enrolling infants with ALL.

The excellent results of posttransplant cyclophosphamide in decreasing graft-versus-host disease (GVHD) after haploidentical (HI) allogeneic transplant have challenged current donor selection algorithms.We compared outcomes after matched sibling (MSD) versus alternative donor transplant using identical graft-versus-host disease (GVHD) prophylaxis including posttransplant cyclophosphamide (PTCy. Endpoints included engraftment, time outside of the hospital in the first 100 days after transplant, overall survival (OS), non-relapse mortality (NRM) and percentage of patients disease-free and off immunosuppression (DFOI) at one year and at the last follow-up.There were significant differences at baseline between matched donor versus HI donor transplants with higher disease-risk index (DRI), more female-to-male donor recipient pairs and a higher percentage of Black patients in the HI group. Engraftment and time out of the hospital favored MSD and matched unrelated donor transplants. Multivariate analysis showed that high DRI and Black race were associated with decreased survival and Black race was associated with a higher NRM.With the use of PTCy, our results support current donor selection algorithms. The finding of decreased survival and increased NRM in Black patients requires confirmation in a larger number of patients as well as the development of mitigation strategies.

The paper presents the results of a multicenter randomized study of two-dose COLI-ASP regimens in therapy of consolidation of standard risk-group (SRG) children and adolescents with acute lymphoblastic leukemia (ALL) treated by the ALL-MB-2002 protocol. The principal aim of the study was to elucidate whether the dose of COLI-ASP might be reduced without losing the efficiency of therapy. The analysis covered primary ALL patients notified at 36 clinics of Russia and Belarus, enrolled for the study in the period of May 1, 2002, to October 10, 2006. Out of 819 patients to be examined, 414 received COLI-ASP in a dose of 10,000 U/m2 (a control group), and 405 children took it in a dose of 5,000 U/m2 (a study group). No statistically significant differences were found between the patients in gender, age, baseline leukocytosis, and spleen size. The study showed no statistically and clinically significant differences in event-free, overall, and relapse-free survival (EFS, OS, and RFS, respectively) and relapse rates with the use of two-dose COLI-ASP regimens. However, in the control group, the death rate in remission was twice greater than that in the study group (p = 0.02). Detailed analysis of the outcomes of therapy in some subgroups revealed no differences between the control and study groups. The Cox multiple regression analysis has indicated that the factors influencing EFS and RFS are the baseline sizes of the spleen, baseline leukocytosis, age, and a response to treatment in the period of induction, rather than the dose of E. coli asparaginase. The authors have also found that among the SRG patients, there is a subgroup of patients without risk factors, in whom the reduction in the COLI-ASP dose may substantially increase survival rates, by lowering toxicity and mortality in remission.

Measurement of minimal residual disease (MRD) with multicolor flow cytometry (MFC) has become an important tool in childhood acute lymphoblastic leukemia (ALL), mainly to identify rapid responders and reduce their therapy intensity. Protocols of the Moscow–Berlin (MB) group use a comparatively low (for standard risk; SR) or moderate (for intermediate risk; ImR) treatment intensity from the onset, based on initial patient characteristics. Recently, we reported that 90

Проанализирована значимость прогностических факторов эффективности терапии у детей с острым лимфобластным лейкозом (ОЛЛ), получающих терапию по протоколу ALL-MB-2002, в зависимости от группы риска. В исследование были включены 1544 первичных больных ОЛЛ в возрасте от 1 года до 18 лет, получавших лечение в 36 клиниках России и Беларуси в период с 15 апреля 2002 г. до 1 января 2008 г. Из 1544 больных, включенных в анализ, пациенты группы стандартного риска (SRG) составили 69,2 %, промежуточного риска (ImRG) — 24,5 % и 6,3 % пациентов были отнесены к группе высокого риска. Анализ, проведенный у пациентов SRG, продемонстрировал резкие различия в выживаемости между отдельными подгруппами больных. Выявлены достоверные различия в показателях выживаемости пациентов в зависимости от возраста (старше и младше 10 лет), инициального лейкоцитоза (более и менее 30 × 10 9 /л), инициального пальпаторного увеличения селезенки (более и менее 4 см из-под края реберной дуги) и параметров раннего ответа на терапию (8-й и 15-й день). При ретроспективном определении больных, относящихся к SRG, с использованием новых критериев (инициальный лейкоцитоз <30 × 10 9 /л; селезенка < 4 см), прогностическая значимость раннего ответа на терапию нивелировалась. Среди пациентов ImRG не обнаружено никаких достоверных различий в показателях бессобытийной, общей и безрецидивной выживаемости и риске развития изолированных нейрорецидивов в зависимости от инициального иммунофенотипа бластных клеток (Т-ОЛЛ/не-Т-ОЛЛ). Шестилетний кумулятивный риск развития изолированных нейрорецидивов не различался у пациентов с Т- и не-Т-ОЛЛ, однако был выше у больных с инициальным лейкоцитозом ≥ 100 × 10 9 /л независимо от иммунофенотипа. Наихудшие показатели выживаемости отмечены у пациентов с не-Т-ОЛЛ и количеством лейкоцитов ≥ 100 × 10 9 /л — бессобытийная выживаемость в этой подгруппе составила всего 58 ± 7 %. При проведении многофакторного анализа выявлено, что для пациентов с Т-ОЛЛ независимое прогностическое влияние на выживаемость оказывает только величина инициального лейкоцитоза (р = 0,0333), тогда как для больных не-Т-ОЛЛ независимое значение имеют возраст (р = 0,0063), инициальный лейкоцитоз (р = 0,0066) и наличие поражения центральной нервной системы (р = 0,0112).Перенести в английский вариант Prognostic significance of different risk factors in children with acute lymphoblastic leukemia (ALL) treating according to ALL-MB 2002 protocol depending on risk group is analyzed. 1544 primary patients aged from 1 to 18 years, treating in 36 clinics of Russia and Belarus from April, 15 th , 2002 to January, 1th, 2008, was included in the study. From 1544 patients included, 69.2% were standard risk group (SRG), 24.5 % — intermediate risk group (ImRG) and 6.3% — high risk group. The expressed differences in survival rate between certain patient’s subgroups were revealed. Significant survival differences according to age (older and younger 10 years), initial leukocyte count (more and less than 30 × 10 9 /l), spleen size (more and less 4 cm below a costal arch at a palpation) and early therapy response (8th and 15th days of induction) are revealed. At retrospective definition of SRG patients with use of new criteria (initial leukocytosis < 30 × 10 9 /l and spleen size <4 cm), prognostic significance of therapy response was leveled in this subgroup of patients. Among ImRG patients any significant differences in EFS, OS, RFS and cumulative risk of isolated CNS (CIR IN ) relapse according to blast cells immunophenotype (T-ALL/non-T-ALL) were not shown. 6-years CIRIN was not different between patients with T-ALL and non-T-ALL, however was high in patients with initial leukocyte count ≥ 100 × 10 9 /l irrespective to immunophenotype. The worst survival appeared in patients with non-T-ALL and leukocyte count ≥100 × 10 9 /l — EFS in this subgroup was only 58±7%. Only initial leukocytosis had prognostic significance for patients with T-ALL (р=0.0333), whereas age (р = 0.0063), initial leukocytosis (р = 0.0066) and CNS involvement (р = 0.0112) as independent prognostic factors for patients with non-T-ALL in multifactorial analysis was revealed.

This study aimed to evaluate the concordance between minimal residual disease (MRD) results obtained by multicolour flow cytometry (MFC) and polymerase chain reaction for fusion gene transcripts (FGTs) in infants with acute lymphoblastic leukaemia (ALL) associated with rearrangement of the KMT2A gene (KMT2A-r). A total of 942 bone marrow (BM) samples from 123 infants were studied for MFC-MRD and FGT-MRD. In total, 383 samples (40.7%) were concordantly MRD-negative. MRD was detected by the two methods in 441 cases (46.8%); 99 samples (10.5%) were only FGT-MRD-positive and 19 (2.0%) were only MFC-MRD-positive. A final concordance rate of 87.4% was established. Most discordance occurred if residual leukaemia was present at levels close to the sensitivity limits. Neither the type of KMT2A fusion nor a new type of treatment hampering MFC methodology had an influence on the concordance rate. The prognostic value of MFC-MRD and FGT-MRD differed. MFC-MRD was able to identify a rapid response at early time-points, whereas FGT-MRD was a reliable relapse predictor at later treatment stages. Additionally, the most precise risk definition was obtained when combining the two methods. Because of the high comparability in results, these two rather simple and inexpensive approaches could be good options of high clinical value.

The purpose of this work was evaluation of prognostic significance of 11q23/KMT2A rearrangements in infants (aged under 365 days) with B-cell precursor acute lymphoblastic leukemia (ALL) enrolled in Russian-Belarus multicenter trial MLLBaby. This study is supported by the Independent Ethics Committee and approved by the Academic Council of the Research Institute of Medical Cell Technologies (Ekaterinburg). Various 11q23/KMT2A rearrangements were revealed in 100 (72%) of 139 patients. Event-free survival (EFS) in the intermediate risk group of MLL-Baby trial was 35.1% (standard error (SE) 6.9%), in the high risk group – 38.3% (SE 7.1%) (p = 0.941). The most unfavorable prognosis had infants with translocation t(9;11)/KMT2A-MLLT3: EFS 18.8% (SE 9.8%), cumulative incidence of relapse (CIR) 75.0% (SE 9.7%). Intermediate results were obtained in patients with translocations t(4;11)/KMT2A-AFF1 and t(11;19)/KMT2A-MLLT1: EFS 36.9% (SE 7,2%) and 32,7% (SE 10.4%), respectively; CIR 46.3% (SE 7.8%) and 50.9% (SE 12.3%). The most favorable treatment outcome was achieved in infants carrying translocation t(10;11)(p12;q23)/KMT2A-MLLT10: EFS 83.3% (SE 15.2%), CIR 0,0%. In the multivariate analysis unfavorable outcome of KMT2A-rearranged infant ALL was associated with initial CNS involvement (p = 0.020), initial white blood cell count higher than 300 × 109 /L (p = 0.028), more than 5% blast cells on day 15 in bone marrow (p = 0.012) and presence of translocation t(11;19)/KMT2A-MLLT1 (p = 0.012).

The purpose of this work was evaluation of prognostic significance of 11q23/KMT2A rearrangements in infants (aged under 365 days) with B-cell precursor acute lymphoblastic leukemia (ALL) enrolled in Russian-Belarus multicenter trial MLLBaby. This study is supported by the Independent Ethics Committee and approved by the Academic Council of the Research Institute of Medical Cell Technologies (Ekaterinburg). Various 11q23/KMT2A rearrangements were revealed in 100 (72%) of 139 patients. Event-free survival (EFS) in the intermediate risk group of MLL-Baby trial was 35.1% (standard error (SE) 6.9%), in the high risk group – 38.3% (SE 7.1%) (p = 0.941). The most unfavorable prognosis had infants with translocation t(9;11)/KMT2A-MLLT3: EFS 18.8% (SE 9.8%), cumulative incidence of relapse (CIR) 75.0% (SE 9.7%). Intermediate results were obtained in patients with translocations t(4;11)/KMT2A-AFF1 and t(11;19)/KMT2A-MLLT1: EFS 36.9% (SE 7,2%) and 32,7% (SE 10.4%), respectively; CIR 46.3% (SE 7.8%) and 50.9% (SE 12.3%). The most favorable treatment outcome was achieved in infants carrying translocation t(10;11)(p12;q23)/KMT2A-MLLT10: EFS 83.3% (SE 15.2%), CIR 0,0%. In the multivariate analysis unfavorable outcome of KMT2A-rearranged infant ALL was associated with initial CNS involvement (p = 0.020), initial white blood cell count higher than 300 × 109 /L (p = 0.028), more than 5% blast cells on day 15 in bone marrow (p = 0.012) and presence of translocation t(11;19)/KMT2A-MLLT1 (p = 0.012).

The prognostic value of minimal residual disease (MRD) measured by fusion-gene transcript (FGT) detection was investigated in 76 infants (aged ≤1 year) with acute lymphoblastic leukaemia (ALL) with lysine methyltransferase 2A (KMT2A) rearrangements. Either at the end of induction or at later time-points, FGT-MRD-positivity was associated with poor outcome. FGT-MRD-positivity after first consolidation or first high-risk block detected 46·5% of infants with extremely poor outcome [disease-free survival (SE) 0·06 (0·06), cumulative incidence of relapse (SE) 0·91 (0·05)], which was also confirmed in multivariable analysis. Thus, FGT-MRD measurement at a single time-point clearly identifies infants with ALL who are curable with conventional chemotherapy and those who would benefit only from other treatment approaches.