Two novel high-risk adult B-cell acute lymphoblastic leukemia subtypes with high expression of CDX2 and IDH1/2 mutations.

The genetic basis of leukemogenesis in adults with B-cell acute lymphoblastic leukemia (B-ALL) is largely unclear, and its clinical outcome remains unsatisfactory. This study aimed to advance the understanding of biological characteristics, improve disease stratification, and identify molecular targets of adult B-ALL. Adolescents and young adults (AYA) (15 to 39 years old, n = 193) and adults (40 to 64 years old, n = 161) with Philadelphia chromosome-negative (Ph-) B-ALL were included in this study. Integrated transcriptomic and genetic analyses were used to classify the cohort into defined subtypes. Of the 323 cases included in the RNA sequencing analysis, 278 (86.1%) were classified into 18 subtypes. The ZNF384 subtype (22.6%) was the most prevalent, with 2 novel subtypes (CDX2-high and IDH1/2-mut) identified among cases not assigned to the established subtypes. The CDX2-high subtype (3.4%) was characterized by high expression of CDX2 and recurrent gain of chromosome 1q. The IDH1/2-mut subtype (1.9%) was defined by IDH1 R132C or IDH2 R140Q mutations with specific transcriptional and high-methylation profiles. Both subtypes showed poor prognosis and were considered inferior prognostic factors independent of clinical parameters. Comparison with a previously reported pediatric B-ALL cohort (n = 1003) showed that the frequencies of these subtypes were significantly higher in AYA/adults than in children. We delineated the genetic and transcriptomic landscape of adult B-ALL and identified 2 novel subtypes that predict poor disease outcomes. Our findings highlight the age-dependent distribution of subtypes, which partially accounts for the prognostic differences between adult and pediatric B-ALL.

High DOCK1 expression identifies a distinct prognostic subgroup of pediatric acute myeloid leukemia: Results of the Japanese Pediatric Leukemia/Lymphoma Study Group AML-05 trial.

BACKGROUND: The molecular pathogenesis of acute myeloid leukemia (AML) was dramatically clarified over the latest two decades. Several important molecular markers were discovered in patients with AML that have helped to improve the risk stratification. However, developing new treatment strategies for relapsed/refractory acute myeloid leukemia (AML) is crucial due to its poor prognosis. PROCEDURE: To overcome this difficulty, we performed an assay for transposase-accessible chromatin with sequencing (ATAC-seq) in 10 AML patients with various gene alterations. ATAC-seq is based on direct in vitro sequencing adaptor transposition into native chromatin, and is a rapid and sensitive method for integrative epigenomic analysis. ATAC-seq analysis revealed increased accessibility of the DOCK1 gene in patients with AML harboring poor prognostic factors. Following the ATAC-seq results, quantitative reverse transcription polymerase chain reaction was used to measure DOCK1 gene expression levels in 369 pediatric patients with de novo AML. RESULTS: High DOCK1 expression was detected in 132 (37%) patients. The overall survival (OS) and event-free survival (EFS) among patients with high DOCK1 expression were significantly worse than those patients with low DOCK1 expression (3-year EFS: 34% vs. 60%, p < .001 and 3-year OS: 60% vs. 80%, p < .001). To investigate the significance of high DOCK1 gene expression, we transduced DOCK1 into MOLM14 cells, and revealed that cytarabine in combination with DOCK1 inhibitor reduced the viability of these leukemic cells. CONCLUSIONS: Our results indicate that a DOCK1 inhibitor might reinforce the effects of cytarabine and other anti-cancer agents in patients with AML with high DOCK1 expression.

High IL2RA/CD25 expression is a prognostic stem cell biomarker for pediatric acute myeloid leukemia without a core-binding factor.

CD25 is an aberrant marker expressed on the leukemic stem cell (LSC) surface and an immunotherapy target in acute myeloid leukemia (AML). However, the clinical prevalence and significance of CD25 expression in pediatric AML are unknown. High IL2RA/CD25 expression in pediatric AML showed a stem cell-like phenotype, and elevated CD25 expression was associated with lower overall survival (p < .001) and event-free survival (p < .001) in the Japanese Pediatric Leukemia/Lymphoma Study Group AML-05 study. This finding was reproduced in AML without a core-binding factor in the Children's Oncology Group study cohort. High CD25 expression has prognostic significance in pediatric AML.

Development and evaluation of a rapid one-step high sensitivity real-time quantitative PCR system for minor BCR-ABL (e1a2) test in Philadelphia-positive acute lymphoblastic leukemia (Ph+ ALL).

OBJECTIVE: Minimal residual disease assessment of BCR-ABL messenger ribonucleic acid levels is crucial in Philadelphia chromosome-positive acute lymphoblastic leukemia for prognosis and treatment planning. However, accurately quantifying minor BCR-ABL transcripts, which comprise 70% of Philadelphia chromosome-positive acute lymphoblastic leukemia cases, lacks a national-approved method. METHODS: We developed the "Otsuka" minor BCR-ABLmessenger ribonucleic acid assay kit with exceptional precision (0.00151%). Minor BCR-ABL messenger ribonucleic acid levels were analyzed in 175 adults, 36 children with acute lymphoblastic leukemia and 25 healthy individuals to evaluate the kit's performance. RESULTS: The "Otsuka" kit showed high concordance with a commonly used chimeric gene screening method, indicating reliable detection of positive cases. Quantitative results demonstrated a robust correlation with both a laboratory-developed test and a diagnostic research product. The "Otsuka" kit performs comparably or even surpass to conventional products, providing valuable insights into Philadelphia chromosome-positive acute lymphoblastic leukemia pathology. CONCLUSIONS: The 'Otsuka" minor BCR-ABL messenger ribonucleic acid assay kit exhibits excellent performance in quantifying minor BCR-ABL transcripts in Philadelphia chromosome-positive acute lymphoblastic leukemia patients. Our results align well with established screening methods and show a strong correlation with laboratory-developed tests and diagnostic research products. The "Otsuka" kit holds great promise as a valuable tool for understanding Philadelphia chromosome-positive acute lymphoblastic leukemia pathology and guiding effective treatment strategies.

UBTF-internal tandem duplication as a novel poor prognostic factor in pediatric acute myeloid leukemia.

The prognosis of pediatric acute myeloid leukemia (AML) has improved via stratification therapy. However, relapse or death occurs in 30%-40% of cases. Novel genetic factors for pediatric AML need to be elucidated to improve prognosis. We detected recurrent internal tandem duplication in upstream binding transcription factor (UBTF-ITD) in 1.2% (6/503) of Japanese pediatric patients with de novo AML. No UBTF-ITD was detected in 175 adult patients with AML or in 65 cell lines that included 15 AML, 39 acute lymphoblastic leukemia, five chronic myeloid leukemia, and six neuroblastoma cell lines. All UBTF-ITDs were found in exon 13 and shared a duplicated region. UBTF-ITD was more frequently detected in patients with trisomy 8, FLT3-ITD, WT1 mutation, and/or high PRDM16 expression (trisomy 8, 3/6; FLT3-ITD, 5/6; WT1 mutation, 2/6; and high PRDM16 expression, 6/6). Gene expression patterns of patients with UBTF-ITD were similar to those of patients with NUP98::NSD1 or FUS::ERG. Survival analysis of the AML-05 cohort revealed that patients with UBTF-ITD had worse outcomes than those without UBTF-ITD (3-year event-free survival, 20% vs. 55%; 3-year overall survival, 40% vs. 74%). Moreover, among the 27 patients with trisomy 8, all three patients with UBTF -ITD had a poor prognosis resulting in early events (relapse or non-complete remission) within 1 year. Our findings suggest that UBTF-ITD may be a novel and significant prognostic factor for pediatric patients with AML.

TP53 and RB1 alterations characterize poor prognostic subgroups in pediatric acute myeloid leukemia.

Pediatric acute myeloid leukemia (AML) is a poor prognostic subtype of pediatric leukemia. However, the detailed characteristics of many genetic abnormalities are yet to be established in this disease. Although TP53 and RB1 are established as representative tumor suppressor genes in various cancers, alterations of these two genes, especially RB1, have not been characterized in pediatric AML. We performed next-generation sequencing in 328 pediatric AML patients from the Japanese AML-05 trial to ascertain TP53 and RB1 alterations, and their prognostic implications. We identified seven patients with TP53 alterations (2.1%) and six patients with RB1 alterations (1.8%). These alterations were found in only patients without RUNX1::RUNX1T1, CBFB::MYH11, or KMT2A rearrangements. TP53 and RB1 were frequently co-deleted with their neighboring genes PRPF8 and ELF1, respectively. Patients with TP53 alterations had significantly lower 5-year overall survival (OS; 14.3% vs. 71.4%, p < 0.001) and lower 5-year event-free survival (EFS; 0% vs. 56.3%, p < 0.001); similarly, patients with RB1 had significantly lower 5-year OS (0% vs. 71.8%, p < 0.001) and lower 5-year EFS (0% vs. 56.0%, p < 0.001) when compared to patients without these alterations. In gene expression analyses, oxidative phosphorylation, glycolysis, and protein secretion were upregulated in patients with TP53 and/or RB1 alterations. Additionally, Kaplan-Meier analysis revealed that high expressions of SLC2A5, KCNAB2, and CD300LF were related to poor OS of non-core-binding factor AML patients (p < 0.001, p = 0.001, and p = 0.021, respectively). This study will contribute to the development of risk-stratified therapy and precision medicine in pediatric AML.

[Experience with an international study on standard-risk relapsed childhood acute lymphoblastic leukemia (IntReALL SR 2010 study) in Japan].

Many effective new agents for relapsed childhood acute lymphoblastic leukemia (ALL) are now becoming available, and international standard chemotherapy should be developed to optimize use of these agents. Randomized controlled trials (RCTs) are needed to establish a standard treatment, but few have been conducted for relapsed childhood ALL in Japan due to the small patient population. Participation in international RCTs is necessary to access sufficient patients for informative study results, but differences in approved drugs and healthcare systems between countries make this challenging. In 2014, the Japanese Pediatric Leukemia/Lymphoma Study Group (JPLSG) participated in an international study on standard-risk relapsed childhood ALL (IntReALL SR 2010) involving two RCTs and multiple drugs not approved in Japan, which was addressed by replacing the unapproved drugs with alternative approved drugs with the same or similar efficacy. This article discusses the historical background of treatment development for relapsed childhood ALL, our experience in participating in the IntReALL SR 2010 trial, and prospects for treating relapsed childhood ALL.

Impact of asparaginase discontinuation on outcomes of children with acute lymphoblastic leukaemia receiving the Japan Association of Childhood Leukaemia Study ALL-02 protocol.

Asparaginase is an essential drug for acute lymphoblastic leukaemia (ALL) treatment, but has several side effects, and its discontinuation often compromises patient outcomes. In the prospective Japan Association of Childhood Leukaemia Study ALL-02 protocol, two major changes were made: (1) additional chemotherapies to compensate for the reduction of treatment intensity when asparaginase was discontinued and (2) more intensive concomitant corticosteroid administration, relative to our previous ALL-97 protocol. In ALL-02 study, 1192 patients were included and L-asparaginase was discontinued for 88 (7.4%). Discontinuation due to allergy was markedly decreased relative to the ALL-97 protocol (2.3% vs 15.4%). Event-free survival (EFS) among patients with T-ALL was compromised when L-asparaginase was discontinued, as well as among patients with high-risk B-cell ALL, especially when discontinued before maintenance therapy. Moreover, multivariate analysis identified discontinuation of L-asparaginase as an independent poor prognostic factor for EFS. In the current study, additional chemotherapies failed to fully compensate for L-asparaginase discontinuation, illustrating the difficulty of replacing asparaginase with other classes of drugs, although this study was not designed to evaluate the effect of these modifications. Concomitant intensive corticosteroid treatment may help to reduce allergy to asparaginase. These results will assist in further optimization of asparaginase use.

Feasibility and preliminary effectiveness of a psychosocial support program for adolescent and young adult cancer patients in clinical practice: a retrospective observational study.

PURPOSE: Adolescent and young adult cancer patients (AYAs) often experience profound psychological distress, with various unmet supportive care needs that can be alleviated with appropriate screening and attention by healthcare workers. The Distress Thermometer and Problem List-Japanese version (DTPL-J) is our previously developed screening tool to facilitate individual support of AYAs. This study evaluated the feasibility and preliminary effectiveness of a psychosocial support program based on the DTPL-J for AYAs in clinical practice. METHODS: This multicenter, retrospective, observational study included 19 of 126 wards and 9 of 75 outpatient clinics at 8 institutions in Japan. Over 200 patients were expected to participate during the eligibility period. Patients participated in a support program at least once, and approximately once a month based on the DTPL-J results. The program was evaluated using the RE-AIM (Reach, Effectiveness, Adoption, Implementation, and Maintenance) implementation framework. RESULTS: The screening rate of the 361 participants was 90.3%, suggesting high feasibility. Distress Thermometer scores, the number of supportive care needs, and the rates of AYAs with high distress were significantly reduced 1 month after screening (p < 0.05), suggesting the preliminary effectiveness of the program. The program was continued at the 8 institutions as part of routine care after the study. CONCLUSION: Analysis using the RE-AIM suggested the sufficient feasibility and preliminary effectiveness of a psychosocial support program based on the DTPL-J for AYAs. TRIAL REGISTRATION: University Hospital Medical Information Network (UMIN CTR) UMIN000042857. Registered 25 December 2020-Retrospectively registered.

Medical staff's sense of awareness of informed consent for adolescent cancer patients and the need for decision-making support practiced from the perspective of trauma-informed approach.

It has not been established how to assess children's and adolescents' decision-making capacity (DMC) and there has been little discussion on the way their decision-making (DM). The purpose of this study was to examine actual situation and factors related to difficulties in explaining their disease to adolescent cancer patients or obtaining informed consent (IC). The cross-sectional questionnaire survey was conducted. Physicians who have been treating adolescent cancer patients for at least five years answered a self-administered questionnaire uniquely developed about clinical difficulties in explaining, IC and factors related patient's refusal of medical treatment (RMT). Descriptive statistics for each item and a polychoric correlation analysis of the problems and factors related to the explanation were conducted. As a result, fifty-six physicians were participated (rate of return: 39%). Explaining the disease and treatment to patients (83.9%), IC to patients (80.4%), and explaining the disease and treatment to parents (78.6%) was particularly problematic. Difficulties to provide support related with patient's refusal of medical treatment and to explain disease and treatment for patient and parents were related to difficulties obtaining IC for the patient. Conclusion: There are clinically difficult to explain for the patient or parents and to obtain IC for the patient. It is necessary to establish a disease acceptance assessment tool for the adolescence generation so that it can be applied in the field.

The incidence of symptomatic osteonecrosis is similar between Japanese children and children in Western countries with acute lymphoblastic leukaemia treated with a Berlin-Frankfurt-Münster (BFM)95-based protocol.

In this study, we performed a retrospective analysis of a cohort of Japanese paediatric patients with B-cell precursor (BCP)-acute lymphoblastic leukaemia (ALL) treated with a Berlin-Frankfurt-Münster (BFM)95-based protocol, to clarify the incidence, clinical characteristics, and risk factors of osteonecrosis (ON) in comparison to the ALL-02 protocol. We identified a high frequency of ON with the BFM95-based protocol compared to the ALL-02 protocol. The incidence of symptomatic ON with the BFM95-based protocol is comparable to previous studies in Western countries. We believe that the type of treatment regimen has more impact on the incidence of symptomatic ON in paediatric ALL than ethnicity.

A risk-stratified therapy for infants with acute lymphoblastic leukemia: a report from the JPLSG MLL-10 trial.

The prognosis for infants with acute lymphoblastic leukemia (ALL), particularly those with KMT2A gene rearrangement (KMT2A-r), is dismal. Continuous efforts have been made in Japan to investigate the role of hematopoietic stem cell transplantation (HSCT) for infants with KMT2A-r ALL, but improvement in outcome was modest. In the Japanese Pediatric Leukemia/Lymphoma Study Group MLL-10 trial, infants with ALL were stratified into 3 risk groups (low risk [LR], intermediate risk [IR], and high risk [HR]) according to KMT2A status, age, and presence of central nervous system leukemia. Children's Oncology Group AALL0631 modified chemotherapy with the addition of high-dose cytarabine in early intensification was introduced to KMT2A-r patients, and the option of HSCT was restricted to HR patients only. The role of minimal residual disease (MRD) was also evaluated. Ninety eligible infants were stratified into LR (n = 15), IR (n = 19), or HR (n = 56) risk groups. The 3-year event-free survival (EFS) rate for patients with KMT2A-r ALL (IR + HR) was 66.2% (standard error [SE], 5.6%), and for those with germline KMT2A (KMT2A-g) ALL (LR), the 3-year EFS rate was 93.3% (SE, 6.4%). The 3-year EFS rate was 94.4% (SE, 5.4%) for IR patients and 56.6% (SE, 6.8%) for HR patients. In multivariable analysis, female sex and MRD ≥0.01% at the end of early consolidation were significant factors for poor prognosis. Risk stratification and introduction of intensive chemotherapy in this study were effective and were able to eliminate HSCT for a subset of infants with KMT2A-r ALL. Early clearance of MRD seems to have translated into favorable outcomes and should be incorporated into risk stratifications in future trials. This trial was registered at the University Hospital Medical Information Network Clinical Trials Registry (UMIN-CTR) as #UMIN000004801.

Clinical significance of RAS pathway alterations in pediatric acute myeloid leukemia.

RAS pathway alterations have been implicated in the pathogenesis of various hematological malignancies. However, their clinical relevance in pediatric acute myeloid leukemia (AML) is not well characterized. We analyzed the frequency, clinical significance, and prognostic relevance of RAS pathway alterations in 328 pediatric patients with de novo AML. RAS pathway alterations were detected in 80 (24.4%) of 328 patients: NF1 (n=7, 2.1%), PTPN11 (n=15, 4.6%), CBL (n=6, 1.8%), NRAS (n=44, 13.4%), KRAS (n=12, 3.7%). Most of these alterations in the RAS pathway were mutually exclusive also together with other aberrations of signal transduction pathways such as FLT3-ITD (P=0.001) and KIT mutation (P=0.004). NF1 alterations were frequently detected in patients with complex karyotype (P=0.031) and were found to be independent predictors of poor overall survival (OS) in multivariate analysis (P=0.007). At least four of seven patients with NF1 alterations had biallelic inactivation. NRAS mutations were frequently observed in patients with CBFB-MYH11 and were independent predictors of favorable outcomes in multivariate analysis (OS, P=0.023; event-free survival [EFS], P=0.037). Patients with PTPN11 mutations more frequently received stem cell transplantation (P=0.035) and showed poor EFS than patients without PTPN11 mutations (P=0.013). Detailed analysis of RAS pathway alterations may enable a more accurate prognostic stratification of pediatric AML and may provide novel therapeutic molecular targets related to this signal transduction pathway.

Safety and Efficacy of Blinatumomab in Japanese Adult and Pediatric Patients with Relapsed/Refractory B-Cell Precursor Acute Lymphoblastic Leukemia: Final Results from an Expansion Cohort.

INTRODUCTION: The safety and efficacy of blinatumomab, a CD19/CD3 bispecific T-cell engager (BiTE®) molecule, was evaluated in an expansion cohort of the phase 1b/2 study (NCT02412306) in Japanese adult (n = 14) and pediatric (n = 17) patients with relapsed/refractory Philadelphia-negative B-cell precursor (BCP) acute lymphoblastic leukemia (ALL). MATERIALS AND METHODS: Globally recommended blinatumomab doses were administered to adult (9-28 µg/day) and pediatric (5-15 µg/m2/day) patients. Primary endpoint was the incidence of treatment-emergent adverse events (TEAEs) and treatment-related AEs. RESULTS: All adult and pediatric patients experienced ≥1 TEAE. Grade ≥3 TEAEs were observed in 11 (79%) adult and 15 (88%) pediatric patients. Blinatumomab was discontinued in 1 (6%) pediatric patient due to treatment-related grade 4 cytokine release syndrome. Fatal AEs such as disease progression and multiple-organ dysfunction syndrome, which were not treatment-related, were reported in 2 (12%) pediatric patients. Eleven (79%) adults achieved complete remission (CR)/CR with partial hematological recovery (CRh) within the first two blinatumomab cycles. Nine of 10 adult patients with CR/CRh and evaluable minimal residual disease (MRD) achieved MRD response. CR/CRh was achieved by 5 (29%) pediatric patients, of which two had MRD response. CONCLUSION: In conclusion, blinatumomab was safe and efficacious in Japanese patients with relapsed/refractory BCP ALL.

Gemtuzumab Ozogamicin Followed by Unrelated Cord Blood Transplantation With Reduced-intensity Conditioning for a Child With Refractory Acute Promyelocytic Leukemia.

There is no established treatment for patients with acute promyelocytic leukemia (APL) refractory to targeted therapies with all-trans retinoic acid (ATRA) and/or arsenic trioxide (ATO). We report here a case of an 8-month-old girl with APL who failed standard ATRA-combined chemotherapy. Although molecular remission was achieved after introducing ATRA/ATO combination therapy, molecular relapse occurred during the ATO consolidation courses. Subsequent molecular remission was rapidly achieved after administering 2 doses of gemtuzumab ozogamicin. She was successfully treated with unrelated cord blood transplantation using reduced-intensity conditioning. Gemtuzumab ozogamicin might be a preferable choice for patients with APL refractory to standard therapy.

Cancer in adolescents and young adults in Japan: epidemiology and cancer strategy.

According to national cancer registry data in Japan, approximately 20,000 adolescents and young adults (AYAs, age 15-39 years) are newly diagnosed with cancer each year. Improvements in treatment and care for AYAs with cancer are included in the Phase Three Basic Plan to Promote Cancer Control Programs in Japan. This article reviews current cancer incidence and survival for AYAs with cancer in Japan using population-based cancer registry data. Mortality data through 2019 from the Vital Statistics of Japan are also described. Encouragingly, the 5-year survival probability for AYA cancers has continued to improve, in parallel with childhood cancers, and the mortality rate has decreased. There has been increasing attention to these vulnerable patients and improved partnerships and collaboration between adult and pediatric oncology; however, obstacles to the care of this population still exist at multiple levels. These obstacles relate to specific areas: research efforts and enrollment in clinical trials on AYA malignancies, AYA-specific psychosocial support such as education, financial support, and oncofertility care, and cancer care systems. It is important for Japanese oncologists, health care providers, and health policy makers to recognize that the AYA population remains vulnerable and still have unmet needs.

Differences in the approaches of cancer specialists toward adolescent and young adult cancer care.

BACKGROUND: This study investigated the medical care of adolescent and young adult (AYA) cancer patients and compared approaches toward AYA cancer care by pediatric and adult cancer specialists. METHODS: An Internet survey was conducted among 1,305 specialists (192 pediatric and 1,109 adult) in 2016. RESULTS: The rate of awareness of the term "AYA" was lower for adult specialists than for pediatric specialists. The departments that are responsible for caring for AYA cancer patients change when they reach 20 years of age. For the treatment of AYA patients, both pediatric and adult specialists preferred a multidisciplinary team as a top priority issue. A special ward or hospital rooms for AYA was required mostly for AYA patients under 24, and the needs for special wards or rooms for AYA was higher in pediatric specialists than in adult specialists. However, for AYA patients over 25, about 60% of adult specialists and 35% of pediatric specialists believed that no special care was required. As for desirable follow-up protocols for pediatric cancer AYA survivors, half of the specialists considered that they should be conducted mainly by pediatric specialists in cooperation with adult specialists, and 30% to 40% of the specialists considered that transition to the corresponding adult medicine department would be preferable. CONCLUSIONS: There were obvious differences in medical care and support for AYA cancer patients according to their age, particularly under the age of 20 or 24, and according to whether the onset of disease occurred during the AYA period or whether it was secondary to pediatric cancers. For each aspect, appropriate programs would require close cooperation between pediatric and adult specialists.

Neuro-meningeal relapse in anaplastic large-cell lymphoma: incidence, risk factors and prognosis - a report from the European intergroup for childhood non-Hodgkin lymphoma.

Relapses involving the central nervous system (CNS) are rare in children and adolescents with ALK+ anaplastic large cell lymphoma (ALCL) treated with regimens including CNS prophylaxis. Early identification of patients at high-risk for CNS relapse would enable stratification and better adaptation of initial treatment especially in the light of the upcoming targeted therapies with limited CNS penetration. We analyzed clinical and histological data of all ALK+ALCL patients with CNS relapse registered in ALCL99-database with the aim to describe risk factors and outcome. Characteristics of patients with no relapse, relapse without CNS involvement and CNS relapse were compared. At a median follow-up of 8 years (0.05-18 years), a CNS involvement was reported at first or subsequent relapse in 26/618 patients. Median interval between initial diagnosis and first CNS relapse was 8 months (IQR 5.55-10.61/range 1.31-130.69). The 5-year cumulative risk of CNS relapse was 4% (95% CI 2.9-5.5). Bone marrow involvement, peripheral blasts and CNS involvement at diagnosis were more frequent in patients with CNS relapse than in patients with no relapse or with relapse with no CNS involvement. The treatment of CNS relapse was heterogeneous. The median survival after CNS relapse was 23.7 months. Eleven patients were alive at last follow-up. Three-year overall survival after CNS relapse was 48.70% (95% CI 30.52-67.23).

Predisposition to prolonged neutropenia after chemotherapy for paediatric acute myeloid leukaemia is associated with better prognosis in the Japanese Paediatric Leukaemia/Lymphoma Study Group AML-05 study.

The variability in myelosuppression after chemotherapy for acute myeloid leukaemia (AML) can affect its prognosis; however, the underlying mechanism remains controversial. In the Japanese Paediatric Leukaemia/Lymphoma Study Group AML-05 study, we showed that prolonged neutropenia was associated with high overall survival (P = 0·011) and low frequency of relapse (P = 0·042) in patients without granulocyte-colony stimulating factor (G-CSF) who completed the indicated treatment protocol. Our data indicate that predisposition to prolonged neutropenia after chemotherapy is correlated with a better outcome of AML treatment. Our results promote the usage of individualised drug dosing strategies to improve the therapeutic outcome in AML patients.

Droplet digital polymerase chain reaction assay for the detection of the minor clone of KIT D816V in paediatric acute myeloid leukaemia especially showing RUNX1-RUNX1T1 transcripts.

KIT D816V mutation within exon 17 has been particularly reported as one of the poor prognostic factors in pediatric acute myeloid leukemia (AML) with RUNX1-RUNX1T1. The exact frequency and the prognostic impact of KIT D816V minor clones at diagnosis were not examined. In this study, the minor clones were examined and the prognostic significance of KIT D816V mutation in pediatric patients was investigated. Consequently, 24 KIT D816V mutations (7.2%) in 335 pediatric patients were identified, and 12 of 24 were only detected via the digital droplet polymerase chain reaction method. All 12 patients were confined in core binding factor (CBF)-AML patients. The 5 year event-free survival of the patients with KIT D816V mutation was significantly inferior to those without KIT D816V mutation (44.1% [95% confidence interval (CI), 16.0%-69.4%] vs. 74.7% [95% CI, 63.0%-83.2%] P-value = 0.02, respectively). The 5 year overall survival was not different between the two groups (92.9% [95% CI, 59.0%-NA vs. 89.7% [95% CI, 69.6%-96.8%] P-value = 0.607, respectively). In this study, KIT D816V minor clones in patients with CBF-AML were confirmed and KIT D816V was considered as a risk factor for relapse in patients with RUNX1-RUNX1T1-positive AML.