Response to upfront azacitidine in juvenile myelomonocytic leukemia in the AZA-JMML-001 trial.

Allogeneic hematopoietic stem cell transplantation (HSCT) is the only curative therapy for most children with juvenile myelomonocytic leukemia (JMML). Novel therapies controlling the disorder prior to HSCT are needed. We conducted a phase 2, multicenter, open-label study to evaluate the safety and antileukemic activity of azacitidine monotherapy prior to HSCT in newly diagnosed JMML patients. Eighteen patients enrolled from September 2015 to November 2017 were treated with azacitidine (75 mg/m2) administered IV once daily on days 1 to 7 of a 28-day cycle. The primary end point was the number of patients with clinical complete remission (cCR) or clinical partial remission (cPR) after 3 cycles of therapy. Pharmacokinetics, genome-wide DNA-methylation levels, and variant allele frequencies of leukemia-specific index mutations were also analyzed. Sixteen patients completed 3 cycles and 5 patients completed 6 cycles. After 3 cycles, 11 patients (61%) were in cPR and 7 (39%) had progressive disease. Six of 16 patients (38%) who needed platelet transfusions were transfusion-free after 3 cycles. All 7 patients with intermediate- or low-methylation signatures in genome-wide DNA-methylation studies achieved cPR. Seventeen patients received HSCT; 14 (82%) were leukemia-free at a median follow-up of 23.8 months (range, 7.0-39.3 months) after HSCT. Azacitidine was well tolerated and plasma concentration--time profiles were similar to observed profiles in adults. In conclusion, azacitidine monotherapy is a suitable option for children with newly diagnosed JMML. Although long-term safety and efficacy remain to be fully elucidated in this population, these data demonstrate that azacitidine provides valuable clinical benefit to JMML patients prior to HSCT. This trial was registered at www.clinicaltrials.gov as #NCT02447666.

High-resolution pediatric reference intervals for 15 biochemical analytes described using fractional polynomials.

OBJECTIVES: Assessment of children's laboratory test results requires consideration of the extensive changes that occur during physiological development and result in pronounced sex- and age-specific dynamics in many biochemical analytes. Pediatric reference intervals have to account for these dynamics, but ethical and practical challenges limit the availability of appropriate pediatric reference intervals that cover children from birth to adulthood. We have therefore initiated the multi-center data-driven PEDREF project (Next-Generation Pediatric Reference Intervals) to create pediatric reference intervals using data from laboratory information systems. METHODS: We analyzed laboratory test results from 638,683 patients (217,883-982,548 samples per analyte, a median of 603,745 test results per analyte, and 10,298,067 test results in total) performed during patient care in 13 German centers. Test results from children with repeat measurements were discarded, and we estimated the distribution of physiological test results using a validated statistical approach (kosmic). RESULTS: We report continuous pediatric reference intervals and percentile charts for alanine transaminase, aspartate transaminase, lactate dehydrogenase, alkaline phosphatase, γ-glutamyl-transferase, total protein, albumin, creatinine, urea, sodium, potassium, calcium, chloride, anorganic phosphate, and magnesium. Reference intervals are provided as tables and fractional polynomial functions (i.e., mathematical equations) that can be integrated into laboratory information systems. Additionally, Z-scores and percentiles enable the normalization of test results by age and sex to facilitate their interpretation across age groups. CONCLUSIONS: The provided reference intervals and percentile charts enable precise assessment of laboratory test results in children from birth to adulthood. Our findings highlight the pronounced dynamics in many biochemical analytes in neonates, which require particular consideration in reference intervals to support clinical decision making most effectively.

International Consensus Definition of DNA Methylation Subgroups in Juvenile Myelomonocytic Leukemia.

PURPOSE: Known clinical and genetic markers have limitations in predicting disease course and outcome in juvenile myelomonocytic leukemia (JMML). DNA methylation patterns in JMML have correlated with outcome across multiple studies, suggesting it as a biomarker to improve patient stratification. However, standardized approaches to classify JMML on the basis of DNA methylation patterns are lacking. We, therefore, sought to define an international consensus for DNA methylation subgroups in JMML and develop classification methods for clinical implementation. EXPERIMENTAL DESIGN: Published DNA methylation data from 255 patients with JMML were used to develop and internally validate a classifier model. Accuracy across platforms (EPIC-arrays and MethylSeq) was tested using a technical validation cohort (32 patients). The suitability of both methods for single-patient classification was demonstrated using an independent cohort (47 patients). RESULTS: Analysis of pooled, published data established three DNA methylation subgroups as a de facto standard. Unfavorable prognostic parameters (PTPN11 mutation, elevated fetal hemoglobin, and older age) were significantly enriched in the high methylation (HM) subgroup. A classifier was then developed that predicted subgroups with 98% accuracy across different technological platforms. Applying the classifier to an independent validation cohort confirmed an association of HM with secondary mutations, high relapse incidence, and inferior overall survival (OS), while the low methylation subgroup was associated with a favorable disease course. Multivariable analysis established DNA methylation subgroups as the only significant factor predicting OS. CONCLUSIONS: This study provides an international consensus definition for DNA methylation subgroups in JMML. We developed and validated methods which will facilitate the design of risk-stratified clinical trials in JMML.

Patterns of Prior and Subsequent Neoplasms in Children and Adolescents With Soft Tissue Sarcomas.

BACKGROUND: The occurrence of prior, concurrent and subsequent neoplasms (SN) represents a serious problem in children and adolescents with soft tissue sarcomas. Pathogenic germline variants contribute to the diagnosis of multiple neoplasms in sarcoma survivors. MATERIALS AND METHODS: The records of 748 children and adolescents, diagnosed with soft tissue sarcomas and registered in trials/registries by the cooperative soft tissue sarcoma (Cooperative Weichteilsarkom Studie) group, were reviewed for the occurrence of SNs. Reference histology review was available for all cases; the presence of oncogenic fusions known at the time of diagnosis was confirmed for fusion-positive (F+) entities. RESULTS: Concurrent or subsequent SNs developed in 13 of 473 survivors of fusion-negative (F-) sarcomas, for an 8-year cumulative SN incidence of 5% in survivors of F- sarcomas. In contrast, only 1 of 278 survivors of F+ sarcoma developed an SN. Twenty of 748 patients with soft tissue sarcomas had a history of prior neoplasms. Six of 14 patients who developed SNs after their index sarcomas met Chompret criteria for Li-Fraumeni syndrome. Nine of 20 patients who had tumors before their index sarcoma diagnosis had neurofibromatosis type 1 or neurofibromatosis type 1 spectrum tumors. CONCLUSION: Sarcoma phenotype/genotype and the sequence and nature of prior and subsequent neoplasms provide a window into underlying germline genetic susceptibilities in children and adolescents with soft tissue sarcomas.

Next-generation reference intervals for pediatric hematology.

Background Interpreting hematology analytes in children is challenging due to the extensive changes in hematopoiesis that accompany physiological development and lead to pronounced sex- and age-specific dynamics. Continuous percentile charts from birth to adulthood allow accurate consideration of these dynamics. However, the ethical and practical challenges unique to pediatric reference intervals have restricted the creation of such percentile charts, and limitations in current approaches to laboratory test result displays restrict their use when guiding clinical decisions. Methods We employed an improved data-driven approach to create percentile charts from laboratory data collected during patient care in 10 German centers (9,576,910 samples from 358,292 patients, 412,905-1,278,987 samples per analyte). We demonstrate visualization of hematology test results using percentile charts and z-scores (www.pedref.org/hematology) and assess the potential of percentiles and z-scores to support diagnosis of different hematological diseases. Results We created percentile charts for hemoglobin, hematocrit, red cell indices, red cell count, red cell distribution width, white cell count and platelet count in girls and boys from birth to 18 years of age. Comparison of pediatricians evaluating complex clinical scenarios using percentile charts versus conventional/tabular representations shows that percentile charts can enhance physician assessment in selected example cases. Age-specific percentiles and z-scores, compared with absolute test results, improve the identification of children with blood count abnormalities and the discrimination between different hematological diseases. Conclusions The provided reference intervals enable precise assessment of pediatric hematology test results. Representation of test results using percentiles and z-scores facilitates their interpretation and demonstrates the potential of digital approaches to improve clinical decision-making.

RAS-pathway mutation patterns define epigenetic subclasses in juvenile myelomonocytic leukemia.

Juvenile myelomonocytic leukemia (JMML) is an aggressive myeloproliferative disorder of early childhood characterized by mutations activating RAS signaling. Established clinical and genetic markers fail to fully recapitulate the clinical and biological heterogeneity of this disease. Here we report DNA methylome analysis and mutation profiling of 167 JMML samples. We identify three JMML subgroups with unique molecular and clinical characteristics. The high methylation group (HM) is characterized by somatic PTPN11 mutations and poor clinical outcome. The low methylation group is enriched for somatic NRAS and CBL mutations, as well as for Noonan patients, and has a good prognosis. The intermediate methylation group (IM) shows enrichment for monosomy 7 and somatic KRAS mutations. Hypermethylation is associated with repressed chromatin, genes regulated by RAS signaling, frequent co-occurrence of RAS pathway mutations and upregulation of DNMT1 and DNMT3B, suggesting a link between activation of the DNA methylation machinery and mutational patterns in JMML.

CREBBP is a target of epigenetic, but not genetic, modification in juvenile myelomonocytic leukemia.

BACKGROUND: Juvenile myelomonocytic leukemia (JMML) is a myeloproliferative neoplasm of childhood whose clinical heterogeneity is only poorly represented by gene sequence alterations. It was previously shown that aberrant DNA methylation of distinct target genes defines a more aggressive variant of JMML, but only few significant targets are known so far. To get a broader picture of disturbed CpG methylation patterns in JMML, we carried out a methylation screen of 34 candidate genes in 45 patients using quantitative mass spectrometry. FINDINGS: Five of 34 candidate genes analyzed showed recurrent hypermethylation in JMML. cAMP-responsive element-binding protein-binding protein (CREBBP) was the most frequent target of epigenetic modification (77 % of cases). However, no pathogenic mutations of CREBBP were identified in a genetic analysis of 64 patients. CREBBP hypermethylation correlated with clinical parameters known to predict poor outcome. CONCLUSIONS: This study supports the relevance of epigenetic aberrations in JMML pathophysiology. Our data confirm that DNA hypermethylation in JMML is highly target-specific and associated with higher-risk features. These findings encourage the development of prognostic markers based on epigenetic alterations, which will be helpful in the difficult clinical management of this heterogeneous disease.

Epigenetic silencing of AKAP12 in juvenile myelomonocytic leukemia.

A-kinase anchor protein 12 (AKAP12) is a regulator of protein kinase A and protein kinase C signaling, acting downstream of RAS. Epigenetic silencing of AKAP12 has been demonstrated in different cancer entities and this has been linked to the process of tumorigenesis. Here, we used quantitative high-resolution DNA methylation measurement by MassARRAY to investigate epigenetic regulation of all three AKAP12 promoters (i.e., α, ß, and γ) within a large cohort of juvenile myelomonocytic leukemia (JMML) patient samples. The AKAP12α promoter shows DNA hypermethylation in JMML samples, which is associated with decreased AKAP12α expression. Promoter methylation of AKAP12α correlates with older age at diagnosis, elevated levels of fetal hemoglobin and poor prognosis. In silico screening for transcription factor binding motifs around the sites of most pronounced methylation changes in the AKAP12α promoter revealed highly significant scores for GATA-2/-1 sequence motifs. Both transcription factors are known to be involved in the haematopoietic differentiation process. Methylation of a reporter construct containing this region resulted in strong suppression of AKAP12 promoter activity, suggesting that DNA methylation might be involved in the aberrant silencing of the AKAP12 promoter in JMML. Exposure to DNMT- and HDAC-inhibitors reactivates AKAP12α expression in vitro, which could potentially be a mechanism underlying clinical treatment responses upon demethylating therapy. Together, these data provide evidence for epigenetic silencing of AKAP12α in JMML and further emphasize the importance of dysregulated RAS signaling in JMML pathogenesis.

RASA4 undergoes DNA hypermethylation in resistant juvenile myelomonocytic leukemia.

Aberrant DNA methylation at specific genetic loci is a key molecular feature of juvenile myelomonocytic leukemia (JMML) with poor prognosis. Using quantitative high-resolution mass spectrometry, we identified RASA4 isoform 2, which maps to chromosome 7 and encodes a member of the GAP1 family of GTPase-activating proteins for small G proteins, as a recurrent target of isoform-specific DNA hypermethylation in JMML (51% of 125 patients analyzed). RASA4 isoform 2 promoter methylation correlated with clinical parameters predicting poor prognosis (older age, elevated fetal hemoglobin), with higher risk of relapse after hematopoietic stem cell transplantation, and with PTPN11 mutation. The level of isoform 2 methylation increased in relapsed cases after transplantation. Interestingly, most JMML cases with monosomy 7 exhibited hypermethylation on the remaining RASA4 allele. The results corroborate the significance of epigenetic modifications in the phenotype of aggressive JMML.

Comparison of horse and rabbit antithymocyte globulin in immunosuppressive therapy for refractory cytopenia of childhood.

Refractory cytopenia of childhood is the most common subtype of myelodysplastic syndrome in children. In this study, we compared the outcome of immunosuppressive therapy using horse antithymocyte globulin (n=46) with that using rabbit antithymocyte globulin (n=49) in 95 patients with refractory cytopenia of childhood and hypocellular bone marrow. The response rate at 6 months was 74% for horse antithymocyte globulin and 53% for rabbit antithymocyte globulin (P=0.04). The inferior response in the rabbit antithymocyte globulin group resulted in lower 4-year transplantation-free (69% versus 46%; P=0.003) and failure-free (58% versus 48%; P=0.04) survival rates in this group compared with those in the horse antithymocyte globulin group. However, because of successful second-line hematopoietic stem cell transplantation, overall survival was comparable between groups (91% versus 85%; P=ns). The cumulative incidence of relapse (15% versus 9%; P=ns) and clonal evolution (12% versus 4%; P=ns) at 4 years was comparable between groups. Our results suggest that the outcome of immunosuppressive therapy with rabbit antithymocyte globulin is inferior to that of horse antithymocyte globulin. Although immunosuppressive therapy is an effective therapy in selected patients with refractory cytopenia of childhood, the long-term risk of relapse or clonal evolution remains. (ClinicalTrial.gov identifiers: NCT00662090).

Hematopoietic stem cell transplantation in children and young adults with secondary myelodysplastic syndrome and acute myelogenous leukemia after aplastic anemia.

Secondary myelodysplastic syndrome and acute myelogenous leukemia (sMDS/sAML) are the most serious secondary events occurring after immunosuppressive therapy in patients with aplastic anemia. Here we evaluate the outcome of hematopoietic stem cell transplantation (HSCT) in 17 children and young adults with sMDS/sAML after childhood aplastic anemia. The median interval between the diagnosis of aplastic anemia and the development of sMDS/sAML was 2.9 years (range, 1.2 to 13.0 years). At a median age of 13.1 years (range, 4.4 to 26.7 years), patients underwent HSCT with bone marrow (n = 6) or peripheral blood stem cell (n = 11) grafts from HLA-matched sibling donors (n = 2), mismatched family donors (n = 2), or unrelated donors (n = 13). Monosomy 7 was detected in 13 patients. The preparative regimen consisted of busulfan, cyclophosphamide, and melphalan in 11 patients and other agents in 6 patients. All patients achieved neutrophil engraftment. The cumulative incidence of grade II-IV acute graft-versus-host disease (GVHD) was 47%, and that of chronic GVHD was 70%. Relapse occurred in 1 patient. The major cause of death was transplant-related complication (n = 9). Overall survival and event-free survival at 5 years after HSCT were both 41%. In summary, this study indicates that HSCT is a curative therapy for some patients with sMDS/sAML after aplastic anemia. Future efforts should focus on reducing transplantation-related mortality.

Aberrant DNA methylation characterizes juvenile myelomonocytic leukemia with poor outcome.

Aberrant DNA methylation contributes to the malignant phenotype in virtually all types of cancer, including myeloid leukemia. We hypothesized that CpG island hypermethylation also occurs in juvenile myelomonocytic leukemia (JMML) and investigated whether it is associated with clinical, hematologic, or prognostic features. Based on quantitative measurements of DNA methylation in 127 JMML cases using mass spectrometry (MassARRAY), we identified 4 gene CpG islands with frequent hypermethylation: BMP4 (36% of patients), CALCA (54%), CDKN2B (22%), and RARB (13%). Hypermethylation was significantly associated with poor prognosis: when the methylation data were transformed into prognostic scores using a LASSO Cox regression model, the 5-year overall survival was 0.41 for patients in the top tertile of scores versus 0.72 in the lowest score tertile (P = .002). Among patients given allogeneic hematopoietic stem cell transplantation, the 5-year cumulative incidence of relapse was 0.52 in the highest versus 0.10 in the lowest score tertile (P = .007). In multivariate models, DNA methylation retained prognostic value independently of other clinical risk factors. Longitudinal analyses indicated that some cases acquired a more extensively methylated phenotype at relapse. In conclusion, our data suggest that a high-methylation phenotype characterizes an aggressive biologic variant of JMML and is an important molecular predictor of outcome.

Immunosuppressive therapy with anti-thymocyte globulin and cyclosporine A in selected children with hypoplastic refractory cytopenia.

It is currently unknown whether immunosuppressive therapy or hematopoietic stem cell transplantation is the most appropriate treatment strategy for children with refractory cytopenia and normal karyotype or trisomy 8. We report on 31 children with hypoplastic refractory cytopenia treated with immunosuppressive therapy consisting of antithymocyte globulin and cyclosporine. At 6 months, 22 of 29 evaluable patients had a complete or partial response; a total of ten patients achieved a complete response at varying time points. Six patients subsequently received a transplant because of non-response, progression to advanced myelodysplastic syndrome or evolution of monosomy 7. Overall and failure-free survival rates at 3 years were 88% and 57%, respectively.

Chimaerism analyses and subsequent immunological intervention after stem cell transplantation in patients with juvenile myelomonocytic leukaemia.

Chimaerism analysis was performed by polymerase chain reaction amplification of short-tandem repeat markers in 30 children following haematopoietic stem cell transplantation for juvenile myelomonocytic leukaemia (JMML). Fourteen patients always had complete chimaerism (CC); one of them relapsed after the discontinuation of the study and 13 continued in complete remission (CR). Mixed chimaerism (MC) was noted in 16 patients. Of those 12 patients demonstrated increasing MC (i-MC); 10 relapsed and two achieved CC following discontinuation of immunosuppressive therapy (IST). Four other patients demonstrating only transient MC are alive in CR. MC with up to 20% of autologous cells could be successfully eradicated without induction of severe graft-versus-host disease when IST was reduced or discontinued directly after the first demonstration of MC. At the same time, MC with up to 10% of autologous cells could disappear without intervention. The interval between MC and relapse ranged from 0-320 d (median 38 d). Donor leucocyte infusion was given to six patients with i-MC, but only one patient responded. Peripheral blood seems as valuable as bone marrow for chimaerism studies. In conclusion, serial quantitative chimaerism studies can identify patients with i-MC who are at high risk for relapse of JMML. Immediate withdrawal of IST is advised in these patients.

Hematopoietic stem cell transplantation (HSCT) in children with juvenile myelomonocytic leukemia (JMML): results of the EWOG-MDS/EBMT trial.

Allogeneic hematopoietic stem cell transplantation (HSCT) is the only proven curative therapy for juvenile myelomonocytic leukemia (JMML). We, the European Working Group on Childhood MDS (EWOG-MDS) and the European Blood and Marrow Transplantation (EBMT) Group, report the outcome of 100 children (67 boys and 33 girls) with JMML given unmanipulated HSCT after a preparative regimen including busulfan, cyclophosphamide, and melphalan. Forty-eight and 52 children received transplants from an HLA-identical relative or an unrelated donor (UD), respectively. The source of hematopoietic stem cells was bone marrow, peripheral blood, and cord blood in 79, 14, and 7 children, respectively. Splenectomy had been performed before HSCT in 24 children. The 5-year cumulative incidence of transplantation-related mortality and leukemia recurrence was 13% and 35%, respectively. Age older than 4 years predicted an increased risk of disease recurrence. The 5-year probability of event-free survival for children given HSCT from either a relative or a UD was 55% and 49%, respectively (P = NS), with median observation time of patients alive being 40 months (range, 6 to 144). In multivariate analysis, age older than 4 years and female sex predicted poorer outcome. Results of this study compare favorably with previously published reports. Disease recurrence remains the major cause of treatment failure. Outcome of UD-HSCT recipients is comparable to that of children receiving transplants from an HLA-identical sibling.

Refractory anemia in childhood: a retrospective analysis of 67 patients with particular reference to monosomy 7.

Primary myelodysplasia (MDS) without an increased number of blasts is a rare finding in childhood. We performed a retrospective analysis of 67 children with a diagnosis of primary MDS to determine the clinical and hematologic course of the disease. The median age at diagnosis was 8.3 years (range, 0.3-18.1 years). In contrast to refractory anemia in adults, 44% of patients had hemoglobin levels greater than 10 g/100 mL. The median white blood cell count and the absolute neutrophil count were 3.6 x 109/L and 0.9 x 109/L, respectively. Seventy-five percent of patients had thrombocytopenia. Bone marrow was hypocellular in 43% of the patients. Results of cytogenetic analysis showed monosomy 7 in 49%, trisomy 8 in 9%, and other abnormalities in 9% of the patients. The probability of survival 10 years after diagnosis was 0.48 (standard error [SE] = 0.10). Patients with monosomy 7 had significantly higher estimated probabilities of progression to advanced MDS than did patients with other chromosomal anomalies or normal karyotype. Of the 67 children, 41 underwent allogeneic stem cell transplantation (SCT). Patients whose disease did not progress to advanced MDS before SCT had significantly greater probability of survival than patients who experienced progression (0.76 [SE = 0.09] vs 0.36 [SE = 0.16]). SCT improved the outcomes for patients with monosomy 7 and should be offered early in the course of the disease. Recommendations for best treatment options for children with other chromosomal abnormalities or normal karyotype may have to await results of prospective clinical trials.