Allogeneic hematopoietic stem cell transplantation for 27 children with juvenile myelomonocytic leukemia diagnosed based on the criteria of the International JMML Working Group

Allogeneic hematopoietic cell transplantation in patients with juvenile myelomonocytic leukemia in Korea: a report of the Korean Pediatric Hematology-Oncology Group

Juvenile myelomonocytic leukemia (JMML) is a life-threatening myeloproliferative neoplasm. This multicenter study evaluated the characteristics, outcomes, and prognostic factors of allogeneic hematopoietic cell transplantation (HCT) in recipients with JMML who were diagnosed between 2000 and 2019 in Korea. Sixty-eight patients were retrospectively enrolled-28 patients (41.2%) received HCT during 2000-2010 and 40 patients (58.8%) during 2011-2020. The proportion of familial mismatched donors increased from 3.6 to 37.5%. The most common conditioning therapy was changed from Busulfan/Cyclophosphamide-based to Busulfan/Fludarabine-based therapy. The 5-year probabilities of event-free survival (EFS) and overall survival (OS) were 52.6% and 62.3%, respectively. The 5-year incidence of transplant-related mortality was 30.1%. Multivariate analysis revealed that the proportion of hemoglobin F ≥ 40%, abnormal cytogenetics, and matched sibling donors were independent risk factors for a higher relapse rate. Patients whose donor chimerism was below 99% had a significantly higher relapse rate. Better OS and lower treatment-related mortality were observed in patients with chronic graft-versus-host disease (GVHD), whereas grade III or IV acute GVHD was associated with worse EFS. In conclusion, the number of transplant increased along with the increase in alternative donor transplants, nevertheless, similar results were maintained. Alternative donor transplantation should be encouraged.

Targeted therapy in juvenile myelomonocytic leukemia: Where are we now?

Juvenile myelomonocytic leukemia (JMML) is a rare and aggressive clonal neoplasm of early childhood, classified as an overlap myeloproliferative/myelodysplastic neoplasm by the World Health Organization. In 90% of the patients with JMML, typical initiating mutations in the canonical Ras pathway genes NF1, PTPN11, NRAS, KRAS, and CBL can be identified. Hematopoietic stem cell transplantation (HSCT) currently is the established standard of care in most patients, although long-term survival is still only 50-60%. Given the limited therapeutic options and the important morbidity and mortality associated with HSCT, new therapeutic approaches are urgently needed. Hyperactivation of the Ras pathway as disease mechanism in JMML lends itself to the use of targeted therapy. Targeted therapy could play an important role in the future treatment of patients with JMML. This review presents a comprehensive overview of targeted therapies already developed and evaluated in vitro and in vivo in patients with JMML.

Hemophagocytic Lymphohistiocytosis Secondary to Juvenile Myelomonocytic Leukemia: A Case Report and Review of the Literature

RATIONALE

Juvenile myelomonocytic leukemia (JMML) is a rare hematopoietic disorder, which is more rarely accompanied by monosomy 5 or deletion of the long arm of chromosome 5q (-5/5q-) or monosomy 5 (5q-/-5), and hemophagocytic lymphohistiocytosis (HLH) is a rare, uncontrolled hyperinflammation condition, which is more rarely secondary to JMML. Up to now, only a few cases of JMML with -5/5q- and HLH secondary to JMML were described. Here we described an extremely rare case of HLH second to JMML with 5q-.

PATIENT CONCERNS

The patient had multiple cafe-au-lait-spots at birth and was found that NF1 gene mutation was positive. At his 6 years old, he developed hepatosplenomegaly, anemia, thrombocytopenia, monocyte count 4.12×109/L in peripheral blood, 13% blasts in peripheral blood, and 11% blasts in bone marrow, without BCR/ABL rearrangement, combining with positive NF1 gene mutation, he was diagnosed as JMML. In the bone marrow, there was chromosomal abnormalities with -5/5q-. In the treatment, HLH occurred.

DIAGNOSES

The patient was diagnosed as secondary HLH to JMML.

INTERVENTIONS

The patient received the chemotherapy treatment of the improved diffuse alveolar hemorrhage protocol, and meanwhile, he prepared for hematopoietic stem cell transplantation. Then on the basis of anti-infection, symptomatic and supportive therapy, he was commenced the treatment according to the HLH-2004 protocol.

OUTCOMES

He had a partial response, manifesting that his fever resolved, but the blood coagulation function did not improve, and the severe thrombocytopenia remained. Then, the parents refused the continual treatment, and the child died of intracranial hemorrhage 3 months after the diagnosis of JMML.

LESSONS

JMML and HLH were relatively easy to diagnose based on clinical and laboratory results. Due to the low incidence of JMML with -5/5q- and HLH secondary to JMML, no clinical practice guidelines for the treatment of the disease have been established yet. The clinical data of a case of HLH secondary to JMML with 5q- were analyzed, and relevant studies were studied.

Clinical outcome of cord blood transplantation for nine children with juvenile myelomonocytic leukemia receiving fludarabine-busulfan-cyclophosphamide-based conditioning

BACKGROUND

Juvenile myelomonocytic leukemia (JMML) is a rare hematological malignancy in young children and can only be cured through the allogeneic stem cell transplantation.

PROCEDURE

We have retrospectively analyzed the outcomes of nine children with JMML after unrelated cord blood transplantation (UCBT).

RESULTS

Eight patients who have received a myeloablative conditioning regimen of fludarabine (FLU), busulfan (BU), and cyclophosphamide (CY) have gotten engraftment. None of the nine patients has relapsed following initial UCBT. Six patients are still alive and in complete remission after UCBT with a median observation time of 43 months (range: 10-80 months).

CONCLUSIONS

This study shows that UCBT with FLU-BU-CY conditioning regimen can represent a suitable option for children with JMML.

A retrospective analysis of azacitidine treatment for juvenile myelomonocytic leukemia

Juvenile myelomonocytic leukemia (JMML) is a pediatric hematological malignancy with a poor prognosis. Although several case series have been published describing hematological and molecular responses to azacitidine (AZA) treatment in patients with JMML, the efficacy and safety profile of AZA is not well investigated, especially in Asian children and children undergoing hematopoietic stem cell transplantation (HSCT). We retrospectively analyzed 5 patients who received a total of 12 cycles (median 2 cycles) of AZA treatment in Japan. All five patients were boys and their ages at the time of treatment were 21, 23, 24, 26, and 46 months, respectively. All five patients tolerated AZA treatment, including four patients who received AZA after HSCT. Therapeutic toxicity with AZA was mostly limited to hematological toxicity. The only serious non-hematological adverse event was hyperbilirubinemia (grades III-IV) observed in a patient who received AZA after a second HSCT. Two out of five patients treated with AZA achieved a partial response (PR), while three patients treated for post-transplant relapse did not have an objective response. Future prospective studies should be conducted to develop combination therapies with AZA and other molecular targeted drugs for high-risk patients.

Donor Killer Immunoglobulin Receptor Gene Content and Ligand Matching and Outcomes of Pediatric Patients with Juvenile Myelomonocytic Leukemia Following Unrelated Donor Transplantation

Natural killer (NK) cell determinants predict relapse-free survival after allogeneic hematopoietic cell transplantation (HCT) for acute myelogenous leukemia, and previous studies have shown a beneficial graft-versus-leukemia effect in patients with juvenile myelomonocytic leukemia (JMML). However, whether NK cell determinants predict protection against relapse for JMML patients undergoing HCT is unknown. Therefore, we investigated NK cell-related donor and recipient immunogenetics as determinants of HCT outcomes in patients with JMML. Patients with JMML (age 0 to <19 years) who underwent a first allogeneic HCT from an unrelated donor between 2000 and 2017 and had available donor samples from the Center for International Blood and Marrow Transplant Research Repository were included. Donor killer immunoglobulin receptor (KIR) typing was performed on pre-HCT samples. The primary endpoint was disease-free survival (DFS); secondary endpoints included relapse, grade II-IV acute graft versus-host-disease (aGVHD), chronic GVHD (cGVHD), GVHD-free relapse-free survival, transplantation-related mortality, and overall survival (OS). Donor KIR models tested included KIR genotype (AA versus Bx), B content (0-1 versus ≥2), centromeric and telomeric region score (AA versus AB versus BB), B content score (best, better, or neutral), composite score (2 versus 3 versus 4), activating KIR content, and the presence of KIR2DS4. Ligand-ligand and KIR-ligand mismatch effects on outcomes were analyzed in HLA-mismatched donors (≤7/8; n = 74) only. Univariate analyses were performed for primary and secondary outcomes of interest, with a P value <.05 considered significant. One hundred sixty-five patients (113 males), with a median follow-up of 85 months (range, 6 to 216 months) met the study criteria. Of these, 111 underwent an unrelated donor HCT and 54 underwent a UCB HCT. Almost all (n = 161; 98%) received a myeloablative conditioning regimen. After exclusion of recipients of reduced-intensity/nonmyeloablative conditioning regimens and ex vivo T cell-depleted grafts (n = 8), there were 42 AA donors and 115 Bx donors, respectively. Three-year DFS, OS, relapse, and GRFS for the entire cohort were 58% (95% confidence interval [CI], 50% to 66%), 67% (95% CI, 59% to 74%), 26% (95% CI, 19% to 33%), and 27% (95% CI, 19% to 35%), respectively. The cumulative incidence of grade II-IV aGVHD at 100 days was 36% (95% CI, 27% to 44%), and that of cGVHD at 1 year was 23% (95% CI, 17% to 30%). There were no differences between AA donors and Bx donors for any recipient survival outcomes. The risk of grade II-IV aGVHD was lower in patients with donors with a B content score of ≥2 (hazard ratio [HR], 0.46; 95% CI, 0.26 to 0.83; P = .01), an activating KIR content score of >3 (HR, 0.52; 95% CI, 0.29 to 0.95; P = .032), centromeric A/B score (HR, 0.57; 95% CI, 033 to 0.98; P = .041), and telomeric A/B score (HR, 0.58; 95% CI, 0.34 to 1.00; P = .048). To our knowledge, this is the first study analyzing the association of NK cell determinants and outcomes in JMML HCT recipients. This study identifies potential benefits of donor KIR-B genotypes in reducing aGVHD. Our findings warrant further study of the role of NK cells in enhancing the graft-versus-leukemia effect via recognition of JMML blasts.

Current Treatment of Juvenile Myelomonocytic Leukemia

Juvenile myelomonocytic leukemia (JMML) is a rare pediatric leukemia characterized by mutations in five canonical RAS pathway genes. The diagnosis is made by typical clinical and hematological findings associated with a compatible mutation. Although this is sufficient for clinical decision-making in most JMML cases, more in-depth analysis can include DNA methylation class and panel sequencing analysis for secondary mutations. NRAS-initiated JMML is heterogeneous and adequate management ranges from watchful waiting to allogeneic hematopoietic stem cell transplantation (HSCT). Upfront azacitidine in KRAS patients can achieve long-term remissions without HSCT; if HSCT is required, a less toxic preparative regimen is recommended. Germline CBL patients often experience spontaneous resolution of the leukemia or exhibit stable mixed chimerism after HSCT. JMML driven by PTPN11 or NF1 is often rapidly progressive, requires swift HSCT and may benefit from pretransplant therapy with azacitidine. Because graft-versus-leukemia alloimmunity is central to cure high risk patients, the immunosuppressive regimen should be discontinued early after HSCT.

Pediatric Neoplasms Presenting with Monocytosis

PURPOSE OF REVIEW

Juvenile myelomonocytic leukemia (JMML) is a rare but severe pediatric neoplasm with hematopoietic stem cell transplant as its only established curative option. The development of targeted therapeutics for JMML is being guided by an understanding of the pathobiology of this condition. Here, we review JMML with an emphasis on genetics in order to (i) demonstrate the relationship between JMML genotype and clinical phenotype and (ii) explore potential genetic targets of novel JMML therapies.

RECENT FINDINGS

DNA hypermethylation studies have demonstrated consistently that methylation is related to disease severity. Increasing understanding of methylation in JMML may open the door to novel therapies, such as DNA methyltransferase inhibitors. The PI3K/AKT/MTOR, JAK/STAT, and RAF/MEK/ERK pathways are being investigated as therapeutic targets for JMML. Future therapy for JMML will be driven by an increased understanding of pathobiology. Targeted therapeutic approaches hold potential for improving outcomes in patients with JMML.

Combination of DNA-hypomethylating agent and hematopoietic stem cell transplantation in treatment of juvenile myelomonocytic leukemia: A case report

INTRODUCTION

Juvenile myelomonocytic leukemia (JMML) is a rare myeloproliferative neoplasm of early childhood characterized by excessive proliferation of myelomonocytic cells and an aggressive clinical course. Allogenic hematopoietic stem cell transplantation (HSCT) is a firmly established treatment, but patients without fully matched donors have poor prognoses. Disease recurrence is the main cause of treatment failure. Meanwhile, most cases with splenomegaly present with platelet transfusion refractoriness, but splenectomy remains controversial. DNA hypermethylation correlates with poor prognosis in JMML; however, hypomethylating therapy alone does not eradicate leukemic clones. Thus, a suitable treatment with a good success rate remains elusive.

PATIENT CONCERNS

Here, we report our experience with a patient who suffered from recurrent fever, pallor, abdominal distention, leukocytosis, and thrombocytopenia with a silent past history and family history of somatic KRAS mutation. The patient was treated with decitabine as a bridging therapy before haploidentical HSCT. Decitabine was also used prophylactically after transplantation.

DIAGNOSIS

We arrived at a JMML diagnosis after observing leukocytosis, less than 20% blast cells in the peripheral blood and bone marrow, increased monocyte counts, negativity for the BCR-ABL fusion gene, positivity for somatic KRAS mutation, and massive splenomegaly.

INTERVENTIONS

The patient accepted splenectomy before HSCT, and haploidentical HSCT was applied after treatment with a DNA-hypomethylating agent. The hypomethylating agent was administered for 1 year after HSCT to prevent disease recurrence.

OUTCOMES

The patient presented with complete remission of the disease and mild graft versus host disease for 26 months after treatment with decitabine and HSCT.

LESSONS

Combining haploidentical HSCT and DNA-hypomethylating agents may improve the prognosis of JMML. Meanwhile, splenectomy could be an effective option in cases with massive splenomegaly and platelet transfusion refractoriness.

Allogeneic hematopoietic stem cell transplant in rare hematologic disorders: a single center experience from Pakistan

Management of rare hematological disorders pose unique diagnostic and therapeutic challenges due to unusual occurrence and limited treatment options. We retrospectively identified 45 patients receiving matched related donor transplant for rare hematological disorders from 2006 to 2019. Patients were divided into two groups (1) malignant and (2) non malignant. The malignant disorder group included four patients while the nonmalignant group included 41 patients divided into immune dysregulation (n = 23), bone marrow failure (n = 10), metabolic (n = 5), and bleeding diathesis (n = 3). Twenty-six (57.8%) patients received myeloablative conditioning (MAC) and 16 (35.6%) received reduced intensity conditioning (RIC), while 3 (6.6%) patients with severe combined immunodeficiency received stem cell infusion alone without conditioning. The cumulative incidence (CI) of grade II-IV acute GVHD (aGVHD) was 39.1% (n = 18) and chronic GVHD (cGVHD) 15.2% (n = 7). There was no primary graft failure while CI of secondary graft failure was 9%. Overall survival (OS) and disease-free survival (DFS) was 82.2% and 77.8% respectively. Group wise OS was 75% in the malignant group, 82.6% in the immune dysregulation group, 80% in patients with metabolic disorders and bone marrow failure, while 100% in patients with bleeding diathesis. This retrospective analysis shows that hematopoietic stem cell transplant can be a feasible treatment option for rare hematological disorders.

Clinical Outcomes after Allogeneic Hematopoietic Stem Cell Transplantation in Children with Juvenile Myelomonocytic Leukemia: A Report from the Japan Society for Hematopoietic Cell Transplantation

Hematopoietic stem cell transplantation (HSCT) is the only curative treatment for juvenile myelomonocytic leukemia (JMML), but few large studies of HSCT for JMML exist. Using data from the Japan Society for Hematopoietic Cell Transplantation registry, we analyzed the outcomes of 129 children with JMML who underwent HSCT between 2000 and 2011. The 5-year overall survival (OS) rate and cumulative incidence of relapse were 64% and 34%, respectively. A regimen of busulfan/fludarabine/melphalan was the most commonly used (59 patients) and provided the best outcomes; the 5-year OS rate reached 73%, and the cumulative incidences of relapse and transplantation-related mortality were 26% and 9%, respectively. In contrast, the use of the irradiation-based myeloablative regimen was the most significant risk factor for OS (hazard ratio [HR], 2.92; P = .004) in the multivariate model. In addition, chronic graft-versus-host disease (GVHD) was strongly associated with lower relapse (HR, 0.37; P = .029) and favorable survival (HR, 0.22; P = .006). The current study has shown that a significant proportion of children with JMML can be cured with HSCT, especially those receiving the busulfan/fludarabine/melphalan regimen. Based on the lower relapse and better survival observed in patients with chronic GVHD, additional treatment strategies that focus on enhancing graft-versus-leukemia effects may further improve survival.

Molecular assessment of pretransplant chemotherapy in the treatment of juvenile myelomonocytic leukemia

BACKGROUND

Despite the intensity of hematopoietic stem cell transplantation (HCT), relapse remains the most common cause of death in juvenile myelomonocytic leukemia (JMML). In contrast to other leukemias where therapy is used to reduce leukemic burden prior to transplant, many patients with JMML proceed directly to HCT with active disease. The objective of this study was to elucidate whether pre-HCT therapy has an effect on the molecular burden of disease and how this affects outcome post-HCT.

PROCEDURE

Twenty-one patients with JMML who received pre-HCT therapy and were transplanted at UCSF were analyzed in this study. The mutant allele frequency of the driver mutation was assessed before and after pre-HCT therapy, using custom amplicon next-generation sequencing.

RESULTS

Of the 21 patients, seven patients (33%) responded to therapy with a significant reduction in their mutant allele frequency and were classified as molecular responders. Six of these patients received moderate-intensity chemotherapy, one patient received only azacitidine. The 5-year progression-free survival after HCT of molecular responders was 100% versus 61% for nonresponders (P = .12). Survival of molecular nonresponders was not improved by use of high-intensity conditioning, but patients were salvaged if they experienced severe graft versus host disease. There were no baseline clinical characteristics that were associated with response to pre-HCT therapy.

CONCLUSIONS

Despite the myelodysplastic nature of JMML, patients treated with pre-HCT therapy can achieve molecular remissions. These patients experienced a trend toward improved outcomes post-HCT. Importantly, molecular testing can be helpful to distinguish between responders and nonresponders and should become an integral part of clinical care.

Successful hematopoietic stem cell transplantation from an HLA-mismatched parent for engraftment failure after unrelated cord blood transplantation in patients with juvenile myelomonocytic leukemia: Report of two cases

JMML is an aggressive hematopoietic malignancy of early childhood, and allogeneic HSCT is the only curative treatment for this disease. Umbilical cord blood is one of donor sources for HSCT in JMML patients who do not have an HLA-compatible relative, but engraftment failure remains a major problem. Here, we report two cases of JMML who were successfully rescued by HSCT from an HLA-mismatched parent after development of primary engraftment failure following unrelated CBT. Both patients had severe splenomegaly and underwent unrelated CBT from an HLA-mismatched donor. Immediately after diagnosis of engraftment failure, both patients underwent HSCT from their parent. For the second HSCT, we used RIC regimens consisting of FLU, CY, and a low dose of rabbit ATG with or without TBI and additionally administered ETP considering their persistent severe splenomegaly. Both patients achieved engraftment without severe treatment-related adverse effects. After engraftment of second HSCT, their splenomegaly was rapidly regressed, and both patients showed no sign of relapse for over 4 years. These observations demonstrate that HSCT from an HLA-mismatched parent could be a feasible salvage treatment for primary engraftment failure in JMML patients.

DNA-hypomethylating agents as epigenetic therapy before and after allogeneic hematopoietic stem cell transplantation in myelodysplastic syndromes and juvenile myelomonocytic leukemia

Myelodysplastic syndrome (MDS) is a clonal bone marrow disorder, typically of older adults, which is characterized by ineffective hematopoiesis, peripheral blood cytopenias and risk of progression to acute myeloid leukemia. Juvenile myelomonocytic leukemia (JMML) is an aggressive myeloproliferative neoplasm occurring in young children. The common denominator of these malignant myeloid disorders is the limited benefit of conventional chemotherapy and a particular responsiveness to epigenetic therapy with the DNA-hypomethylating agents 5-azacytidine (azacitidine) or decitabine. However, hypomethylating therapy does not eradicate the malignant clone in MDS or JMML and allogeneic hematopoietic stem cell transplantation (HSCT) remains the only curative treatment option. An emerging concept with intriguing potential is the combination of hypomethylating therapy and HSCT. Possible advantages include disease control with good tolerability during donor search and HSCT preparation, improved antitumoral alloimmunity, and reduced risk of relapse even with non-myeloablative regimens. Herein we review the current role of pre- and post-transplant therapy with hypomethylating agents in MDS and JMML.

Association Between Juvenile Myelomonocytic Leukemia, Juvenile Xanthogranulomas and Neurofibromatosis Type 1: Case Report and Review of the Literature

The occurrence of juvenile myelomonocytic leukemia (JMML), juvenile xanthogranuloma (JXG), and neurofibromatosis type 1 (NF1) together is relatively rare. Approximately only 20 cases have been reported in the literature. It is debated whether children with NF1 and JXG are at higher risk of developing JMML than children with NF1 alone. We present the case of a boy primarily diagnosed with NF1 with coexisting JXG who developed JMML at the age of 22 months. The clinical course from initial presentation to final diagnosis is detailed and the genetic features and hematologic characteristics are discussed. We report this case to underscore the importance of close monitoring of blood count and strict clinical follow-up in children presenting with concurrent NF1 and JXG and provide a possible explanation for this association.

Juvenile Myelomonocytic Leukemia in Turkey: A Retrospective Analysis of Sixty-five Patients

OBJECTIVE

This study aimed to define the status of juvenile myelomonocytic leukemia (JMML) patients in Turkey in terms of time of diagnosis, clinical characteristics, mutational studies, clinical course, and treatment strategies.

MATERIALS AND METHODS

Data including clinical and laboratory characteristics and treatment strategies of JMML patients were collected retrospectively from pediatric hematology-oncology centers in Turkey.

RESULTS

Sixty-five children with JMML diagnosed between 2002 and 2016 in 18 institutions throughout Turkey were enrolled in the study. The median age at diagnosis was 17 months (min-max: 2-117 months). Splenomegaly was present in 92% of patients at the time of diagnosis. The median white blood cell, monocyte, and platelet counts were 32.9x109/L, 5.4x109/L, and 58.3x109/L, respectively. Monosomy 7 was present in 18% of patients. JMML mutational analysis was performed in 32 of 65 patients (49%) and PTPN11 was the most common mutation. Hematopoietic stem cell transplantation (HSCT) could only be performed in 28 patients (44%), the majority being after the year 2012. The most frequent reason for not performing HSCT was the inability to find a suitable donor. The median time from diagnosis to HSCT was 9 months (min-max: 2-63 months). The 5-year cumulative survival rate was 33% and median estimated survival time was 30±17.4 months (95% CI: 0-64.1) for all patients. Survival time was significantly better in the HSCT group (log-rank p=0.019). Older age at diagnosis (>2 years), platelet count of less than 40x109/L, and PTPN11 mutation were the factors significantly associated with shorter survival time.

CONCLUSION

Although there has recently been improvement in terms of definitive diagnosis and HSCT in JMML patients, the overall results are not satisfactory and it is necessary to put more effort into this issue in Turkey.

Diagnosis and treatment of juvenile myelomonocytic leukemia

Juvenile myelomonocytic leukemia (JMML) is a rare myelodysplastic/myeloproliferative disorder that occurs during infancy and early childhood; this disorder is characterized by hypersensitivity of the myeloid progenitor cells to granulocyte-macrophage colony-stimulating factor in vitro. JMML usually involves somatic and/or germline mutations in the genes of the RAS pathway, including PTPN11, NRAS, KRAS, NF1, and CBL, in the leukemic cells. Almost all patients with JMML experience an aggressive clinical course, and hematopoietic stem cell transplantation (HSCT) is the only curative treatment. A certain proportion of patients with somatic NRAS and germline mutations in CBL, however, have spontaneous resolution. A suitable treatment after diagnosis and conditioning regimen prior to HSCT are yet to be determined, but several clinical trials have been initiated throughout the world to develop suitable pre- or post-allogeneic HSCT treatments and new targeted therapies that are less toxic, to improve patient outcome.

RAS diseases in children

RAS genes encode a family of 21 kDa proteins that are an essential hub for a number of survival, proliferation, differentiation and senescence pathways. Signaling of the RAS-GTPases through the RAF-MEK-ERK pathway, the first identified mitogen-associated protein kinase (MAPK) cascade is essential in development. A group of genetic syndromes, named "RASopathies", had been identified which are caused by heterozygosity for germline mutations in genes that encode protein components of the RAS/MAPK pathway. Several of these clinically overlapping disorders, including Noonan syndrome, Noonan-like CBL syndrome, Costello syndrome, cardio-facio-cutaneous (CFC) syndrome, neurofibromatosis type I, and Legius syndrome, predispose to cancer and abnormal myelopoiesis in infancy. This review focuses on juvenile myelomonocytic leukemia (JMML), a malignancy of early childhood characterized by initiating germline and/or somatic mutations in five genes of the RAS/MAPK pathway: PTPN11, CBL, NF-1, KRAS and NRAS. Natural courses of these five subtypes differ, although hematopoietic stem cell transplantation remains the only curative therapy option for most children with JMML. With whole-exome sequencing studies revealing few secondary lesions it will be crucial to better understand the RAS/MAPK signaling network with its crosstalks and feed-back loops to carefully design early clinical trials with novel pharmacological agents in this still puzzling leukemia.

Phase II/III trial of a pre-transplant farnesyl transferase inhibitor in juvenile myelomonocytic leukemia: a report from the Children's Oncology Group

BACKGROUND

Juvenile myelomonocytic leukemia (JMML) is not durably responsive to chemotherapy, and approximately 50% of patients relapse after hematopoietic stem cell transplant (HSCT). Here we report the activity and acute toxicity of the farnesyl transferase inhibitor tipifarnib, the response rate to 13-cis retinoic acid (CRA) in combination with cytoreductive chemotherapy, and survival following HSCT in children with JMML.

PROCEDURE

Eighty-five patients with newly diagnosed JMML were enrolled on AAML0122 between 2001 and 2006. Forty-seven consented to receive tipifarnib in a phase II window before proceeding to a phase III trial of CRA in combination with fludarabine and cytarabine followed by HSCT and maintenance CRA. Thirty-eight patients enrolled only in the phase III trial.

RESULTS

Overall response rate was 51% after tipifarnib and 68% after fludarabine/cytarabine/CRA. Tipifarnib did not increase pre-transplant toxicities. Forty-six percent of the 44 patients who received protocol compliant HSCT relapsed. Five-year overall survival was 55 ± 11% and event-free survival was 41 ± 11%, with no significant difference between patients who did or did not receive tipifarnib.

CONCLUSIONS

Administration of tipifarnib in the window setting followed by HSCT in patients with newly diagnosed JMML was safe and yielded a 51% initial response rate as a single agent, but failed to reduce relapse rates or improve long-term overall survival.

How I treat juvenile myelomonocytic leukemia

Juvenile myelomonocytic leukemia (JMML) is a unique, aggressive hematopoietic disorder of infancy/early childhood caused by excessive proliferation of cells of monocytic and granulocytic lineages. Approximately 90% of patients carry either somatic or germline mutations of PTPN-11, K-RAS, N-RAS, CBL, or NF1 in their leukemic cells. These genetic aberrations are largely mutually exclusive and activate the Ras/mitogen-activated protein kinase pathway. Allogeneic hematopoietic stem cell transplantation (HSCT) remains the therapy of choice for most patients with JMML, curing more than 50% of affected children. We recommend that this option be promptly offered to any child with PTPN-11-, K-RAS-, or NF1-mutated JMML and to the majority of those with N-RAS mutations. Because children with CBL mutations and few of those with N-RAS mutations may have spontaneous resolution of hematologic abnormalities, the decision to proceed to transplantation in these patients must be weighed carefully. Disease recurrence remains the main cause of treatment failure after HSCT. A second allograft is recommended if overt JMML relapse occurs after transplantation. Recently, azacytidine, a hypomethylating agent, was reported to induce hematologic/molecular remissions in some children with JMML, and its role in both reducing leukemia burden before HSCT and in nontransplant settings requires further studies.

Transplantation for juvenile myelomonocytic leukemia: a retrospective study of 30 children treated with a regimen of busulfan, fludarabine, and melphalan

We report the outcomes of 30 patients with juvenile myelomonocytic leukemia (JMML) who received unmanipulated hematopoietic stem cell transplantation (HSCT) with oral or intravenous busulfan, fludarabine, and melphalan between 2001 and 2011. Mutations in PTPN11 were detected in 15 patients. Six patients received human leukocyte antigen (HLA)-matched HSCT from related donors, and 24 patients received HSCT from alternative donors, including 13 HLA-mismatched donors. Primary engraftment failed in five patients, all of whom had received allografts from HLA-mismatched donors. HLA-mismatched HSCT resulted in poorer event-free survival than HLA-matched HSCT (28.8 vs. 70.6 %). Three patients died of transplantation-related causes, and eight patients experienced hematological relapse (including five patients who died due to disease progression). Eight patients received a second HSCT, and four of these patients have survived. The 5-year estimated overall survival for all patients was 72.4: 88.9 % for the patients without a mutation in PTPN11 (n = 10) and 58.3 % for the patients with a mutation in PTPN11 (n = 15) (P = 0.092). The conditioning regimen reported in the present study achieved hematological and clinical remission in >50 % of patients with JMML who received HSCT from alternative donors, and may also be effective for JMML patients with PTPN11 mutation.

Juvenile myelomonocytic leukemia in India: cure remains a distant dream!

There is paucity of outcome data regarding juvenile myelomonocytic leukemia from India. We report a series of eight children. Three had monosomy 7 and one had complex cytogenetics. One with Down's syndrome recovered spontaneously. Three refused therapy of whom only one is alive with disease. One died post chemotherapy. Three underwent allogeneic stem cell transplant after protracted delay with funds arranged from various governmental and non-governmental organizations. Of these two died (relapse-1 and intracranial bleed-1) and one is alive and disease free. In India, it's a milestone to reach transplant due to high cost and cure still remains a distant dream.

Bedside to bench in juvenile myelomonocytic leukemia: insights into leukemogenesis from a rare pediatric leukemia

Juvenile myelomonocytic leukemia (JMML) is a typically aggressive myeloid neoplasm of childhood that is clinically characterized by overproduction of monocytic cells that can infiltrate organs, including the spleen, liver, gastrointestinal tract, and lung. JMML is categorized as an overlap myelodysplastic syndrome/myeloproliferative neoplasm (MDS/MPN) by the World Health Organization and also shares some clinical and molecular features with chronic myelomonocytic leukemia, a similar disease in adults. Although the current standard of care for patients with JMML relies on allogeneic hematopoietic stem cell transplant, relapse is the most frequent cause of treatment failure. Tremendous progress has been made in defining the genomic landscape of JMML. Insights from cancer predisposition syndromes have led to the discovery of nearly 90% of driver mutations in JMML, all of which thus far converge on the Ras signaling pathway. This has improved our ability to accurately diagnose patients, develop molecular markers to measure disease burden, and choose therapeutic agents to test in clinical trials. This review emphasizes recent advances in the field, including mapping of the genomic and epigenome landscape, insights from new and existing disease models, targeted therapeutics, and future directions.

Analysis of risk factors influencing outcomes after cord blood transplantation in children with juvenile myelomonocytic leukemia: a EUROCORD, EBMT, EWOG-MDS, CIBMTR study

We retrospectively analyzed 110 patients with juvenile myelomonocytic leukemia, given single-unit, unrelated donor umbilical cord blood transplantation. Median age at diagnosis and at transplantation was 1.4 years (age range, 0.1-6.4 years) and 2.2 years (age range, 0.5-7.4 years), respectively. Before transplantation, 88 patients received chemotherapy; splenectomy was performed in 24 patients. Monosomy of chromosome 7 was the most frequent cytogenetic abnormality, found in 24% of patients. All but 8 patients received myeloablative conditioning; cyclosporine plus steroids was the most common graft-versus-host disease prophylaxis. Sixteen percent of units were HLA-matched with the recipient, whereas 43% and 35% had either 1 or 2 to 3 HLA disparities, respectively. The median number of nucleated cells infused was 7.1 × 10(7)/kg (range, 1.7-27.6 × 10(7)/kg). With a median follow-up of 64 months (range, 14-174 months), the 5-year cumulative incidences of transplantation-related mortality and relapse were 22% and 33%, respectively. The 5-year disease-free survival rate was 44%. In multivariate analysis, factors predicting better disease-free survival were age younger than 1.4 years at diagnosis (hazard ratio [HR], 0.42; P = .005), 0 to 1 HLA disparities in the donor/recipient pair (HR, 0.4; P = .009), and karyotype other than monosomy 7 (HR, 0.5; P = .02). Umbilical cord blood transplantation may cure a relevant proportion of children with juvenile myelomonocytic leukemia. Because disease recurrence remains the major cause of treatment failure, strategies to reduce incidence of relapse are warranted.

Outcomes of immunological interventions for mixed chimerism following allogeneic stem cell transplantation in children with juvenile myelomonocytic leukemia

BACKGROUND

For children with juvenile myelomonocytic leukemia (JMML) who undergo stem cell transplantation (SCT), the role of immunological interventions including withdrawal of immunosuppressive therapy (IST) and donor lymphocyte infusion (DLI) for treatment of disease recurrence remains uncertain.

PROCEDURE

We analyzed serial chimerism status following SCT and evaluated the efficacy of immunological interventions for the management of mixed chimerism (MC) in children with JMML.

RESULTS

Chimerism analysis was available in 26 SCT cases following the first and second SCT. MC was observed in 16 cases and withdrawal of IST was performed in 14 cases immediately after identification of MC. Donor lymphocyte infusion (DLI) was performed in five MC cases. Eight MC cases were observed at the time of neutrophil recovery. Following withdrawal of IST, three cases achieved complete chimerism (CC) while the proportion of autologous cells increased rapidly in the remaining five cases. Six MC cases were observed after achievement of hematological remission (HR) and responses to withdrawal of IST were observed in two cases. In the remaining four cases, despite withdrawal of IST, the proportion of autologous cells increased. Five cases received DLI but only one case responded.

CONCLUSION

Although the benefits of immunological interventions for MC after SCT in JMML were limited, some patients did achieve HR as a result of these treatment modalities without a second SCT. Close monitoring of donor chimerism and early detection of MC is helpful in guiding treatment after SCT in children with JMML.

Current management of juvenile myelomonocytic leukemia and the impact of RAS mutations

Juvenile myelomonocytic leukemia (JMML) is a rare clonal myelodysplastic/myeloproliferative disorder that affects young children. It is characterized by hypersensitivity of JMML cells to granulocyte-macrophage colony-stimulating factor (GM-CSF) in vitro. The pathogenesis of JMML seems to arise from constitutional activation of the GM-CSF/RAS (a GTPase) signaling pathway, a result of mutations in RAS, NF1, PTPN11, and CBL that interfere with downstream components of the pathway. Most patients with JMML usually experience an aggressive clinical course, and hematopoietic stem cell transplantation (HSCT) is currently the only curative treatment, although the high rates of relapses and graft failures are of great concern. In contrast, a certain proportion of patients experience a stable clinical course for a considerable period of time, and sometimes the disease even spontaneously resolves without any treatment. Recent studies have provided us with increased knowledge of genotype-phenotype correlations in JMML, and suggested that differences in clinical courses may reflect genetic status. Thus, genotype-based management is of current international interest, especially for JMML with RAS mutations. Cumulative evidence suggests that RAS mutations can be related to favorable clinical outcomes, and HSCT may not have to be a mandatory therapeutic option for a portion of patients with this mutation, although a consensus regarding genotype-based management has not yet been achieved. Further efforts toward identifying which patients who will do well without HSCT are required.

Molecular targets for the treatment of juvenile myelomonocytic leukemia

Significant advances in our understanding of the genetic defects and the pathogenesis of juvenile myelomonocytic leukemia (JMML) have been achieved in the last several years. The information gathered tremendously helps us in designing molecular targeted therapies for this otherwise fatal disease. Various approaches are being investigated to target defective pathways/molecules in this disease. However, effective therapy is still lacking. Development of specific target-based drugs for JMML remains a big challenge and represents a promising direction in this field.

Recent advances in the pathogenesis and treatment of juvenile myelomonocytic leukaemia

Myeloid neoplasms derive from the pathological clonal expansion of an abnormal stem cell and span a diverse spectrum of phenotypes including acute myeloid leukaemia (AML), myeloproliferative neoplasms (MPN) and myelodysplastic syndromes (MDS). Expansion of myeloid blasts with suppression of normal haematopoiesis is the hallmark of AML, whereas MPN is associated with over-proliferation of one or more lineages that retain the capacity to differentiate, and MDS is characterized by cytopenias and aberrant differentiation. MPD and MDS can progress to AML, which is likely due to the acquisition of cooperative mutations. Juvenile myelomonocytic leukaemia (JMML) is an aggressive myeloid neoplasm of childhood that is clinically characterized by overproduction of monocytic cells that can infiltrate organs, including the spleen, liver, gastrointestinal tract, and lung. JMML is categorized as an overlap MPN/MDS by the World Health Organization and also shares some clinical and molecular features with chronic myelomonocytic leukaemia, a similar disease in adults. While the current standard of care for patients with JMML relies on allogeneic haematopoietic stem cell transplant (HSCT), relapse is the most frequent cause of treatment failure. This review outlines our understanding of the genetic underpinnings of JMML with a recent update on the discovery of novel CBL mutations, as well as a brief review on current therapeutic approaches.

Gene expression-based classification as an independent predictor of clinical outcome in juvenile myelomonocytic leukemia

PURPOSE Juvenile myelomonocytic leukemia (JMML) is a rare early childhood myelodysplastic/myeloproliferative disorder characterized by an aggressive clinical course. Age and hemoglobin F percentage at diagnosis have been reported to predict both survival and outcome after hematopoietic stem cell transplantation (HSCT). However, no genetic markers with prognostic relevance have been identified so far. We applied gene expression-based classification to JMML samples in order to identify prognostic categories related to clinical outcome. PATIENTS AND METHODS Samples of 44 patients with JMML were available for microarray gene expression analysis. A diagnostic classification (DC) model developed for leukemia and myelodysplastic syndrome classification was used to classify the specimens and identify prognostically relevant categories. Statistical analysis was performed to determine the prognostic value of the classification and the genes identifying prognostic categories were further analyzed through R software. RESULTS The samples could be divided into two major groups: 20 specimens were classified as acute myeloid leukemia (AML) -like and 20 samples as nonAML-like. Four patients could not be assigned to a unique class. The 10-year probability of survival after diagnosis of AML-like and nonAML-like patients was significantly different (7% v 74%; P = .0005). Similarly, the 10-year event-free survival after HSCT was 6% for AML-like and 63% for nonAML-like patients (P = .0010). CONCLUSION Gene expression-based classification identifies two groups of patients with JMML with distinct prognosis outperforming all known clinical parameters in terms of prognostic relevance. Gene expression-based classification could thus be prospectively used to guide clinical/therapeutic decisions.

Juvenile myelomonocytic leukemia: epidemiology, etiopathogenesis, diagnosis, and management considerations

Juvenile myelomonocytic leukemia (JMML) is a rare hematopoietic malignancy of early childhood with features characteristic of both myelodysplastic and myeloproliferative disorders. Recent studies clearly show that the deregulated activation of the RAS signaling pathway plays a central role in the pathogenesis of JMML. Somatic defects in either RAS, PTPN11 or NF1 genes involved in this pathway are detected in 70-80% of JMML patients, allowing a molecular diagnosis to be made in the majority of cases. Patients with JMML respond poorly to chemotherapy, and the probability of survival without allogeneic hematopoietic stem cell transplantation (HSCT) is less than 10%. Recent studies show that the event-free survival after HSCT is between 24 and 54%, with no difference between transplants using matched family donors and those using unrelated donors. The use of therapies such as intensive chemotherapy and splenectomy prior to HSCT does not improve the outcome. The relapse rate following HSCT is over 30%, which is unacceptably high. Cumulative evidence suggests that a graft-versus-leukemia effect occurs in JMML. Donor leukocyte infusion is not usually successful in JMML, but the outcome of second HSCT is generally favorable. Based on recent advances in the understanding of the pathogenesis of JMML, the development of novel targeted therapies, which might improve the outcome of patients, is keenly awaited.

Childhood myelodysplastic syndrome: focus on the approach to diagnosis and treatment of juvenile myelomonocytic leukemia

Expansion of myeloid blasts with suppression of normal hematopoiesis is a hallmark of acute myeloid leukemia (AML). In contrast, myeloproliferative neoplasms (MPNs) are clonal disorders characterized by overproliferation of one or more lineages that retain the ability to differentiate. Juvenile myelomonocytic leukemia (JMML) is an aggressive MPN of childhood that is clinically characterized by the overproduction of monocytic cells that can infiltrate organs, including the spleen, liver, gastrointestinal tract, and lung. Major progress in understanding the pathogenesis of JMML has been achieved by mapping out the genetic lesions that occur in patients. The spectrum of mutations described thus far in JMML occur in genes that encode proteins that signal through the Ras/mitogen-activated protein kinase (MAPK) pathways, thus providing potential new opportunities for both diagnosis and therapy. These genes include NF1, NRAS, KRAS, PTPN11, and, most recently, CBL. While the current standard of care for patients with JMML relies on allogeneic hematopoietic stem-cell transplant, relapse is the most frequent cause of treatment failure. Rarely, spontaneous resolution of this disorder can occur but is unpredictable. This review is focused on the genetic abnormalities that occur in JMML, with particular attention to germ-line predisposition syndromes associated with the disorder. Current approaches to therapy are also discussed.

Mutations of an E3 ubiquitin ligase c-Cbl but not TET2 mutations are pathogenic in juvenile myelomonocytic leukemia

Juvenile myelomonocytic leukemia (JMML) is a rare pediatric myeloid neoplasm characterized by excessive proliferation of myelomonocytic cells. When we investigated the presence of recurrent molecular lesions in a cohort of 49 children with JMML, neurofibromatosis phenotype (and thereby NF1 mutation) was present in 2 patients (4%), whereas previously described PTPN11, NRAS, and KRAS mutations were found in 53%, 4%, and 2% of cases, respectively. Consequently, a significant proportion of JMML patients without identifiable pathogenesis prompted our search for other molecular defects. When we applied single nucleotide polymorphism arrays to JMML patients, somatic uniparental disomy 11q was detected in 4 of 49 patients; all of these cases harbored RING finger domain c-Cbl mutations. In total, c-Cbl mutations were detected in 5 (10%) of 49 patients. No mutations were identified in Cbl-b and TET2. c-Cbl and RAS pathway mutations were mutually exclusive. Comparison of clinical phenotypes showed earlier presentation and lower hemoglobin F levels in patients with c-Cbl mutations. Our results indicate that mutations in c-Cbl may represent key molecular lesions in JMML patients without RAS/PTPN11 lesions, suggesting analogous pathogenesis to those observed in chronic myelomonocytic leukemia (CMML) patients.

Juvenile myelomonocytic leukemia: report of seven cases and review of literature

Juvenile myelomonocytic leukemia (JMML) is a rare, aggressive, clonal hematopoietic disorder of childhood with features of both myelodysplasia (thrombocytopenia, anemia) and myeloproliferation (leukocytosis, monocytosis). In most cases there is marrow hypercellularity, splenomegaly, and extramedullary involvement. In 1997 an international consensus on terminology was reached and guidelines/criteria for diagnosis were proposed. A recent World Health Organization classification described the current diagnostic criteria of JMML. Although the diagnosis of JMML has been facilitated, it can be challenging, especially in the early stages or when it 1st presents as an extramedullary tumor. We report a series of 7 cases diagnosed over a period of 10 years (from January 1, 1996, to December 31, 2005). Two cases had interesting associated findings that would potentially lead to delay in diagnosis or misdiagnosis. Two other cases had extramedullary involvement with symptoms referable to the organs of involvement at presentation. Clinical and pathologic findings are summarized with a review of relevant literature.

Correlation of clinical features with the mutational status of GM-CSF signaling pathway-related genes in juvenile myelomonocytic leukemia

Mutations in RAS, neurofibromatosis type 1 (NF1), and PTPN11, constituents of the granulocyte-macrophage colony-stimulating factor signaling pathway, have been recognized in patients with juvenile myelomonocytic leukemia (JMML). We assessed 71 children with JMML for NRAS, KRAS, and PTPN11 mutations and evaluated their clinical significance. Of the 71 patients, three had been clinically diagnosed with neurofibromatosis type 1, and PTPN11 and NRAS/KRAS mutations were found in 32 (45%) and 13 (18%) patients, respectively. No simultaneous aberrations were found. Compared with patients with RAS mutation or without any aberrations, patients with PTPN11 mutation were significantly older at diagnosis and had higher fetal Hb levels, both of which have been recognized as poor prognostic factors. As was expected, overall survival was lower for patients with the PTPN11 mutation than for those without (25 versus 64%; p = 0.0029). In an analysis of 48 patients who received hematopoietic stem cell transplantation, PTPN11 mutations were also associated with poor prognosis for survival. Mutation in PTPN11 was the only unfavorable factor for relapse after hematopoietic stem cell transplantation (p = 0.001). All patients who died after relapse had PTPN11 mutation. These results suggest that JMML with PTPN11 mutation might be a distinct subgroup with specific clinical characteristics and poor outcome.

Juvenile myelomonocytic leukemia: a report from the 2nd International JMML Symposium

Juvenile myelomonocytic leukemia (JMML) is an aggressive childhood myeloproliferative disorder characterized by the overproduction of myelomonocytic cells. JMML incidence approaches 1.2/million persons in the United States (Cancer Incidence and Survival Among Children and Adolescents: United States SEER Program 1975-1995). Although rare, JMML is innately informative as the molecular genetics of this disease implicates hyperactive Ras as an essential initiating event. Given that Ras is one of the most frequently mutated oncogenes in human cancer, findings from this disease are applicable to more genetically diverse and complex adult leukemias. The JMML Foundation (www.jmmlfoundation.org) was founded by parent advocates dedicated to finding a cure for this disease. They work to bring investigators together in a collaborative manner. This article summarizes key presentations from The Second International JMML Symposium, on 7-8 December 2007 in Atlanta, GA. A list of all participants is in Supplementary Table.

A conditioning regimen of busulfan, fludarabine, and melphalan for allogeneic stem cell transplantation in children with juvenile myelomonocytic leukemia

A pilot study was undertaken using a myeloablative conditioning with fludarabine, busulfan, and melphalan to improve the outcome of HSCT in 10 children, aged six months to six yr, with JMML. All patients were conditioned with oral busulfan (560 mg/m(2)), fludarabine (120 mg/m(2)), and melphalan (180-210 mg/m(2)) prior to HSCT, and received stem cells from bone marrow in seven cases, and from cord blood in three cases. Engraftment was documented in eight patients, whereas graft failure occurred in two, one of whom had received HLA-mismatched cord blood and other had received bone marrow from HLA-mismatched mother. Three patients, including two in who graft failure had occurred, relapsed. Five patients developed acute GVHD and two developed chronic GVHD. Seven patients are alive and in remission 27-69 months after transplantation. Thus, our study showed that HSCT following conditioning with fludarabine, busulfan, and melphalan was well tolerated and appeared to be effective for JMML.

Indications and donor selections for allogeneic stem cell transplantation in children with hematologic malignancies

Allogeneic stem cell transplantation (SCT) is the only curative approach for many patients with advanced or high-risk leukemia. Advances in supportive care and management of graft-versus-host disease have resulted in improvements in outcomes of related and unrelated donor SCT, creating controversies as to which strategy might be the optimal therapy for individual patients. This article discusses the indications and donor selection strategies for SCT in patients with malignant hematologic disease.