Unrelated donor bone marrow transplantation for children with juvenile myelomonocytic leukaemia

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.

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.

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.

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.

Determination of intracellular fludarabine triphosphate in human peripheral blood mononuclear cells by LC-MS/MS

Fludarabine is a nucleoside analog routinely used in conditioning regimens of pediatric allogeneic stem cell transplantation to promote stem cell engraftment. In children, it remains a challenge to accurately and precisely quantify the active intracellular triphosphate species of fludarabine in vivo, primarily due to limitations on blood volume and inadequate assay sensitivity. Here we report a liquid chromatography tandem mass spectrometry (LC-MS/MS) method for determination of fludarabine triphosphate in human peripheral blood mononuclear cells (PBMC). PBMC (∼5 million cells) were collected and lysed in 1mL 70% methanol containing 1.2mM tris buffer (pH 7.4). The lysate (80μL) was mixed with internal standard (2-chloro-adenosine triphosphate, 150ng/mL, 20μL) and injected onto an API5000 LC-MS/MS system. Separation was achieved on a hypercarb column (100mm×2.1mm, 3μm) eluted with 100mM ammonium acetate (pH 9.8) and acetonitrile in a gradient mode at a flow rate of 0.4mL/min. Multiple reactions monitoring (MRM) and electrospray ionization in negative mode (ESI(-)) were used for detection. The ion pairs 524.0/158.6 for the drug and 540.0/158.8 for the IS were selected for quantification and 524.0/425.7 used for confirmation. Retention time was 3.0 and 3.4min for fludarabine triphosphate and the IS, respectively. The concentration range for the calibration curve was 1.52-76nM. Our method is simple, fast, and has been successfully applied in a clinical dose-concentration study in children to quantify intracellular fludarabine in low volume clinical samples. The median concentration was 1.03 and 3.19pmole/million PBMC at trough and peak time points, respectively. Fludarabine triphosphate is degraded in water within hours but relatively stable in 70% methanol-tris (1.2mM, pH 7.4). One limitation is that the hypercarb column takes a longer time to equilibrate than conventional reverse phase columns, and peaks become broad and distorted if the column is not washed and stored properly.

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.

Stem cell transplant as an immunomodulatory tool for children with hematologic malignancies

Allogeneic stem cell transplantation (alloHSCT) is the most common and effective form of immunotherapy used for treatment of pediatric leukemias. A combination of graft manipulation, donor selection, fine-tuning of conditioning regimens, and use of lower and novel forms of immunosuppression following transplant has maximized the tolerability of alloHSCT in children. This outcome has facilitated new advances in disease-specific transplant regimens that seek to amplify the antitumor effects of the allograft, while reducing transplant-related mortality. However, disease relapse remains the preeminent challenge to the success of transplantation as a modality for successful treatment of high-risk disease. Separating graft versus host disease (GVHD) from graft versus leukemia (GVL) remains the most significant obstacle to enhancing disease-free survival. However, with increased clarity and discrimination in the effector mechanisms responsible for GVHD and/or GVL in patients of all ages, a new wave of clinical trials has become feasible that harnesses GVL effects to treat patients with high-risk myeloid and lymphoid malignancies. Exciting progress is being made in the use of alloHSCT with donor lymphocyte infusions (DLIs) in almost all forms of pediatric hematologic malignancies. This advance sets the stage for the use of HSCT and/or DLI in conjunction with novel disease-specific post-transplant therapies using small molecule therapeutics, tumor vaccines, and novel antibody therapies.

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.

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.

Hematopoietic stem cell transplantation for leukemia

Leukemia represents the most common pediatric malignancy, accounting for approximately 30% of all cancers in children less than 20 years of age. Most children diagnosed with leukemia are cured without hematopoietic stem cell transplantation (HSCT), but for some high-risk subgroups, allogeneic HSCT plays an important role in their therapeutic approach. The characteristics of these high-risk subgroups and the role of HSCT in childhood leukemias are discussed.

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.

Myelodysplastic and myeloproliferative disorders in children

PURPOSE OF REVIEW

Myelodysplastic and myeloproliferative disorders are clonal myeloid malignancies characterized by the triad of a growth advantage of clonal cells, disturbed differentiation and increased apoptosis. The rarity of these disorders in children and the lack of a widely accepted classification have contributed to the paucity of reports on these malignancies in the pediatric literature. A number of significant advances have been achieved in recent years. The present review will focus on diagnostics and therapy.

RECENT FINDINGS

International consensus has been achieved on classifying these disorders into three main groups; myelodysplastic syndrome (MDS), myeloid leukemia of Down syndrome (ML-DS) and juvenile myelomonocytic leukemia (JMML). In the last few years we have witnessed important advances, especially regarding the therapy of these disorders, and we have gained insights into the molecular pathogenesis of ML-DS and JMML.

SUMMARY

Classification of myelodysplastic and myeloproliferative disorders has been facilitated. Chemotherapy regimens for ML-DS have been reduced, resulting in fewer toxic deaths and improved survival. The results of stem-cell transplantation for MDS and JMML have improved. Insight into the molecular mechanisms involved may open new therapeutic avenues.

Simultaneous control of third-degree graft-versus-host disease and prevention of recurrence of juvenile myelomonocytic leukemia (JMML) with 6-mercaptopurine following fulminant JMML relapse early after KIR-mismatched bone marrow transplantation

The authors describe a young boy with juvenile myelomonocytic leukemia (JMML) who relapsed 45 days after HLA and killer immunoglobulin-like receptor (KIR) mismatched unrelated donor bone marrow transplant (MMUD-BMT) and subsequently developed life-threatening graft-versus-host disease (GvHD). Treatment with 6-mercaptopurine (6-MP) appeared to control severe GvHD and possibly prevented recurrence of leukemic relapse.

Allogeneic bone marrow transplantation for juvenile myelomonocytic leukemia: a single center experience of 23 patients

Juvenile myelomonocytic leukemia (JMML) is a childhood leukemia for which allogeneic BMT is the only curative therapy. At our pediatric stem cell transplantation unit, we performed 26 BMTs in 23 children (age 0.5–12.7 years). Conditioning was CY/TBI based (1980–1996, n=14) or BU/CY/melphalan based (1996–2001, n=9). Donors were HLA-identical siblings (n=11), unrelated volunteers (n=9) or mismatched family members (n=3). A total of 10 patients survive in CR (median follow-up 6.8 years, range 3.1–22.2 years). Relapse or persistent disease was observed in eight and two patients, respectively. Nine of these patients died, one achieved a second remission following acute nonlymphatic leukemia chemotherapy (duration to date 5.3 years). Transplant-related mortality occurred in four patients. Overall survival at 5 and 10 years was 43.5%. Using T-cell-depleted, one-antigen mismatched unrelated donors was the only significant adverse factor associated with relapse in multivariate analysis (P=0.039, hazard ratio 4.9). Together with a trend towards less relapse in patients with graft-versus-host-disease and in patients transplanted with matched unrelated donors, this suggests a graft-versus-leukemia effect of allogeneic BMT in JMML.

Donor leukocyte infusion after hematopoietic stem cell transplantation in patients with juvenile myelomonocytic leukemia

Juvenile myelomonocytic leukemia (JMML) is a clonal myeloproliferative disorder of early childhood. In all, 21 patients with JMML who received donor leukocyte infusion (DLI) after allogeneic hematopoietic stem cell transplantation (HSCT) for either mixed chimerism (MC, n=7) or relapse (n=14) were studied. Six patients had been transplanted from an HLA-matched sibling and 15 from other donors. Six of the 21 patients (MC: 3/7 patients; relapse: 3/14 patients) responded to DLI. Response rate was significantly higher in patients receiving a higher total T-cell dose (> or =1 x 10(7)/kg) and in patients with an abnormal karyotype. None of the six patients receiving DLI from a matched sibling responded. Response was observed in five of six patients who did and in one of 15 children who did not develop acute graft-versus-host disease following DLI (P=0.01). The overall outcome was poor even for the responders. Only one of the responders is alive in remission, two relapsed, and three died of complications. In conclusion, this study shows that some cases of JMML may be sensitive to DLI, this providing evidence for a graft-versus-leukemia effect in JMML. Infusion of a high number of T cells, strategies to reduce toxicity, and cytoreduction prior to DLI may improve the results.

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.

Allogeneic bone marrow transplantation in children with myelodysplastic syndrome or juvenile myelomonocytic leukemia: the Seattle experience

The purpose of this study was to evaluate the role of allogeneic bone marrow transplantation (BMT) in children with myelodysplastic syndrome (MDS). In total, 94 consecutive pediatric patients with MDS received an allogeneic BMT from 1976 to 2001 for refractory anemia (RA) (n=25), RA with ringed sideroblasts (RARS) (n=2), RA with excess blasts (RAEB) (n=20), RAEB in transformation (RAEB-T) (n=14), juvenile myelomonocytic leukemia (JMML) (n=32) or chronic myelomonocytic leukemia (CMML) (n=1). The estimated 3-year probabilities of survival, event-free survival (EFS), nonrelapse mortality and relapse were 50, 41, 28 and 29%, respectively. Patients with RA/RARS had an estimated 3-year survival of 74% compared to 68% in those with RAEB and 33% in patients with JMML/CMML. In multivariable analysis, patients with RAEB-T or JMML were 3.9 and 3.7 times more likely to die compared to those with RA/RARS and RAEB (P=0.005 and 0.004, respectively). Patients with RAEB-T were 5.5 times more likely to relapse (P=0.01). The median follow-up among the 43 surviving patients is 10 years (range 1-25). We conclude that allogeneic BMT for children with MDS is well tolerated and can be curative.

Risk factors in pediatric stem cell transplantation for leukemia

To investigate which factors impact on survival, relapse, relapse free survival, transplant-related mortality (TRM) and graft-versus-host disease (GVHD) in children who undergo allogeneic stem cell transplantation, we included all 181 children transplanted due to leukemia at our unit. At the end of follow up 54% of the patients were alive, 27% had died due to relapse while 19% had died of other causes. Survival was similar in recipients of related (55%) and unrelated grafts (48%). Risk factors identified in univariate analysis were brought into a multivariable analysis. However, an unrelated donor was not identified as a risk factor for any of the five end-points analysed. A donor positive for three to four herpes viruses increased the risk of acute GVHD, TRM and death. A female to male transplant increased the risk of TRM, particularly if combined with a mismatch. Early stage of disease as well as human leukocyte antigen (HLA)-matching independently predicted survival. The risk of relapse increased after 1992. Chronic GVHD independently decreased the risk of relapse (relative risk RR, 0.39) and death (RR 0.42). We conclude that in children with leukemia other specific donor characteristics such as HLA-matching, gender, parity, and exposure to herpes viruses were more important for outcome than relationship.

Viral Infections in Juvenile Myelomonocytic Leukemia: Prevalence and Clinical Implications

OBJECTIVES

Viral infections may complicate the diagnosis of juvenile myelomonocytic leukemia (JMML) in a substantial proportion of patients, but this possibility has not been tested in a prospective study. The authors therefore measured the cellular expression of the MxA protein, a reliable marker of viral infection, at diagnosis in children with JMML to estimate the prevalence of such infections.

METHODS

Eighteen children, aged 1 to 69 months, who met the diagnostic criteria of the International JMML Working Group were prospectively studied. MxA expression was assessed by flow cytometric analysis of peripheral blood mononuclear cells stained with an antihuman MxA antibody. All data were obtained through the MDS Committee of the Japanese Society of Pediatric Hematology.

RESULTS

Twelve patients (67%) had elevated levels of the MxA protein, with rotavirus, RS virus, or CMV infection documented in three of these patients. Although none of the patients had primary Epstein-Barr virus (EBV) infection, reactivation of the virus was strongly suspected in four children, including two with monosomy 7, each having increased levels of MxA. Southern blot analysis revealed monoclonal integration of the EBV genome into bone marrow mononuclear cells from one of these patients. There was no discernible correlation between increases in the marker protein and the presenting features or course of the disease.

CONCLUSIONS

Viral infection may be present in two thirds of children with newly diagnosed JMML, but it does not constitute a basis for revising clinical management. The possibility that EBV or other viruses contribute to JMML pathogenesis by stimulating pre-exiting malignant clones warrants further investigation.

Juvenile myelomonocytic leukemia

Juvenile myelomonocytic leukemia is an aggressive neoplasia of early childhood. Only allogeneic stem cell transplantation (SCT) offers long-term cure. In the absence of an HLA-matched family donor, early SCT from an unrelated donor is the treatment of choice for most children. With clear evidence of a graft-versus-leukemia effect and a high post-transplant relapse rate, the outcome of SCT depends, in part, on the management of immunosuppression during the procedure. The impact of pretransplant cytoreductive treatment, such as intensive chemotherapy, splenectomy, or 13-cis retinoic acid, is unclear. Hypersensitivity for granulocyte-macrophage colony-stimulating factor and pathologic activation of the Ras/MAPK pathway play an important role in the pathophysiology of juvenile myelomonocytic leukemia and provide the opportunity for several novel therapeutic approaches.

Differentiating juvenile myelomonocytic leukemia from chronic myeloid leukemia in childhood

Juvenile myelomonocytic leukemia (JMML) is a rare clonal myeloproliferative disease of early childhood. To determine the diagnostic features, appropriate treatment, and overall patient survival pertaining to JMML for children, the authors reviewed the clinical data of 16 children with JMML admitted to the National Taiwan University Hospital between 1978 and 2001. Median age at diagnosis was 2.5 years. Fever was the most common symptom at diagnosis. At initial presentation, the mean white blood count and absolute monocyte count were 30 x 10(9)/L and 4.5 x 10(9)/L, respectively. Cytogenetic analysis was performed in 14 patients, and 2 patients (14%) had monosomy 7. Another patient, with normal karyotype at diagnosis, had deletion of 7q22 at the follow-up chromosome study. Forty-seven chronic myeloid leukemia (CML) patients were also diagnosed and followed at the same hospital during the same interval period. The age, leukocyte counts, platelet counts, basophil counts, monocyte percentages on peripheral blood smears, and median survival rate showed significant differences between JMML and CML patients (P < 0.05). The median survival was 10 months and the probability of 10-month survival was 0.38 by Kaplan-Meier analysis for 12 of the 16 JMML patients who did not receive hematopoietic stem cell transplantation (HSCT). Among three patients receiving HSCT, one patient relapsed 9 months after the first HSCT and was treated successfully by a second HSCT from the same sibling donor.

Second allogeneic hematopoietic stem cell transplantation for juvenile myelomonocytic leukemia: case report and literature review

Juvenile myelomonocytic leukemia (JMML) is a rare clonal myeloproliferative disease in young childhood. Hematopoietic stem cell transplantation (HSCT) is the only way to cure the disease, but relapse after HSCT remains a major cause of treatment failure. A 5-year-old girl with JMML, who had experienced a relapse after the first transplant, did not respond to donor lymphocyte infusion and withdrawal of immune-suppressing agents. She was successfully treated using a second transplant. Detailed reports from the English literature since 1988 relating to a total of 13 JMML patients undergoing a second transplant were reviewed. Seven of the 13 JMML patients (54%) were alive and disease-free, with a median follow-up of 53 months after the second transplant. Within the first 6 months following the initial transplant, 10 JMML patients suffered either autologous recovery (n = 6) or early relapse (n = 4). Seven of the 10 (70%) were alive, with a median survival period of 53 months after the second transplant. Six JMML patients underwent retransplantation within 6 months of the first transplant, with three of these (50%) alive at follow-ups of 24, 57, and 90 months after the second procedure. The authors conclude that a second transplant within 6 months may be worth considering for JMML patients who experience autologous recovery or earlier relapse after the first transplant.

Novel regimen for the treatment of juvenile myelomonocytic leukemia (JMML)

The effective treatment for juvenile myelomonocytic leukemia (JMML) patients lacking access to stem cell transplantation remains unavailable. Here, we describe a promising result obtained with novel regimen comprised of a combination of chemotherapy and differentiation therapy. Five patients diagnosed as JMML were treated with a standard regimen (cytosine arabinoside (Ara-C) 100mg/m(2) per day continuous infusion (days 0-6), etoposide 100mg/m(2) per day (days 0-4), vincristine 1.5mg/m(2) per d (day 9) and isotretinoin 75-100mg/m(2) per day (days 10-20)). All patients responded to the standard regimen. Three of the five were later treated with salvage a regimen (Ara-C 100mg/m(2) per day continuous infusion (days 0-4), etoposide 100mg/m(2) per day (days 0-4) and Ara-C 15mg/m(2) per day SC (days 6-15)) when immature myeloid cells reappeared in the peripheral blood, the spleen increased or blast crisis occurred. Immature myeloid cells disappeared again after one cycle of salvage regimen in all patients. All patients are alive now with a median follow up duration of 27 months (8-69 months). Although the number of patients enrolled was limited, the standard and salvage regimens were found to be safe and effective alternatives for JMML patients without a matched donor. These regimens also could be used safely before stem cell transplantation.

Successful treatment of JMML relapsed after unrelated allogeneic transplant with cytoreduction followed by DLI and interferon-alpha: evidence for a graft-versus-leukemia effect in non-monosomy-7 JMML

Relapse is the major cause of treatment failure after allogeneic transplantation of children with juvenile myelomonocytic leukemia (JMML), and the role of post-transplant immunomodulation is poorly understood. We report a 12-month-old child with JMML relapsed after unrelated marrow transplantation who received cytoreduction followed by donor lymphocyte infusion (DLI) with improvement, and after addition of interferon-alpha (IFN) achieved complete donor chimerism. He was weaned from IFN and has maintained complete remission for 19 months. This is the first published report of a patient with non-monosomy-7 JMML responding to post-transplant immunomodulation and suggests a role for DLI plus IFN in these patients.

Low incidence of severe acute graft-versus-host disease in children given haematopoietic stem cell transplantation from unrelated donors prospectively matched for HLA class I and II alleles with high-resolution molecular typing

We evaluated the outcome of 63 children given haematopoietic stem cell transplantation from unrelated donors (URD-HSCT) prospectively selected using DNA high-resolution typing of both HLA class I and class II loci. Thirty patient/donor pairs (48%) were fully matched. Among the others, HSCT was performed in the presence of one (n=22), two (n=9), or three (n=2) HLA disparities. Patients had either malignant (n=46) or non-malignant (n=17) disease. In all cases, graft-versus-host disease (GVHD) prophylaxis consisted of cyclospor-in A, short-term methotrexate and pretransplant anti-thymocyte globulin. The probability of haematopoietic recovery at day 100 was 97%. Two patients experienced primary graft failure. The cumulative probability of grades III-IV acute GVHD and of extensive chronic GVHD equalled 8 and 14%, respectively. A total of 12 patients died of transplant-related complications. The probability of transplant-related mortality (TRM) at 100 and 180 days was 10 and 15%, respectively, whereas the cumulative incidence of TRM was 22%. The probability of GVHD-related mortality equalled 6% at 2.5 years. The overall and disease-free survival rates were 67 and 65%, respectively. URD-HSCT with donor selection based on high-resolution HLA typing is associated with low incidence of both severe acute GVHD and graft failure. The observed outcome is comparable to that of children transplanted from HLA-identical siblings.

Juvenile myelomonocytic leukemia

Juvenile myelomonocytic leukemia is an aggressive neoplasia of early childhood. Only allogeneic stem cell transplantation (SCT) offers a long-term cure. In the absence of an HLA-matched family donor, early SCT from an unrelated donor will be the treatment of choice for most children. With clear evidence of a graft-versus-leukemia effect and a high post-transplant relapse rate, outcome of SCT will depend, in part, on the management of immunosuppression during the procedure. The impact of pretransplant cytoreductive treatment, such as intensive chemotherapy, splenectomy, or 13-cis retinoic acid, is unclear. Hypersensitivity for granulocyte-macrophage colony-stimulating factor and pathologic activation of the Ras/MAPK pathway play an important role in the pathophysiology of juvenile myelomonocytic leukemia and will provide the opportunity for several novel therapy approaches.

Successful treatment of juvenile myelomonocytic leukemia relapsing after stem cell transplantation using donor lymphocyte infusion

Juvenile myelomonocytic leukemia (JMML) is a rare pediatric malignancy. Hematopoietic stem cell transplantation (SCT) is the only curative approach. However, relapse after SCT remains the major cause of treatment failure. Unlike most other pediatric malignancies, JMML may be susceptible to a graft-versus-leukemia (GVL) effect, although, unlike chronic myeloid leukemia, reports of response to donor lymphocyte infusions (DLIs) remain scanty. This is the first report that describes the successful treatment of relapsed JMML with DLI in the absence of further chemotherapy and provides definite proof of a GVL effect in JMML.

New approaches to hematopoietic cell transplantation in oncology

The use of high-dose chemotherapy followed by autologous HCT and the use of allogeneic HCT in children and adolescents with high-risk ALL, AML, and NBL has successfully improved outcomes. For other diseases, however, the role of HCT in treatment remains a subject of further research. The availability of HCT was significantly expanded by developing alternative graft sources that currently include BM, peripheral blood, and UCB from autologous and allogeneic related or unrelated donors. Progress in autologous HCT has been achieved by the identification of more effective and less toxic preparative regimens and by ex vivo purging of stem cell products. In allogeneic HCT, graft-versus-leukemia or graft-versus-tumor effects are being exploited increasingly to lower relapse rates. In addition, immunomodulation to promote tolerance, as well as allogeneic antitumor reactions have been achieved by antibody therapy, cytokine therapy, or cell-based immunotherapy. Future improvements are likely, as evidenced by promising preliminary results in the development of stem cell collection techniques, in vitro stem cell expansion, and purging techniques of stem cell grafts. The development of less intensive or nonmyeloablative preparative regimens may further reduce regimen-related morbidity and mortality Specific immunotherapy may facilitate tolerance induction in mismatched allogeneic HCT and support allogeneic HCT in the setting of donor-host HLA disparity. Ultimately, advances in cytokine therapy, tumor-specific vaccines, and gene therapy may decrease or even eradicate recurrence of the malignant disease after HCT.