The myelodysplastic/myeloproliferative neoplasms (MDS/MPN) are clonal myeloid disorders that have both dysplastic and proliferative features but are not properly classified as either myelodysplastic syndromes (MDS) or chronic myeloproliferative disorders (CMPD).[1-3] This category includes three major myeloid disorders: chronic myelomonocytic leukemia (CMML), juvenile myelomonocytic leukemia (JMML), and atypical chronic myeloid leukemia (aCML). Myeloid disease that shows features of both MDS and CMPD but does not meet the criteria for any of the three major MDS/MPN entities is designated as myelodysplastic/myeloproliferative neoplasm, unclassifiable (MDS/MPN-UC). The World Health Organization created the MDS/MPN category to provide a less restrictive view of myeloid disorders, which in some instances clearly overlap.[1-3]
The etiology of MDS/MPN is not known. The incidence of MDS/MPN varies widely, ranging from approximately 3 per 100,000 individuals older than 60 years annually for CMML to as few as 0.13 per 100,000 children from birth to 14 years annually for JMML.[4] Reliable data concerning the incidence of aCML, a recently defined entity, are not available. The incidence of MDS/MPN-UC is unknown.
The pathophysiology of MDS/MPN involves abnormalities in the regulation of myeloid pathways for cellular proliferation, maturation, and survival. Clinical symptoms result from the following complications:[5]
Patients with MDS/MPN do not have a Philadelphia chromosome or a BCR::ABL1 gene fusion.
An international consortium has proposed uniform response criteria to be used in clinical trials because of the spectrum of presentations ranging from the myelodysplastic to the myeloproliferative.[6]
The World Health Organization (WHO) classifies chronic myelomonocytic leukemia (CMML) as a myelodysplastic/myeloproliferative neoplasm (MDS/MPN).[1] The WHO recognizes a dysplastic subtype and a proliferative subtype, with prognostic groups differentiated by the circulating white blood cell (WBC) count or the percentage of blasts in the bone marrow (higher percentage with worse prognosis).[2]
CMML is a clonal disorder of a bone marrow stem cell. Monocytosis is a major defining feature. CMML exhibits heterogenous clinical, hematological, and morphological features, varying from predominantly myelodysplastic to predominantly myeloproliferative. Evolution to acute myeloid leukemia (AML) portends a particularly poor prognosis.[3]
CMML is characterized pathologically by:[4,5]
Clinical features of CMML include:[4,5]
The median age at diagnosis of CMML is 65 to 75 years with a male predominance of 1.5 to 3.1.[4,5] Because CMML is grouped with chronic myeloid leukemia in some epidemiologic surveys and with MDS in others, no reliable incidence data are available for CMML.[6] Although the specific etiology of CMML is unknown, exposure to occupational and environmental carcinogens, ionizing radiation, and cytotoxic agents has been associated in some cases.[6]
Morphologically, the disease is characterized by a persistent peripheral blood monocytosis (always >1 × 109/L) that may exceed 80 × 109/L with monocytes typically accounting for more than 10% of the WBCs.[4,5] Monocytes, though typically mature with an unremarkable morphology, can exhibit abnormal granulation, unusual nuclear lobation, or finely dispersed nuclear chromatin.[7] Fewer than 20% blasts are seen in the blood or bone marrow. Neutrophilia occurs in nearly 50% of patients with neutrophil precursors (e.g., promyelocytes and myelocytes) accounting for more than 10% of the WBCs.[8] Mild normocytic anemia is common. Moderate thrombocytopenia is often present. Bone marrow findings include:[4,5,9,10]
Hepatosplenomegaly may be present.[4,5] Autoimmune phenomena, including pyoderma gangrenosum, vasculitis, and idiopathic thrombocytopenia have been observed in CMML.[11] Care should be taken to identify cases of CMML with eosinophilia, a subtype of CMML, because of its association with severe tissue damage secondary to eosinophil degranulation. In CMML with eosinophilia, all criteria for CMML are present, and the eosinophil count in the peripheral blood is more than 1.5 × 109/L.[6]
Recurrent somatic pathogenic variants have been identified in most patients with CMML, resulting in altered signaling molecules (especially NRAS, KRAS, JAK2, and SETBP1), epigenetic regulators (especially TET2 and ASXL1), splicing factors (especially SRSF2), and transcription factors (especially RUNX1).[12-15] A CMML-specific prognostic scoring system can distinguish four risk groups based on the following factors:[16]
The best prognostic group has a median survival of more than 10 years with no leukemic evolution in the first decade of follow-up. The worst prognostic group has a median survival of 20 months with a 50% evolution to AML by 2 years.[16]
Prognostic factors associated with shorter survival include:[17,18]
Progression to acute leukemia occurs in approximately 15% to 20% of cases.[17,18]
CPSS-Mol is a CMML-specific prognostic scoring system that incorporates molecular genetic data, especially pathogenic variants in RUNX1, NRAS, SETBP1, and ASXL1. This system distinguishes low-risk disease with median survivals longer than 10 years from high-risk disease with median survivals of 2 to 4 years.[16]
CMML is a diagnosis typically made after age 70 years. The clinical course of CMML ranges from indolent or smoldering disease to an aggressive disease progression culminating in severe cytopenias or evolution to acute leukemia. Assessment of the risk factors and the pace of disease over time may help to distinguish patients who require therapy from those who would be best managed with a watchful waiting approach. Asymptomatic patients at low risk of progression may be best served by forgoing therapy.[19,20]
Patients with high-risk disease who are young enough and fit enough may undergo allogeneic SCT. This represents the only potential cure for CMML. Hypomethylating agents like azacitidine and decitabine are usually given prior to allogeneic SCT for cytoreduction or to ameliorate cytopenias.[21,22] Retrospective reports that included small numbers of patients with CMML (range, 12–80) who underwent allogeneic SCT reported recurrence rates of 20% to 40% and 5-year overall survival (OS) rates of approximately 20% to 30%.[23-28][Level of evidence C3]
A retrospective review of 1,114 patients with CMML diagnosed between 2000 and 2014 included 384 patients who underwent allogeneic SCT.[29] With a median follow-up of 51 to 78 months (in two data sets), allogeneic SCT in patients with low-risk CMML was detrimental, with a 5-year OS rates of 20% for patients who underwent allogeneic SCT and 42% for patients who did not undergo allogeneic SCT (P < .001).[29][Level of evidence C1] For patients with high-risk CMML, there was no statistically significant difference in 5-year OS rates among patients treated with or without allogeneic SCT (27% vs. 15%, respectively; P = .13).
Two randomized prospective clinical trials compared the hypomethylating agent, azacitidine, with best supportive care in patients with myelodysplastic syndromes (MDS). The trials involved large numbers of patients with MDS but also included small numbers of patients (fewer than 25) with CMML.[30,31] The overall response rates exceeded 60% for all patients who received azacitidine, but the data did not allow an assessment specifically for patients with CMML.[30,31][Level of evidence C3] Several phase II trials reported response rates of 30% to 60% for patients with CMML who received hypomethylating agents.[32-36] Azacitidine and decitabine may reverse cytopenias, cytoreduce elevated WBC counts, reduce splenic size, and improve clinical symptoms (like decreased appetite or itching).
Hydroxyurea has been given for other diseases with chronic myeloproliferation, such as thrombocythemia and myelofibrosis. These applications suggest the use of hydroxyurea for CMML with leukocytosis, thrombocytosis, or splenomegaly.[37] In a randomized prospective clinical trial of 105 patients with CMML, hydroxyurea (up to 4 g/day) was compared with etoposide.[38] With a median follow-up of 11 months, the median OS was 20 months in patients who received hydroxyurea and 9 months in patients who received etoposide (P < .0001).[38][Level of evidence A1]
In a prospective randomized trial, 170 patients with newly diagnosed advanced CMML received intravenous decitabine or hydroxyurea (1–4 g/day). With a median follow-up of 17.5 months, there was no statistically significant difference in event-free survival (12.1 months for patients who received decitabine and 10.3 months for patients who received hydroxyurea; hazard ratio, 0.83; 95% confidence interval [CI], 0.59–1.16; P = .27). There was also no statistically significant difference in median OS (16.3 months for patients who received decitabine and 21.9 months for patients who received hydroxyurea; P = .67).[39][Level of evidence A1] Although decitabine reduced CMML progression or transformation to AML by 38% compared with hydroxyurea, this was offset by a 55% increase in deaths that were not caused by progression (the deaths were usually related to infection). There are no data to suggest that systematic antibiotic prophylaxis would have helped the patients who received decitabine.
In a phase II trial, 13 hypomethylating agent–naive patients with high-risk CMML were treated with azacitidine or decitabine plus venetoclax. With a median follow-up of 14.1 months, the overall response rate was 85% (11 of 13 patients), including two with complete response and a median duration of response of 17.9 months.[40,41][Level of evidence C3] Six of these patients underwent subsequent allogeneic SCT.
A retrospective study included 21 patients with high-risk CMML who received cladribine plus low-dose cytarabine alternating with azacitidine or decitabine. The patients had an objective response rate of 33% (50% in patients with hypomethylating agent–naive CMML and 23% in patients with hypomethylating agent–failure CMML).[41][Level of evidence C3]
A phase I/II study of 23 patients with mostly high-risk MDS and greater than 5% marrow blast cells involved 10 patients with CMML. All patients received azacitidine plus venetoclax. With a median follow-up of 13.2 months, the overall response rate was 87% (95% CI, 66%–97%).[42][Level of evidence C3]
Use our advanced clinical trial search to find NCI-supported cancer clinical trials that are now enrolling patients. The search can be narrowed by location of the trial, type of treatment, name of the drug, and other criteria. General information about clinical trials is also available.
For more information, see Juvenile Myelomonocytic Leukemia Treatment.
Atypical chronic myeloid leukemia (aCML) is a leukemic disorder that exhibits both myelodysplastic and myeloproliferative features at the time of diagnosis.
Atypical CML is characterized pathologically by:[1]
Clinical features of aCML include:[1-4]
Although cytogenetic abnormalities are found in as many as 80% of the patients with aCML, none is specific.[1-3,5] No Philadelphia chromosome or BCR::ABL1 gene fusion is present.
The exact incidence of aCML is unknown. The median age at the time of diagnosis of this rare leukemic disorder is in the seventh or eighth decade of life.[1-3]
Morphologically, aCML is characterized by myelodysplasia associated with bone marrow and peripheral blood patterns similar to chronic myeloid leukemia, but cytogenetically it lacks a Philadelphia chromosome or BCR::ABL1 gene fusion.[1] The white blood cell count in the peripheral blood is variable. Median values range from 35 × 109/L to 96 × 109/L, and some patients may have white blood cell counts greater than 300 × 109/L.[1-3,5] Blasts in the peripheral blood typically account for less than 5% of the white blood cells. Immature neutrophils usually total 10% to 20% or more.[1] The percentage of monocytes is rarely more than 10%. Minimal basophilia may be present.[1-3,5] Nuclear abnormalities, such as acquired Pelger-Huët anomaly, may be seen in the neutrophils. Moderate anemia (often showing changes indicative of dyserythropoiesis) and thrombocytopenia are common.[1-4] Bone marrow findings include: [1-3,5]
The median survival times for aCML are reported to be less than 20 months, and thrombocytopenia and marked anemia are poor prognostic factors.[1,2] Atypical CML evolves to acute leukemia in approximately 25% to 40% of patients.[1,3] In the remaining patients, fatal complications include resistant leukocytosis, anemia, thrombocytopenia, hepatosplenomegaly, cerebral bleeding associated with thrombocytopenia, and infection.[3,4]
The optimal treatment of aCML is uncertain because of the rare incidence of this chronic leukemic disorder. Treatment with hydroxyurea may lead to short-lived partial remissions of 2 to 4 months in duration.[4] Atypical CML appears to respond poorly to treatment with interferon alfa.[4]
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Myelodysplastic/myeloproliferative neoplasm, unclassifiable (MDS/MPN-UC) (also known as mixed myeloproliferative/myelodysplastic syndrome, unclassifiable and overlap syndrome, unclassifiable) shows features of both myeloproliferative disease and myelodysplastic disease but does not meet the criteria for any of the other MDS/MPN entities.[1]
Diagnostic criteria for MDS/MPN-UC can be either:[1]
Clinical characteristics of MDS/MPN-UC include:
The incidence and etiology of MDS/MPN-UC are unknown.
Laboratory features typically include anemia and dimorphic erythrocytes on the peripheral blood smear.[1] Thrombocytosis (platelet count >600 × 109/L) or leukocytosis (white blood cell count >13 × 109/L) are present. Neutrophils may exhibit dysplastic features, and giant or hypogranular platelets may be present. Blasts make up less than 20% of the white blood cells and of the nucleated cells of the bone marrow. The bone marrow is hypercellular and may exhibit proliferation in any or all of the myeloid lineages. Dysplastic features are present in at least one cell line.[1]
No cytogenetic or molecular findings are available that are specific for MDS/MPN-UC. In one small series, six of nine patients (those with ringed sideroblasts associated with marked thrombocytosis [RARS-T]) had JAK2 V617F variants, which caused constitutive activation of the JAK2 tyrosine kinase. This JAK2 pathogenic variant is also commonly observed in patients with polycythemia vera, essential thrombocythemia, and idiopathic myelofibrosis.[2] Because of its rare occurrence, the prognosis and predictive factors are unknown.[1]
Adult patients with MDS/MPN associated with platelet-derived growth factor receptor gene rearrangements are candidates for imatinib mesylate at standard dosages.[3] Because of its rare occurrence, the literature only minimally addresses other treatment options for MDS/MPN-UC. Supportive care involves treating cytopenias and infection as necessary.
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This PDQ cancer information summary for health professionals provides comprehensive, peer-reviewed, evidence-based information about the treatment of myelodysplastic/myeloproliferative neoplasms. It is intended as a resource to inform and assist clinicians in the care of their patients. It does not provide formal guidelines or recommendations for making health care decisions.
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PDQ® Adult Treatment Editorial Board. PDQ Myelodysplastic/Myeloproliferative Neoplasms Treatment. Bethesda, MD: National Cancer Institute. Updated <MM/DD/YYYY>. Available at: https://www.cancer.gov/types/myeloproliferative/hp/mds-mpd-treatment-pdq. Accessed <MM/DD/YYYY>. [PMID: 26389321]
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