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The chronic myeloproliferative disorders consist of chronic myelogenous leukemia, polycythemia vera (p. vera), primary myelofibrosis, essential thrombocythemia, chronic neutrophilic leukemia, and chronic eosinophilic leukemia. All of these disorders involve dysregulation at the multipotent hematopoietic stem cell (CD34), with one or more of the following shared features:
Patients with p. vera and essential thrombocythemia have marked increases of red blood cell and platelet production, respectively. Treatment is directed at reducing the excessive numbers of blood cells. Both p. vera and essential thrombocythemia can develop a spent phase late in their courses that resembles primary myelofibrosis with cytopenias and marrow hypoplasia and fibrosis.[1,2,3] A specific point mutation in one copy of the Janus kinase 2 gene (JAK2), a cytoplasmic tyrosine kinase, on chromosome 9, which causes increased proliferation and survival of hematopoietic precursors in vitro, has been identified in most patients with p. vera, essential thrombocythemia, and idiopathic myelofibrosis.[4,5,6,7,8,9] Researchers are pursuing specific targeting of this aberrant protein.
Refer to the PDQ summary on Chronic Myelogenous Leukemia Treatment for more information.
The proposed revised World Health Organization criteria for the diagnosis of polycythemia vera (p. vera) requires two major criteria and one minor criterion or the first major criterion together with two minor criteria.
Other confirmatory findings no longer required for diagnosis include:[2,3,4]
There is no staging system for this disease.
Patients have an increased risk of cardiovascular and thrombotic events and transformation to acute myelogenous leukemia or primary myelofibrosis.[5,6,7] Age older than 65 years and a history of vascular events are independent predictors of thrombosis.[5,8]
Therapy for p. vera includes intermittent, chronic phlebotomy to maintain the hematocrit below 45% in men. The target level for women may need to be lower (e.g., hematocrit <40%), but there are no empiric data to confirm this recommendation.
Complications of phlebotomy include:
(Refer to the PDQ summary on Oral Complications of Chemotherapy and Head/Neck Radiation for more information.)
In addition, progressive splenomegaly or pruritus not controllable by antihistamines may persist despite control of the hematocrit by phlebotomy. (Refer to the PDQ summary on Pruritus for more information.) If phlebotomy becomes impractical, hydroxyurea or interferon-alpha can be added to control the disease.
The Polycythemia Vera Study Group randomly assigned more than 400 patients to phlebotomy (target hematocrit <45), radioisotope phosphorous-32 (2.7 mg/m2 administered intravenously every 12 weeks as needed), or chlorambucil (10 mg administered by mouth daily for 6 weeks, then given daily on alternate months). The median survival for the phlebotomy group (13.9 years) and the radioisotope phosphorous-32 group (11.8 years) was significantly better than that of the chlorambucil group (8.9 years), primarily because of excessive late deaths from leukemia or other hematologic malignancies.[Level of evidence: 1iiA] Because of these concerns, many clinicians use hydroxyurea for patients who require cytoreductive therapy that is caused by massive splenomegaly, a high phlebotomy requirement, or excessive thrombocytosis.
In a pooled analysis of 16 different trials, interferon-alpha therapy resulted in avoidance of phlebotomy in 50% of patients, with 80% of patients experiencing marked reduction of splenomegaly.[Level of evidence: 3iiiDiv] Interferon posed problems of cost, side effects, and parenteral route of administration, but no cases of acute leukemia were seen in this analysis. When patients are poorly compliant with phlebotomy or issues of massive splenomegaly, leukocytosis, or thrombocytosis supervene, treatment with interferon or pegylated interferon is considered for patients younger than 50 years (who are more likely to tolerate the side effects and benefit from a lack of transformation to leukemia), while hydroxyurea is considered for patients older than 50 years.[2,13]
A phase II study (PVN1) provided evidence that V617F JAK2 mutation is a reliable molecular marker of p. vera and is potentially useful in monitoring treatment effect.
In a Cochrane review of two randomized studies of 630 patients with no clear indication or contraindication for aspirin, those receiving 100 mg of aspirin versus placebo had reduction of fatal thrombotic events, but this benefit was not statistically significant (OR = 0.20; 95% CI, .03–1.14). A retrospective review of 105 patients who underwent surgery documented 8% thromboembolism and 7% major hemorrhage with prior cytoreduction by phlebotomy and postoperative subcutaneous heparin in one half of the patients.
Guidelines based on anecdotal reports have been developed for the management of pregnant patients with p. vera.
Current Clinical Trials
Check for U.S. clinical trials from NCI's list of cancer clinical trials that are now accepting patients with polycythemia vera. The list of clinical trials can be further narrowed by location, drug, intervention, and other criteria.
General information about clinical trials is also available from the NCI Web site.
Primary myelofibrosis (also known as agnogenic myeloid metaplasia, chronic idiopathic myelofibrosis, myelosclerosis with myeloid metaplasia, and idiopathic myelofibrosis) is characterized by splenomegaly, immature peripheral blood granulocytes and erythrocytes, and teardrop-shaped red blood cells. In its early phase, the disease is characterized by elevated numbers of CD34-positive cells in the marrow, while the later phases involve marrow fibrosis with decreasing CD34 cells in the marrow and a corresponding increase in splenic and liver engorgement with CD34 cells.
As distinguished from chronic myelogenous leukemia (CML), primary myelofibrosis usually presents as follows:
In addition to the clonal proliferation of a multipotent hematopoietic progenitor cell, an event common to all chronic myeloproliferative disorders, myeloid metaplasia is characterized by colonization of extramedullary sites such as the spleen or liver.[3,4]
Most patients are older than 60 years at diagnosis, and 33% of patients are asymptomatic at presentation. Splenomegaly, sometimes massive, is a characteristic finding.
(Refer to the PDQ summaries on Pain; Fatigue; Fever, Sweats, and Hot Flashes; and Nutrition for information on many of the symptoms listed above.)
The proposed World Health Organization criteria for the diagnosis of primary myelofibrosis requires all three major criteria and two minor criteria.
Distinguishing prefibrotic myelofibrosis from essential thrombocythemia can be difficult because of substantial interobserver variability and because of no difference in clinical outcome.
The median survival is 3.5 years to 5.5 years, but patients younger than 55 years have a median survival of 11 years.[3,4] The major causes of death include:
Fatal and nonfatal thrombosis was associated with age more than 60 years and JAK2 positivity in a multivariable analysis of 707 patients followed from 1973 to 2008. Bone marrow examination including cytogenetic testing may exclude other causes of myelophthisis, such as CML, myelodysplastic syndrome, metastatic cancer, lymphomas, and plasma cell disorders. In acute myelofibrosis, patients present with pancytopenia but no splenomegaly or peripheral blood myelophthisis. Peripheral blood or marrow monocytosis is suggestive for myelodysplasia in this setting.
Prognostic factors include:[9,10,11,12,13]
Patients without any of these adverse features, excluding age, have a median survival of more than 10 years, while the presence of any two of these adverse features lowers the median survival to less than 3 years. An international prognostic scoring system has been proposed by the Working Group for Myelofibrosis Research and Treatment.
Karyotype abnormalities can also affect prognosis. In a retrospective series of 200 patients, 13q and 20q deletions and trisomy 9 correlated with improved survival and no leukemia transformation in comparison to the trisomy 8 or a complex karyotype.
The profound anemia that develops in this disease usually requires red blood cell transfusion. Red blood cell survival is markedly decreased in some patients; this can sometimes be treated with glucocorticoids. Disease-associated anemia may occasionally respond to the following:[4,15,16,17]
JAK2 inhibitors are being evaluated in randomized trials, and patients may be eligible even in the absence of a JAK2 mutation.(COMFORT-I trial [NCT00952289])
Painful splenomegaly can be treated temporarily with chemotherapy (hydroxyurea), interferon, thalidomide, lenalidomide, or radiation therapy, but often requires splenectomy.[17,18] The decision to perform splenectomy represents a weighing of the benefits (i.e., reduction of symptoms, decreased portal hypertension, and less need for red blood cell transfusions) versus the debits (i.e., postoperative mortality of 10% and morbidity of 30% caused by infection, bleeding, or thrombosis; no benefit for thrombocytopenia; and accelerated progression to blast crisis that was seen by some investigators but not others).[4,18]
Hydroxyurea is useful in patients with this disease but may have a potential leukemogenic effect. In patients with thrombocytosis and hepatomegaly after splenectomy, cladribine has shown responses as an alternative to hydroxyurea. The use of interferon-alpha can result in hematologic responses, including reduction in spleen size in 30% to 50% of patients, though many patients do not tolerate this medication.[20,21] Favorable responses to thalidomide and lenalidomide have been reported in about 20% to 60% of patients.[15,16,17,22,23][Level of evidence: 3iiiDiv]
A response defined as 50% reduction of splenomegaly or development of transfusion independence was attained by one-third of 34 symptomatic patients using tipifarnib.[Level of evidence: 3iiiDiv] A more aggressive approach involves allogeneic peripheral stem cell or bone marrow transplantation when a suitable sibling donor is available.[25,26,27] Detection of the JAK2 mutation after transplantation is feasible, but there are no data to confirm that a change in therapy based on persistence of this marker would have an effect on outcome. A retrospective review of 150 patients who underwent surgery documented 8% thromboembolism and 7% major hemorrhage with prior cytoreduction and postoperative subcutaneous heparin in one-half of the patients.
Check for U.S. clinical trials from NCI's list of cancer clinical trials that are now accepting patients with primary myelofibrosis. The list of clinical trials can be further narrowed by location, drug, intervention, and other criteria.
The proposed revised World Health Organization criteria for the diagnosis of essential thrombocythemia requires all four criteria.
Patients older than 60 years or those with a prior thrombotic episode have as much as a 25% chance of developing cerebral, cardiac, or peripheral arterial thromboses and, less often, a chance of developing a pulmonary embolism or deep venous thrombosis. Similar to the other myeloproliferative syndromes, conversion to acute leukemia is found in a small percentage of patients (<10%) with long-term follow-up.
Untreated essential thrombocythemia means that a patient is newly diagnosed and has had no prior treatment except supportive care.
Controversy is considerable regarding whether asymptomatic patients with essential thrombocythemia require treatment. A randomized trial of patients with essential thrombocythemia and a high risk of thrombosis compared treatment with hydroxyurea titrated to attain a platelet count below 600,000/mm3 with a control group that received no therapy. Hydroxyurea was found to be effective in preventing thrombotic episodes (4% vs. 24%).[Level of evidence: 1iiDiv] A retrospective analysis of this trial found that antiplatelet drugs had no significant influence on the outcome. Resistance to hydroxyurea is defined as a platelet count of greater than 600,000/mcL after 3 months of at least 2 g per day of hydroxyurea or a platelet count greater than 400,000/µL and a white blood count of less than 2,500/µL or a hemoglobin less than 10 g/dL at any dose of hydroxyurea.
In a case-controlled observational study of 65 low-risk patients (<60 years of age, platelet count <1,500 × 109 /L, and no history of thrombosis or hemorrhage) with a median follow-up of 4.1 years, the thrombotic risk of 1.91 cases per 100 patient years and hemorrhagic risk of 1.12 cases per 100 patient years was not increased over the normal controls. A prospective randomized trial of 809 patients compared hydroxyurea plus aspirin versus anagrelide plus aspirin. Although the platelet-lowering effect was equivalent, the anagrelide group had significantly more thrombotic and hemorrhagic events (hazard ratio [HR] = 1.57; P = .03) and more myelofibrosis (HR = 2.92; P = .01). No differences were seen for myelodysplasia or acute leukemia.[Level of evidence: 1iiA] Many clinicians use hydroxyurea or platelet apheresis prior to elective surgery to reduce the platelet count and to prevent postoperative thromboembolism. No prospective or randomized trials document the value of this approach.
Among low-risk patients (defined as age 60 years or younger with no prior thrombotic episodes), a retrospective review of 300 patients showed benefit for antiplatelet agents in reducing venous thrombosis in JAK2-positive cases and in reducing arterial thrombosis in patients with cardiovascular risk factors.
Check for U.S. clinical trials from NCI's list of cancer clinical trials that are now accepting patients with essential thrombocythemia. The list of clinical trials can be further narrowed by location, drug, intervention, and other criteria.
Chronic neutrophilic leukemia (CNL) is a rare chronic myeloproliferative disorder of unknown etiology, characterized by sustained peripheral blood neutrophilia (>25 × 109 /L) and hepatosplenomegaly.[1,2] The bone marrow is hypercellular. No significant dysplasia is in any of the cell lineages, and bone marrow fibrosis is uncommon.[1,2] Cytogenetic studies are normal in nearly 90% of the patients. In the remaining patients, clonal karyotypic abnormalities may include +8, +9, del (20q) and del (11q).[1,3,4,5] There is no Philadelphia chromosome or BCR/ABL fusion gene. CNL is a slowly progressive disorder, and the survival of patients is variable, ranging from 6 months to more than 20 years.
Until the last few years, the treatment of CNL focused on disease control rather than cure. Once the disease progressed to a more aggressive leukemia, there was typically little chance of obtaining a long-lasting remission because of the older age of most patients as well as the acquisition of multiple poor prognostic cytogenetic abnormalities. Allogeneic bone marrow transplantation represents a potentially curative treatment modality in the management of this disorder.[6,7,8] Varying success has been reported with the use of traditional chemotherapies including hydroxyurea and interferon.
Check for U.S. clinical trials from NCI's list of cancer clinical trials that are now accepting patients with chronic neutrophilic leukemia. The list of clinical trials can be further narrowed by location, drug, intervention, and other criteria.
Chronic eosinophilic leukemia (CEL) is a chronic myeloproliferative disorder of unknown etiology in which a clonal proliferation of eosinophilic precursors results in persistently increased numbers of eosinophils in the blood, bone marrow, and peripheral tissues. In CEL, the eosinophil count is greater than or equal to 1.5 × 109 /L in the blood. To make a diagnosis of CEL, there should be evidence for clonality of the eosinophils or an increase in blasts in the blood or bone marrow. In many cases, however, it is impossible to prove clonality of the eosinophils, in which case, if there is no increase in blast cells, the diagnosis of idiopathic hypereosinophilic syndrome (HES) is preferred. Because of the difficulty in distinguishing CEL from HES, the true incidence of these diseases is unknown, though they are rare. In about 10% of patients, eosinophilia is detected incidentally. In others, the constitutional symptoms found include:[1,2]
No single or specific cytogenetic or molecular genetic abnormality has been identified in CEL.
(Refer to the PDQ summaries on Fever, Sweats, and Hot Flashes; Fatigue; Cardiopulmonary Syndromes; Pain; Pruritus; and Gastrointestinal Complications for information on many of the symptoms listed above.)
The optimal treatment of CEL remains uncertain, partially on account of the rare incidence of this chronic myeloproliferative disorder and the variable clinical course, which can range from cases with decades of stable disease to cases with rapid progression to acute leukemia. Case reports suggest that treatment options include bone marrow transplantation and interferon-alpha.[3,4]
Treatment of HES has included the following:[5,6]
Case reports suggest symptomatic responses to imatinib mesylate for patients with HES who have not responded to conventional options.[6,7,8][Level of evidence: 3iiiDiv] Imatinib mesylate acts as an inhibitor of a novel fusion tyrosine kinase, FIP1L1-PDGFR alpha fusion tyrosine kinase, which results as a consequence of interstitial chromosomal deletion.[6,9][Level of evidence: 3iiiDiv] HES with the FIP1L1-PDGFR alpha fusion tyrosine kinase translocation has been shown to respond to low-dose imatinib mesylate.
Check for U.S. clinical trials from NCI's list of cancer clinical trials that are now accepting patients with chronic eosinophilic leukemia. The list of clinical trials can be further narrowed by location, drug, intervention, and other criteria.
The PDQ cancer information summaries are reviewed regularly and updated as new information becomes available. This section describes the latest changes made to this summary as of the date above.
Editorial changes were made to this summary.
Purpose of This Summary
This PDQ cancer information summary for health professionals provides comprehensive, peer-reviewed, evidence-based information about the treatment of chronic myeloproliferative disorders. It is intended as a resource to inform and assist clinicians who care for cancer patients. It does not provide formal guidelines or recommendations for making health care decisions.
Reviewers and Updates
This summary is reviewed regularly and updated as necessary by the PDQ Adult Treatment Editorial Board, which is editorially independent of the National Cancer Institute (NCI). The summary reflects an independent review of the literature and does not represent a policy statement of NCI or the National Institutes of Health (NIH).
Board members review recently published articles each month to determine whether an article should:
Changes to the summaries are made through a consensus process in which Board members evaluate the strength of the evidence in the published articles and determine how the article should be included in the summary.
The lead reviewers for Chronic Myeloproliferative Disorders Treatment are:
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Levels of Evidence
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National Cancer Institute: PDQ® Chronic Myeloproliferative Disorders Treatment. Bethesda, MD: National Cancer Institute. Date last modified <MM/DD/YYYY>. Available at: http://cancer.gov/cancertopics/pdq/treatment/myeloproliferative/HealthProfessional. Accessed <MM/DD/YYYY>.
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Last Revised: 2012-07-13
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