Risk-adapted therapy in essential thrombocythemia and polycythemia vera

Overview of dyslipidemia and metabolic syndrome in myeloproliferative neoplasms

Myeloproliferative neoplasms (MPNs) occur due to the abnormal proliferation of one or more terminal myeloid cell lines in peripheral blood. Subjects suffering from MPNs display a high burden of cardiovascular risk factors, and thrombotic events are often the cause of death in this population of patients. Herein, we provide a brief overview of dyslipidemia and metabolic syndrome and their epidemiology in MPNs and examine the common molecular mechanisms between dyslipidemia, metabolic syndrome, and MPNs, with a special focus on cardiovascular risk, atherosclerosis, and thrombotic events. Furthermore, we investigate the impact of dyslipidemia and metabolic syndrome on the occurrence and survival of thrombosis in MPN patients, as well as the management of dyslipidemia in MPNs, and the impact of MPN treatment on serum lipid concentrations, particularly as side/adverse effects reported in the context of clinical trials.

Thrombosis in Pregnant Women with Hematological Malignancies: A Case-Based Review

Cancer and pregnancy induce a procoagulant environment which may lead to maternal and fetal complications, such as venous thromboembolism, fetal growth restriction, and fetal loss. The incidence of hematological malignancies diagnosed during pregnancy is rising, and thrombotic events in such malignancies are not rare. Management of thrombosis during pregnancy poses a therapeutic challenge, that is further exacerbated by the impact of cancer. The available data on managing pregnant women with hematological malignancies are limited to those with myeloproliferative neoplasms, mainly essential thrombocythemia, and, to a lesser extent, polycythemia vera. Low-dose aspirin is recommended throughout pregnancy, and considering treatment with low-molecular-weight heparin and interferon formulations is advised for high-risk patients. Currently, guidelines for handling thrombotic events in pregnant women with lymphoma or leukemia are lacking, and their management is based on data extrapolated from retrospective studies, and guidelines for prevention and treatment of cancer-associated thrombosis. The present case-based review will focus on the complex issue of thrombotic risk in pregnant women with hematological malignancies, specifically myeloproliferative neoplasms, lymphomas, and leukemias.

Determination of cerebral blood flow velocity and microembolic signals in essential thrombocytosis by transcranial doppler ultrasonography

OBJECTIVES

The goal of treatment in essential thrombocytosis (ET) is to prevent vascular complications such as thrombosis and hemorrhage. This study aimed to evaluate the risk of cerebrovascular microembolism in ET patients due to detection of microembolic signals (MES) and measure cerebral blood flow velocity (CBFV) by Transcranial Doppler (TCD) ultrasonography.

MATERIAL AND METHODS

In this prospective case-control study, forty patients with diagnosed ET and age and sex-matched forty healthy controls were examined by the TCD sonography.

RESULTS

The ET group had a higher rate of MES (8/40) in the right MCA than that in the control group (none), as measured by TCD. Five patients had MES at the left MCA compared to that in no subjects in the control group. The comparison of the ET and control groups in terms of CBFV parameters showed significantly lower end-diastolic FV at the right MCA in the ET group compared to that in the control group (p < 0.05). On the other hand; both pulsatility and resistance indices in the right and left MCA and the ratios of systolic to diastolic blood flow rates in the right and left MCA were significantly higher in the ET group than that in the control group.

DISCUSSION

This study revealed that MES seems to be more common in patients with ET despite treatment. We could suggest that ET patients should be monitored more closely to address the potential risk of developing a cerebrovascular disease, which can be estimated by detection MES and raised CBFV, combine antiplatelet therapies to standard treatments.

Cardiovascular Risk in Polycythemia Vera: Thrombotic Risk and Survival: Can Cytoreductive Therapy Be Useful in Patients with Low-Risk Polycythemia Vera with Cardiovascular Risk Factors?

BACKGROUND/AIMS

Cardiovascular risk factors are not considered in the current scores for evaluation of the thrombotic risk in myeloproliferative neoplasms, and in polycythemia vera (PV) in particular. Cytoreduction is currently not indicated in low-risk patients with PV, despite the absence or presence of cardiovascular risk factors. Our purpose is to highlight how cardiovascular risk factors in patients with PV increase the thrombotic risk both in low- and high-risk patients.

METHODS

We collected and analyzed data from 165 consecutive patients with a diagnosis of PV followed at our institution and compared the frequency of thrombosis in subgroups of patients distinguished by the presence or absence of cardiovascular risk factors. The statistic tools used to obtain the results were the χ2 and the Kruskal-Wallis test for frequencies, and the Kaplan-Meyer method as well as the log-rank test for analysis of survival data.

RESULTS

The major result obtained is that the frequency of thrombotic events in our population is strictly linked with the cardiovascular risk, and it increases with the number of risk factors. Moreover, survival significantly worsens with the number of cardiovascular risk factors, despite the classical PV risk stratification.

CONCLUSION

It should be useful to design perspective studies to determine the real influence of cardiovascular risk factors on the thrombotic risk for patients with PV and on survival in order to evaluate the opportunity to develop new specific therapeutic recommendations.

The Essential Thrombocythemia, Thrombotic Risk Stratification, and Cardiovascular Risk Factors

Essential thrombocythemia is a rare hematological malignancy with good overall survival, but moderate to high risk of developing arterial or venous thrombosis lifelong. Different thrombotic risk scores for patients with essential thrombocythemia have been proposed, but only one of them (the IPSET-t scoring system) takes into account the classical cardiovascular risk factors as one of the scoring items. Currently, in clinical practice, the presence of cardiovascular risk factors in patients with diagnosis of ET rarely determines the decision to initiate cytoreductive therapies. In our study, we compared different risk models to estimate the thrombotic risk of 233 ET patients and the role of specific driver mutations and evaluated the impact that conventional cardiovascular risk factors (hypertension, cigarette smoking, diabetes, obesity, and dyslipidaemia) have on thrombotic risk in patients with ET. Perspective studies conducted on a polycentric large cohort of patients should be conducted to estimate the impact of cardiovascular risk factors in determining thrombosis in ET patients, evaluating the opportunity of initiating a cytoreductive therapy in patients with cardiovascular risk factors, even if classified into low to moderate risk groups according to other scoring systems.

Cardiovascular Risk in Essential Thrombocythemia and Polycythemia Vera: Thrombotic Risk and Survival

Thromboembolic and bleeding events pose a severe risk for patients with Polycythemia Vera (PV) and Essential Thrombocythemia (ET). Many factors can contribute to promoting the thrombotic event due to the interaction between platelets, leukocytes, and endothelium alterations. Moreover, a significant role can be played by cardiovascular risk factors (CV.R) such as cigarette smoking habits, hypertension, diabetes, obesity and dyslipidemia. In this study, we evaluated the impact that CV.R plays on thrombotic risk and survival in patients with PV and ET.

Myocardial infarction as a thrombotic complication of essential thrombocythemia and polycythemia vera

OBJECTIVE

Detailed analyses of clinical characteristics of myocardial infarction (MI) as an essential thrombocythemia (ET)- and polycythemia vera (PV)-related complication have been so far presented mostly as case reports. Therefore, the aim of this retrospective analysis was to evaluate the main cardiological and hematological characteristics for better understanding myocardial complications in ET/PV.

METHODS

A retrospective analysis was carried out involving 263 patients diagnosed with ET or PV (155/108) between 1998 and 2014. Fourteen patients suffered MI during the hematological follow-up. Their clinical characteristics were compared to 162 patients (97 ET and 65 PV patients) who did not exhibit any major thrombotic complications (MI, stroke/transient ischemic attack, and venous events) before or after hematological diagnosis of ET/PV.

RESULTS

Fourteen MI events occurred among the 263 patients (5.3%). Vascular risk factors were found in 92.9% (13/14) of analyzed cases. In all, 71.4% of the MI complications developed within 12 months after the diagnosis of ET/PV. The coronary angiography findings revealed ST-elevation MI in four cases and non-ST-elevation MI in 10. Significant stenosis of coronary arteries requiring percutaneous coronary intervention with a stent implantation was present in seven cases, while three had complex stenoses or previous grafts/stents. All of them had undergone coronary artery bypass graft operations.

CONCLUSION

The results of the present study suggest that early detection and consideration of individual management of vascular risk factors in ET/PV patients are also important. Furthermore, a better theoretic understanding of platelet activation and role of leukocytes in myeloproliferative neoplasm-related thrombosis could open new perspectives in thrombosis prediction and prevention.

Cardiac hypertrophy associated with myeloproliferative neoplasms in JAK2V617F transgenic mice

BACKGROUND

Myeloproliferative neoplasms (MPNs) are blood malignancies manifested in increased production of red blood cells, white blood cells, and/or platelets. A major molecular lesion associated with the diseases is JAK2V617F, an activation mutation form of tyrosine kinase JAK2. Cardiovascular events represent the leading cause of morbidity and mortality associated MPNs, but the underlying mechanism is not well understood.

METHODS

Previously, we generated JAK2V617F transgenic mice which displayed MPN-like phenotypes. In the present study, we further characterized these mice by analyzing the time course of MPN phenotype development and associated cardiac abnormalities. We performed detailed histochemical staining of cardiac sections.

RESULTS

JAK2V617F transgenic mice developed cardiomegaly as a subsequent event of increased blood cell production during the course of MPN phenotype development. The cardiomegaly is manifested in increased ventricular wall thickness and enlarged cardiomyocytes. Trichrome and reticulin staining revealed extensive collagen fibrosis in the heart of JAK2V617F transgenic mice. Thrombosis in the coronary artery and inflammatory cell infiltration into cardiac muscle were also observed in JAK2V617F transgenic mice, and the latter event was accompanied by fibrosis.

CONCLUSION

JAK2V617F-induced blood disorders have a major impact on heart function and lead to cardiac hypertrophy. JAK2V617F transgenic mice represent an excellent model system to study both hematological malignancies and cardiovascular diseases.

Treatment options for myelofibrosis and myeloproliferative neoplasia

SUMMARY Essential thrombocythemia, polycythemia vera and primary myelofibrosis belong to the Philadelphia chromosome negative (Ph-) myeloproliferative neoplasia (MPN) group of diseases. MPNs are clonal bone marrow stem cell disorders characterized by a proliferation of one or more of the myeloid, erythroid or megakaryocytic cell lines. The treatment of MPN patients should be carried out according to their risk stratification. In 2005 a mutation in the JAK2 gene was discovered that generated more insight into the pathogenetic working mechanism of MPNs. However, the treatment of MPN patients is still mainly only palliative, although progress is being made in reducing the symptoms for MPN patients. This review will give a general overview of the treatment of MPN patients.

Splanchnic vein thrombosis in myeloproliferative neoplasms

Splanchnic vein thrombosis (SVT) is one of the most important complications of myeloproliferative neoplasms (MPN). Although MPN are common causes of SVT, the pathophysiological mechanisms underlying this predisposition, their epidemiology and natural history are not fully understood. Studies have concentrated on the generalized prothrombotic environment generated by MPN and their relationship with abnormal blood counts, thereby furthering our knowledge of arterial and venous thrombosis in this population. In contrast, there are few studies that have specifically addressed SVT in the context of MPN. Recent research has demonstrated in patients with MPN the existence of factors increasing the risk of SVT such as the presence of the JAK2 V617F mutation and its 46/1 haplotype. Features unique to the circulating blood cells, splanchnic vasculature and surrounding micro-environment in patients with MPN have been described. There are also abnormalities in local haemodynamics, haemostatic molecules, the spleen, and splanchnic endothelial and endothelial progenitor cells. This review considers these important advances and discusses the contribution of individual anomalies that lead to the development of SVT in both the pre-neoplastic and overt stage of MPN. Clinical issues relating to epidemiology, recurrence and survival in these patients have also been reviewed and their results discussed.

JAK2 Allele Burden in the Myeloproliferative Neoplasms: Effects on Phenotype, Prognosis and Change with Treatment

The field of Philadelphia-chromosome-negative chronic myeloproliferative neoplasms (MPNs) has recently witnessed tremendous advances in the basic knowledge of disease pathophysiology that followed the identification of mutations in JAK2 and MPL. These discoveries led to a revision of the criteria employed for diagnosis by the World Health Organization. The prognostic role of the JAK2V617F mutation and of its allelic burden has been the objective of intensive research using a variety of cellular and animal models as well as in large series of patients. While a definitive position cannot yet been taken on all of the issues, there is a consensus that the presence of higher V617F allele burden, that is on the basis of a stronger activation of intracellular signalling pathways, is associated with the clinical phenotype of polycythemia vera and with defined haematological and clinical markers indicative of a more aggressive phenotype. On the other hand, a low allele burden in myelofibrosis is associated with reduced survival. Finally, a significant reduction of JAK2 V617F allele burden has been demonstrated in patients treated with interferon, while the effects of novel JAK1 and JAK2 inhibitors have not yet been fully ascertained.

Thrombosis in myeloproliferative neoplasms with JAK2V617F mutation

Myeloproliferative neoplasms (MPNs) are clonal hematopoietic stem cell disorders and are characterized by advanced proliferation and survival advantage. These abnormalities are considered to derive from the point mutation in exon 14 of the Janus kinase 2 genes (JAK2 V617F). The thrombosis rate and the high prevalence of JAK2V617F in patients with MPN suggest that there is an association between the 2 in MPN. Apart from the mutation, other variables are documented to cause endothelial dysfunction and involve in thrombotic tendency. Endothelial progenitor cells differentiated from hematopoietic stem cell in patients with JAK2V617F MPN play an indispensable role in initiating and modulating neoangiogenesis. Although a risk-oriented therapeutic approach has been applied to MPN treatments, the further study on pathogenesis of MPN may provide more novel preventions and therapies for MPN.

The association between gene polymorphisms and leukocytosis with thrombotic complications in patients with essential thrombocythemia and polycythemia vera

Objective: Vascular events are a common complication in patients with polycythemia vera (PV) and essential thrombocythemia (ET). This study aimed to analyze the association between PAI-1 4G/5G and ACE I/D gene polymorphisms, and leukocytosis with thrombosis in patients with PV and ET.

Material and Methods: In total, 64 patients with ET and PV were evaluated. Arterial or venous thrombosis, such as cerebral transient ischemic attack, ischemic stroke, myocardial infarction, peripheral arterial thrombosis, deep venous thrombosis, and pulmonary embolism, were defined as a vascular event. DNA samples were screened for mutations via reverse hybridization strip assay.

Results: In terms of PAI-1 gene polymorphism, the frequency of the 4G and 5G allele was 48.5% and 51.5%, respectively. The ACE allele frequency was 51.2% and 48.8% for D and I, respectively. There wasn’t an association between occurrence of vascular events and the frequency of any allele. In terms of occurrence of vascular events, there weren’t any significance differences between the patients that were carrying the ACE D/D homozygous allele to ACE I/D and those that carried the I/I allele (P = 0.93). There wasn’t a significant difference in occurrence of vascular events between the PAI-1 5G/5G homozygote allele carriers, and the 4G/5G and 4G/4G allele carriers (P = 0.97). Vascular events were significantly more common in the patients with leukocytosis (leukocyte count >10 × 109 L–1) than in those without leukocytosis (leukocyte count ≤10 × 109 L–1) (P = 0.00). Age >60 years was also a significant risk factor for occurrence of vascular events(P = 0.008).

Conclusion: PAI-1 and ACE gene polymorphisms were not considered new risk factors for thrombosis in PV and ET patients. On the other hand, leukocytosis at diagnosis was associated with the occurrence of vascular events in the patients with ET and PV.

Biology and clinical management of myeloproliferative neoplasms and development of the JAK inhibitor ruxolitinib

Myeloproliferative neoplasms (MPN) are debilitating stem cell-derived clonal myeloid malignancies. Conventional treatments for the BCR-ABL1-negative MPN including polycythemia vera (PV), essential thrombocythemia (ET), and primary myelofibrosis (PMF) have, so far, been unsatisfactory. Following the discovery of dysregulated JAK-STAT signaling in patients with MPN, many efforts have been directed toward the development of molecularly targeted therapies, including inhibitors of JAK1 and JAK2. Ruxolitinib (previously known as INCB018424; Incyte Corporation, Wilmington, Delaware, USA) is a rationally designed potent oral JAK1 and JAK2 inhibitor that has undergone clinical trials in patients with PV, ET, and PMF. Ruxolitinib was approved on November 16, 2011 by the United States Food and Drug Administration for the treatment of intermediate or high-risk myelofibrosis (MF), including patients with PMF, post-PV MF, and post-ET MF. In randomized phase III studies, ruxolitinib treatment resulted in significant and durable reductions in splenomegaly and improvements in disease-related symptoms in patients with MF compared with placebo or best available therapy. The most common adverse events were anemia and thrombocytopenia, which were manageable and rarely led to discontinuation. This review addresses the cellular and molecular biology, and the clinical management of MPN.

Incidence rates and risk factors for vascular events in patients with essential thrombocythemia: a multicenter study from Korea

BACKGROUND

Essential thrombocythemia (ET) is classified as a Philadelphia chromosome-negative classic myeloproliferative neoplasm. ET is a clonal stem cell disorder that is often associated with JAK2 mutations and shares phenotypic and pathogenetic similarities with other myeloproliferative neoplasms. Hemorrhagic complications and arterial and venous thrombosis are common in patients with ET. The aim of this retrospective analysis was to assess the cumulative incidence rate and risk factors for thrombohemorrhagic events in patients with ET based on a multicenter study in Korea.

PATIENTS AND METHODS

A total of 239 patients with ET, from February 1995 to April 2011, were retrospectively analyzed from 4 Korean academic institutions. Data were collected through the review of medical records, and vascular events were confirmed by diagnostic procedures for establishing thrombosis and hemorrhagic complications.

RESULTS

Of the patients (median age, 61 years; median follow-up, 51.8 months), 32 (13.4%) experienced thrombohemorrhagic complications. The 10-year cumulative incidence rate showed a 20.6% incidence of thrombohemorrhagic events. In univariate analysis, the presence of JAK2 mutations, high-risk group, previous thrombohemorrhagic events, and >60 years old were shown to have higher incidences of vascular events than any other factors. In multivariate analysis, previous thrombotic events and JAK2 mutations were independent risk factors for vascular events (hazard ratio, 2.907 [95% CI, 1.142-7.406], P =.025; and 4.146 [95% CI 1.227-14.018], P = 0.022).

CONCLUSION

Previous thrombotic history and the JAK2 V617F mutation were associated with a higher 10-year cumulative incidence rate of thrombohemorrhagic events.

JAK2 mutation and thrombosis in the myeloproliferative neoplasms

The clinical course of the classic myeloproliferative neoplasms (MPNs) is burdened by an increased rate of cardiovascular events, which are the major cause of mortality. Age and history of thrombosis are the criteria used to stratify patients to the most appropriate therapeutic options. However, the mechanisms ultimately responsible for the increased thrombotic tendency have not yet been elucidated; abnormalities of blood cell count, neutrophil and platelet activation, and a state of hypercoagulability can all occur. Recurrent mutations in JAK2 or MPL have been described in MPNs and serve as disease markers. There is also evidence that a JAK2V617F mutant state represents an independent factor associated with thrombosis, and abnormalities of cell function attributable to JAK2V617F have been characterized. It is hoped that elucidation of the role mutant JAK2 plays in MPNs will improve our understanding of the pathophysiology of thrombosis and eventually result in improved patient treatment using molecularly targeted drugs.

Insights into the pathogenesis and management of thrombosis in polycythemia vera and essential thrombocythemia

The classic myeloproliferative neoplasms (MPNs) include polycythemia vera and essential thrombocythemia; their molecular basis has been described only recently with the demonstration of recurrent mutations in JAK2 or MPL. While life expectancy may not be significantly shortened, arterial and venous thrombosis constitute the major causes of morbidity and mortality, together with disease evolution to myelofibrosis or transformation to acute leukemia. Therapy is currently aimed at reducing the rate of thrombosis without increasing the risk of hematologic transformation by inappropriate exposure to cytotoxic drugs. Nevertheless, the mechanism(s) finally responsible for the increased thrombotic tendency have not been clearly elucidated, although risk factors for thrombosis have been identified, and are currently employed for stratifying patients to the most appropriate therapeutic options. Abnormalities of blood cells, activation of neutrophils and platelets, and a hypercoagulability state, can all act in conjunction to lead to thrombosis. Intriguing data also point to the JAK2V617F mutation as both a marker and a mechanism for thrombosis. Better knowledge in the pathophysiology of these disorders, and the introduction of molecularly targeted drugs in clinical trials, anticipate the possibility of more specific and efficacious treatment of classic MPN, particularly as concerns the reduction of risk associated with vascular events.

Epigenetic therapy in myeloproliferative neoplasms: evidence and perspectives

The classic Philadelphia chromosome-negative myeloproliferative neoplasms (MPNs), which include polycythaemia vera, essential thrombocythaemia and primary myelofibrosis, originate from a stem cell-derived clonal myeloproliferation that manifests itself with variable haematopoietic cell lineage involvement; they are characterized by a high degree of similarities and the chance to transform each to the other and to evolve into acute leukaemia. Their molecular pathogenesis has been associated with recurrent acquired mutations in janus kinase 2 (JAK2) and myeloproliferative leukemia virus oncogene (MPL). These discoveries have simplified the diagnostic approach and provided a number of clues to understanding the phenotypic expression of MPNs; furthermore, they represented a framework for developing and/or testing in clinical trials small molecules acting as tyrosine kinase inhibitors. On the other hand, evidence of abnormal epigenetic gene regulation as a mechanism potentially contributing to the pathogenesis and the phenotypic diversity of MPNs is still scanty; however, study of epigenetics in MPNs represents an active field of research. The first clinical trials with epigenetic drugs have been completed recently, whereas others are still ongoing; results have been variable and at present do not allow any firm conclusion. Novel basic and translational information concerning epigenetic gene regulation in MPNs and the perspectives for therapy will be critically addressed in this review.

Role of platelet counts in the management of essential thrombocythemia: experience with anagrelide

An elevated platelet count is the hallmark of essential thrombocythemia (ET). Therapeutic control of platelet counts in ET has proven effective for minimizing the risk of bleeding complications. By contrast, the relationship between platelet count and thrombotic complications is less well defined. The beneficial effects of lowering the platelet count are greatest when levels are reduced close to or within the normal range, thus supporting the trend within the medical community to reduce platelet treatment targets to below 400-450 × 10(9)/l. Platelet counts have further utility in ET as a marker to indicate intolerance/resistance to hydroxyurea according to recently published guidelines. In the current era, where novel risk factors for ET complications are being discussed, this article takes a back-to-basics approach, considering what platelet counts reveal in practice as a risk factor for complications and a marker of treatment efficacy, with particular focus on data for the platelet-selective agent anagrelide.

ABO-blood type incompatible living donor liver transplantation in a patient with Budd-Chiari Syndrome secondary to essential thrombocythemia

Budd-Chiari syndrome (BCS) results from diverse causative factors. Myeloproliferative disorders (MPDs) including essential thrombocythemia (ET) account for a minority of BCS cases in Japan. ABO-blood-type incompatible living donor liver transplantation (LDLT) in adults has become an acceptable procedure owing to the development of new strategies for preventing antibody-mediated rejection. This report presents a rare case of BCS secondary to ET, which was cured by an ABO-incompatible (AB to A) LDLT. In this case, prostaglandin E(1) and gabexate mesilate were administered into portal vein and rituximab prophylaxis was applied. No splenectomy was performed as it is in most ABO-incompatible cases, since a flow cytometry showed no anti-B antibodies in the splenocytes collected by a wedge biopsy during the LDLT. The postoperative course was uneventful. Anti-coagulation therapy was initiated with aspirin and warfarin instead of hydroxyurea. This report describes an ABO-incompatible LDLT without a splenectomy for BCS secondary to ET.

Influence of the JAK2 V617F mutation and inherited thrombophilia on the thrombotic risk among patients with essential thrombocythemia

It is uncertain whether the JAK2 V617F mutation increases the thrombotic risk in patients with essential thrombocythemia, and it is unknown whether inherited thrombophilia is an additive risk factor in mutated subjects. We studied 132 patients with essential thrombocythemia, 38 of them (29%) with a history of thrombosis. The JAK2 mutation was present in 83 (63%), and inherited thrombophilia in 7. The mutated patients <60 years had a relative risk (RR) for thrombosis at any time of 3.83 (95%CI 1.27-11.49) in comparison with wild-type patients; in those with both the mutation and thrombophilia the RR was 2.23 (95%CI 1.57-3.18) and 7.66 (95%CI 2.66-22.03) in comparison with mutated or wild-type patients without thrombophilia, respectively. During the follow-up, only the homozygotes for JAK2 V617F were more prone to thrombosis (RR 17.25, 95%CI 2.33-127.4). Among the patients >60 years, no increase in RR was associated with the JAK2 mutation. In conclusion, in the younger patients with ET the thrombotic risk is higher in the JAK2 V617F-mutated and is further increased by the presence of inherited thrombophilia.

Clinical correlates of JAK2V617F presence or allele burden in myeloproliferative neoplasms: a critical reappraisal

JAK2 and MPL mutations are recurrent in myeloproliferative neoplasms (MPNs). A JAK2 mutation, primarily JAK2V617F, is almost invariably associated with polycythemia vera (PV). However, JAK2V617F also occurs in the majority of patients with essential thrombocythemia (ET) or primary myelofibrosis (PMF) as well as in a much smaller percentage of those with other MPNs. The mechanism(s) behind this one allele-multiple phenotypes phenomenon has not been fully elucidated. The issue is further confounded by the presence of marked variation in JAK2V617F allele burden among mutation-positive patients. In the current communication, we discuss potential mechanisms for phenotypic diversity among JAK2V617F-positive MPNs as well as review the current literature in regard to genotype-phenotype correlations (that is clinical correlates and prognostic significance) in the context of both the presence or absence of the mutation (ET and PMF) and its allele burden (PV, ET and PMF).

Steel to heal? MPD surgical conundrums

In this issue of Blood, Ruggeri and colleagues highlight the high risk of vascular events in patients with essential thrombocythemia and polycythemia vera undergoing operative procedures even with current “optimal” surgical prophylaxis.

Anticoagulation After Coronary Artery Surgery in Patients With Polycythemia Vera: Report of Two Cases

Polycythemia vera is a myeloproliferative disorder associated with the thromboembolic events. Normalization of the hematocrit and elevated platelet counts is obligatory to reduce the thrombotic risk of patients with PV. Therapeutic strategies include phlebotomy, myelosuppressive agents, and, more recently, interferon-alpha. In addition, appropriate antiplatelet therapy should be administered to prevent life-threatening complications and reducing the viscosity of the blood. Although aspirin is widely preferred in such patients, this monodrug therapy or combined with clopidogrel as an alternative approach might not be enough, especially after coronary artery surgery. Therefore, warfarin should be added to anticoagulant therapy. This short report describes the use of warfarin, associated with aspirin and clopidogrel as an anticoagulant regimen after coronary artery bypass surgery in two cases with polycythemia vera. We believe that a combination of warfarin with other oral antiplatelet agents may be more effective in preventing the coronary artery bypass graft thrombosis.

Clinical profile of homozygous JAK2 617V>F mutation in patients with polycythemia vera or essential thrombocythemia

JAK2 617V>F mutation occurs in a homozygous state in 25% to 30% of patients with polycythemia vera (PV) and 2% to 4% with essential thrombocythemia (ET). Whether homozygosity associates with distinct clinical phenotypes is still under debate. This retrospective multicenter study considered 118 JAK2 617V>F homozygous patients (104 PV, 14 ET) whose clinical characteristics were compared with those of 587 heterozygous and 257 wild-type patients. Irrespective of their clinical diagnosis, homozygous patients were older, displayed a higher leukocyte count and hematocrit value at diagnosis, and presented larger spleen volume. Aquagenic pruritus was significantly more common among homozygous PV patients. JAK2 617V>F homozygosity associated with more frequent evolution into secondary myelofibrosis in both PV and ET. After adjustment for sex, age, leukocyte count, and previous thrombosis in a multivariate analysis, homozygous ET patients displayed a significantly higher risk of cardiovascular events (hazard ratio [HR] 3.97, 95% confidence interval [CI] 1.34-11.7; P = .013) than wild-type (HR = 1.0) or heterozygous patients (HR = 1.49). No significant association of JAK2 617V>F homozygosity with thrombosis risk was observed in PV. Finally, JAK2 617V>F homozygous patients were more likely to receive chemotherapy for control of disease. We conclude that JAK2 617V>F homozygosity identifies PV or ET patients with a more symptomatic myeloproliferative disorder and is associated with a higher risk of major cardiovascular events in patients with ET.

The treatment of polycythaemia vera: an update in the JAK2 era

The clinical course of polycythaemia vera is marked by a high incidence of thrombotic complications, which represent the main cause of morbidity and mortality. Major predictors of vascular events are increasing age and previous thrombosis. Myelosuppressive drugs can reduce the rate of thrombosis, but there is concern that their use raises the risk of transformation into acute leukaemia. To tackle this dilemma, a risk-oriented management strategy is recommended. Low-risk patients should be treated with phlebotomy and low-dose aspirin. Cytotoxic therapy is indicated in high-risk patients, with the drug of choice being hydroxyurea because its leukaemogenicity is low. The recent discovery of JAK2 V617F mutation in the vast majority of polycythaemia vera patients opens new avenues for the treatment of this disease. Novel therapeutic options theoretically devoid of leukaemic risk, such as alpha-interferon and imatinib, affect JAK2 expression in some patients. Nevertheless, these drugs require further clinical experience and, for the time being, should be reserved for selected cases.

Thrombocytosis and thrombosis

The aim of this review is to discuss current diagnostic approaches to, and classification of, patients presenting with thrombocytosis, in light of novel information derived from the discovery of specific molecular abnormalities in chronic myeloproliferative disorders (CMPD), which represent the most common cause of primary thrombocytosis. The JAK2V617F and the MPLW515L/K mutations have been found in patients with essential thrombocythemia, polycythemia vera, and primary myelofibrosis, and less frequently in other myeloproliferative disorders complicated by thrombocytosis. However, neither mutation is disease specific nor is it universally present in patients with elevated platelet counts due to a CMPD; therefore, distinguishing between reactive and primary forms of thrombocytosis, as well as among the different clinical entities that constitute the CMPD, still requires a multifaceted diagnostic approach that includes as a key step the accurate evaluation of bone marrow histology. The role of elevated platelet counts in thrombosis, which represent the predominant complication of CMPD,significantly affecting prognosis and quality of life as well as, paradoxically, in the pathogenesis of the hemorrhagic manifestations, will be discussed. Established and novel potential risk factors for thrombosis, including the clinical relevance of the JAK2V617F mutation, and current management strategies for thrombocytosis are also briefly discussed.

Navigating the Evolving Paradigms in the Diagnosis and Treatment of Myeloproliferative Disorders

The diagnosis and management of the BCR-ABL–negative myeloproliferative disorders (MPDs) of polycythemia vera (PV), essential thrombocythemia (ET), and primary myelofibrosis (PMF) are at an explosive crossroads of scientific investigation and evolving paradigms since the discovery of the tyrosine kinase–activating JAK2V617F mutation in 2005. Additional discovery of relevant molecular lesions (JAK2 exon 12 mutations and c-MplW515L/K) have only further enriched our understanding of MPD pathogenesis. The improved diagnostic certainty these molecular markers provide have resulted in the modification, and simplification, of the World Health Organization (WHO) diagnostic algorithms for MPDs. Despite these scientific advances, however, the initial management of MPDs continues to rely upon a risk-based strategy to minimize the risk of vascular events with control of erythrocytosis, targeted antiplatelet therapy, and risk-based myelosuppressive therapy. No current medical therapy has altered the natural trend of the MPDs to lead to overt severe myelofibrosis or acute leukemia. Investigations into targeted therapies for MPDs are proceeding at a brisk pace with agents aimed at immunomodulation, decreasing marrow stromal reaction to the aberrant clone, DNA hypomethylation, or the inhibition of tyrosine kinases. Specific inhibition of JAK2 itself appears promising by in vitro investigations, and clinical trials with multiple agents are planned to commence enrollment in 2007. The potential impact of JAK2 inhibitors on the manifestations of the MPDs is unclear, but is awaited with great interest.

Essential thrombocythemia: a review of diagnostic and pathologic features

CONTEXT

Essential thrombocythemia (ET) is a chronic myeloproliferative disorder (CMPD) characterized predominately by thrombocytosis and abnormal megakaryocyte proliferation. The current diagnostic criteria require a combination of clinical, histologic, and cytogenetic data. The diagnosis relies largely on exclusion of other causes of thrombocytosis.

OBJECTIVE

Describe historical, clinical, and laboratory features of ET in order to understand, clarify, and more accurately diagnose this entity.

DATA SOURCES

Review contemporary and historical literature on ET and other causes of thrombocytosis.

CONCLUSIONS

ET is a relatively indolent and often asymptomatic CMPD that is characterized primarily by a sustained elevation in platelets > or = 600 x 10(3)/microL (> or = 600 x 10(9)/L), proliferating enlarged and hyperlobated megakaryocytes, and minimal to absent bone marrow fibrosis. Significant changes and revisions to the diagnostic requirements and criteria for ET have occurred during the last 30 years. Recently, a mutation in the Janus kinase 2 (JAK2) gene has been found in a significant number of cases of ET and other CMPDs. In up to 57% of ET cases, a mutation in the JAK2 gene can be detected. In the absence of a JAK2 mutation and features of another CMPD, the diagnosis of ET remains a diagnosis of exclusion after other causes of thrombocytosis have been excluded.

Current management of the myeloproliferative disorders: a case-based review

CONTEXT

Properly managed, the myeloproliferative disorders are generally compatible with prolonged survival. Challenges to the hematologist include knowing when and how best to intervene to prevent and manage complications. The cytoreductive agent of choice for these disorders is currently hydroxyurea, emerging from randomized trials beginning with those of the Polycythemia Vera Study Group.

OBJECTIVE

To examine the roles and shortcomings of interventions (including hydroxyurea, antiplatelet agents, anagrelide, interferon, thalidomide, alkylating agents, cell cytopheresis, erythropoietins, splenectomy, bone marrow transplantation, and imatinib) for myeloproliferative disorders.

DATA SOURCES

This report uses actual case histories to illustrate the roles and shortcomings of these interventions.

CONCLUSIONS

Beyond phlebotomy for polycythemia vera, patients with polycythemia vera and essential thrombocythemia can be stratified by their risk for thrombosis, which guides the institution of cytoreductive therapies. High-risk patients generally benefit from cytoreductive therapy, and hydroxyurea has emerged as the agent of choice, because alkylating agents (and P32) have high leukemogenic potentials. Anagrelide and interferon are second-line agents. The addition of low-dose aspirin is beneficial for most, helping to prevent arterial thrombotic complications. Therapy in any of these disorders should be tailored to the unique characteristics of the individual patient. With myelofibrosis, therapeutic options run the gamut from observation, erythropoietic stimulators, cytotoxic agents, splenectomy, and bone marrow transplantation. Thalidomide and imatinib have shown some utility. Future challenges are the refinement of individualized treatment strategies and the development of targeted therapies based on rapidly expanding understanding of the molecular perturbations in these disorders.

Practical management of classical myeloproliferative disorder patients: a clinician's guide

The classical myeloproliferative disorders (MPDs) are comprised of the clonal, BCR-ABL-negative, chronic myeloid disorders of essential thrombocythemia, polycythemia vera, and myelofibrosis with myeloid metaplasia. Management of these disorders remains a significant challenge due to the varied range of prognosis and phenotypic manifestations. Curative therapy, achieved in some patients through allogeneic stem cell transplantation, is elusive or inappropriate in most. Additionally, no available medical therapy has been shown to clearly improve survival or delay disease progression. Current management involves an emphasis on prevention of thrombohemorrhagic complications (through aspirin treatment, phlebotomy and cytoreduction in high-risk patients) in early-stage patients and symptomatic care in those with advanced disease. Leukemic transformation from MPDs remains a rapidly fatal complication, unresponsive to current therapies. Recent elucidation of the role of the activating tyrosine kinase mutation JAK2 (V617F) is anticipated to usher in an era of greater understanding and targeted therapy for the MPDs.

Molecular basis of the diagnosis and treatment of polycythemia vera and essential thrombocythemia

Recent insights into the molecular mechanisms of polycythemia vera (PV) and essential thrombocythemia (ET) are challenging the traditional diagnostic classification of these myeloproliferative disorders (MPDs). Clonality analysis using X-chromosome inactivation patterns has revealed apparent heterogeneity among the MPDs. The recently discovered single somatic activating point mutation in the JAK2 gene (JAK2-V617F) is found in the great majority of patients with PV, but also in many patients with phenotypically classified ET and other MPDs. In contrast to the acquired MPDs, mutations of the erythropoietin receptor and thrombopoietin receptor have been identified in familial forms of nonclonal erythrocytosis and thrombocytosis, respectively. The mechanisms of major clinical complications of PV and ET remain poorly understood. Quantitative or qualitative abnormalities of red cells and platelets do not provide clear explanations for the thrombotic and bleeding tendency in these MPDs, suggesting the need for entirely new lines of research in this area. Recently reported randomized clinical trials have demonstrated the efficacy and safety of low-dose aspirin in PV, and an excess rate of arterial thrombosis, major bleeding, and myelofibrotic transformation, but decreased venous thrombosis, in patients with ET treated with anagrelide plus aspirin compared to hydroxyurea plus aspirin.

Nitric oxide generation from hydroxyurea: significance and implications for leukemogenesis in the management of myeloproliferative disorders

The use of myelosuppressive agents to reduce the risk of thrombosis in patients with polycythemia vera (PV) and essential thrombocythemia (ET) has been associated with an increased risk of transformation to acute myeloid leukemia (AML). Whereas chlorambucil, busulfan, and radiophosphorus (32P) have been demonstrated to increase the risk of transformation, the leukemogenic potential of hydroxyurea (HU) continues to be a matter of debate. Clinical studies have suggested that HU may cause a small increase in the risk of AML, but it has proven difficult to establish whether AML is actually caused by HU or arises during the natural progression of PV and ET. Reports that HU undergoes metabolic activation to species that induce mutation appear to support the notion that it is leukemogenic. Here, we suggest that the ability of HU to induce mutation in cell culture studies results from the generation of nitrogen dioxide via the autoxidation of nitric oxide, a product of HU metabolism. However, we argue that autoxidation would not occur in vivo, leading to the conclusion that generation of the mutagen nitrogen dioxide is peculiar to cell culture systems and has little relevance to the use of HU in the management of PV and ET.

Anagrelide: a review of its use in the management of essential thrombocythaemia

Anagrelide (Agrylin, Xagrid) is an oral imidazoquinazoline agent which is indicated in Europe for the reduction of elevated platelet counts in at-risk patients with essential thrombocythaemia who are intolerant of or refractory to their current therapy, and in the US for the reduction of elevated platelet counts and the amelioration of thrombohaemorrhagic events in patients with thrombocythaemia associated with myeloproliferative disorders. Anagrelide is well established as an effective platelet-lowering agent in most patients with essential thrombocythaemia, including both treatment-naive patients and those refractory to other cytoreductive therapy. Results of the only randomised trial to date (the Primary Thrombocythaemia 1 [PT1] study) indicated that the composite primary endpoint (arterial or venous thrombosis, serious haemorrhage or death from vascular causes) occurred more often in recipients of anagrelide plus aspirin than in those receiving hydroxycarbamide (hydroxyurea) plus aspirin. This trial also indicated that the incidence of the secondary endpoints transient ischaemic attack and gastrointestinal bleeding favoured hydroxycarbamide plus aspirin, while the incidence of venous thrombosis favoured anagrelide plus aspirin. There were no differences between the groups in the incidence of secondary endpoints myocardial infarction, stroke, unstable angina, pulmonary embolism, hepatic-vein thrombosis, other serious haemorrhage or related deaths. The design of the PT1 study has been queried with respect to the heterogeneous nature of the study population (possible inclusion of patients with early myelofibrotic disease) and the concomitant use of aspirin (interaction with anagrelide causing increased bleeding events). Further data are therefore required before the role of anagrelide in essential thrombocythaemia can be finalized. In the meantime, when considering treatment options for patients with this disorder, anagrelide's positive effects on platelet function, lack of mutagenicity and lack of association with leukaemia or angiogenesis must be balanced against its comparative expense and positive inotropic effects. Thus, the role of anagrelide in the management of high-risk patients with essential thrombocythaemia will ultimately depend on individual patient assessment and future clarification of the potential leukaemogenicity of hydroxycarbamide.

Myeloproliferative disease in pregnancy and other management issues

The goal of this review is to assess the current treatment and outcomes of special clinical situations in patients with myeloproliferative disease (MPD) such as pregnancy, major thrombotic and bleeding complications and surgical interventions. However, only a limited literature to support optimal management strategies is available. Many of the proposed strategies are the results of common sense or derive from the extrapolation of data from other studies not specifically designed to solve these problems. Therefore, practical recommendations to guide clinical decisions in these settings still remain largely empirical.