Association between elevated white blood cell counts and thrombotic events in polycythemia vera: analysis from REVEAL.

ABSTRACT: Polycythemia vera (PV) is a myeloproliferative neoplasm characterized by clonal proliferation of hematopoietic progenitor cells and is associated with an increased risk of thrombotic events (TEs). Established risk factors for TEs in patients with PV include advanced age, TE history, and elevated hematocrit. Although an association of TE with elevated white blood cell (WBC) counts has been suggested by retrospective studies, this relationship needs further validation. The prospective observational study of patients with polycythemia vera in US clinical practices (REVEAL) study collected prospective clinical data from 2510 patients with PV with a median follow-up of 44.7 months (range, 2-59 months) from enrollment. Using time-dependent covariate Cox proportional hazards models, blood counts were individually modeled with sex, age, disease duration, TE history at enrollment (baseline covariates), and treatment (time-dependent covariate). Analysis of 2271 participants identified 142 TEs in 106 patients. Significant associations with initial TE occurrence during the study period were observed for hematocrit level >45% (hazard ratio [HR], 1.84; 95% confidence interval [95% CI], 1.234-2.749; P = .0028) and WBCs >11 × 109/L (HR, 2.35; 95% CI, 1.598-3.465; P < .0001). Elevated WBC count was significantly associated with initial TE occurrence in both low-risk and high-risk PV. When hematocrit was controlled at ≤45%, WBC count >12 × 109/L was significantly associated with TE occurrence (HR, 1.95; 95% CI, 1.066-3.554; P = .0300). The results support incorporation of WBC count into PV risk stratification and studies of treatment strategies, and indicate the importance of controlling both hematocrit and WBC count in disease management. This trial was registered at www.clinicaltrials.gov as #NCT02252159.

A safe and effective use of caplacizumab in pregnancy-related acquired thrombotic thrombocytopenic purpura.

Thrombotic thrombocytopenic purpura (TTP) is not uncommonly seen in pregnancy, either with the first episode or with the exacerbation of known disease. The management of TTP in pregnancy can be challenging if there is refractoriness to the use of therapeutic plasma exchange (TPE) and high-dose corticosteroids. Caplacizumab, a vWF-directed humanized antibody fragment, is approved for the treatment of acquired TTP but there is sparse data on its use in pregnant patients. Antenatal and peripartum haemorrhage is a theoretical concern with the use of the medication in the obstetric population. However, as options for treatment of TTP in the patients who have refractory disease are significantly limited, off-label use of caplacizumab to achieve disease control and prevent maternofetal morbidity and mortality is a reasonable consideration. This article described the successful use of caplacizumab in a pregnant patient with acquired TTP and the associated favourable outcome. The patient suffered an exacerbation following initial TPE and became refractory to both plasma exchange and high-dose corticosteroids. Off-label use of caplacizumab resulted in hematologic recovery and successful delivery of a healthy neonate. This case represents a contribution to the sparse literature on the use of this effective medication in an often-challenging clinical situation.

Myeloproliferative Neoplasms, Version 3.2022, NCCN Clinical Practice Guidelines in Oncology.

The classic Philadelphia chromosome-negative myeloproliferative neoplasms (MPN) consist of myelofibrosis, polycythemia vera, and essential thrombocythemia and are a heterogeneous group of clonal blood disorders characterized by an overproduction of blood cells. The NCCN Clinical Practice Guidelines in Oncology (NCCN Guidelines) for MPN were developed as a result of meetings convened by a multidisciplinary panel with expertise in MPN, with the goal of providing recommendations for the management of MPN in adults. The Guidelines include recommendations for the diagnostic workup, risk stratification, treatment, and supportive care strategies for the management of myelofibrosis, polycythemia vera, and essential thrombocythemia. Assessment of symptoms at baseline and monitoring of symptom status during the course of treatment is recommended for all patients. This article focuses on the recommendations as outlined in the NCCN Guidelines for the diagnosis of MPN and the risk stratification, management, and supportive care relevant to MF.

From Budd-Chiari syndrome to acquired von Willebrand syndrome: thrombosis and bleeding complications in the myeloproliferative neoplasms.

Thrombotic and hemorrhagic complications are prevalent in patients with essential thrombocythemia, polycythemia vera, and myelofibrosis. Given the impact on morbidity and mortality, reducing the risk of thrombosis and/or hemorrhage is a major therapeutic goal. Historically, patients have been risk stratified on the basis of traditional factors, such as advanced age and thrombosis history. However, multiple factors contribute to the thrombotic tendency, including gender, mutational profile, inflammatory stress, and abnormal cell adhesion. Management includes cardiovascular risk reduction and use of antiplatelet therapy, depending on myeloproliferative neoplasm subtype and mutational status. Anticoagulation is a mainstay of therapy for those with venous thrombosis, but practice patterns remain heterogeneous. Cytoreduction is indicated for higher-risk patients, but efficacy may depend on the involved vascular bed. Management of special situations, such as unusual site thrombosis, bleeding, the perioperative period, and pregnancy, are especially challenging. In this article, risk factors and treatment strategies for myeloproliferative neoplasm thrombosis and bleeding, including special situations, are reviewed. Insights gained from recent studies may lead to the development of a more precise risk classification and tailored therapy.

Myeloid/Lymphoid Neoplasms with Eosinophilia and TK Fusion Genes, Version 3.2021, NCCN Clinical Practice Guidelines in Oncology.

Eosinophilic disorders and related syndromes represent a heterogeneous group of neoplastic and nonneoplastic conditions, characterized by more eosinophils in the peripheral blood, and may involve eosinophil-induced organ damage. In the WHO classification of myeloid and lymphoid neoplasms, eosinophilic disorders characterized by dysregulated tyrosine kinase (TK) fusion genes are recognized as a new category termed, myeloid/lymphoid neoplasms with eosinophilia and rearrangement of PDGFRA, PDGFRB or FGFR1 or with PCM1-JAK2. In addition to these aforementioned TK fusion genes, rearrangements involving FLT3 and ABL1 genes have also been described. These new NCCN Guidelines include recommendations for the diagnosis, staging, and treatment of any one of the myeloid/lymphoid neoplasms with eosinophilia (MLN-Eo) and a TK fusion gene included in the 2017 WHO Classification, as well as MLN-Eo and a FLT3 or ABL1 rearrangement.

Thrombosis in the Philadelphia Chromosome-Negative Myeloproliferative Neoplasms.

The myeloproliferative neoplasms (MPNs) are clonal stem cell-derived diseases. This chapter focuses on the subcategory of Philadelphia (Ph) chromosome-negative classical MPNs, polycythemia vera (PV), essential thrombocythemia (ET), primary myelofibrosis (PMF). These MPNs are associated with both microvascular and macrovascular thrombosis, which may occur in the venous and arterial circulation. Erythrocytosis, leukocytosis, and increased JAK2V617F allele burden are known to be risk factors. In this chapter, we review the thrombotic and hemostatic manifestations of the Philadelphia (Ph) chromosome-negative classical MPNs, including the clinical manifestations, the pathophysiology, as well as management.

Do All Patients With Polycythemia Vera or Essential Thrombocythemia Need Cytoreduction?

Polycythemia vera (PV) and essential thrombocythemia (ET) are Philadelphia chromosome-negative chronic myeloproliferative neoplasms (MPNs), characterized by expansion of normal blood counts, bleeding, thrombosis, and the potential for transformation to myelofibrosis (MF) or acute myeloid leukemia (AML). The primary goals of treatment for MPNs are to reduce the risk of thrombosis, alleviate systemic symptom burden (eg, fatigue, pruritus, microvascular symptoms, and symptomatic splenomegaly), and to prevent transformation to MF/AML. Preventing transformation is clearly important, but not expected with current therapies. Currently, cytoreduction is advised based on vascular risk assessments, which include age and thrombosis history, as well as molecular profile in ET. Traditionally, cytoreduction has been advised only in patients with high vascular risk. Recently, a large prospective study evaluated the safety and efficacy of cytoreduction in patients with ET with less-than-high-risk vascular profiles. A larger question in the MPN field is whether cytoreduction is advisable for all patients with ET and PV, regardless of risk. This article reviews existing data on cytoreduction, evaluating hydroxyurea, interferons, and ruxolitinib in ET and PV. This review evaluates whether evidence supports a more liberal strategy of cytoreduction for all patients with ET and PV.

Systemic Mastocytosis, Version 2.2019, NCCN Clinical Practice Guidelines in Oncology.

Mastocytosis is a group of heterogeneous disorders resulting from the clonal proliferation of abnormal mast cells and their accumulation in the skin and/or in various extracutaneous organs. Systemic mastocytosis is the most common form of mastocytosis diagnosed in adults, characterized by mast cell infiltration of one or more extracutaneous organs (with or without skin involvement). The identification of KIT D816V mutation and the emergence of novel targeted therapies have significantly improved the diagnosis and treatment of systemic mastocytosis. However, certain aspects of clinical care, particularly the diagnosis, assessment, and management of mediator-related symptoms continue to present challenges. This manuscript discusses the recommendations outlined in the NCCN Guidelines for the diagnosis and management of patients with systemic mastocytosis.

NCCN Guidelines Insights: Myeloproliferative Neoplasms, Version 2.2018.

Myeloproliferative neoplasms (MPNs) are a group of heterogeneous disorders of the hematopoietic system that include myelofibrosis (MF), polycythemia vera (PV), and essential thrombocythemia (ET). PV and ET are characterized by significant thrombohemorrhagic complications and a high risk of transformation to MF and acute myeloid leukemia. The diagnosis and management of PV and ET has evolved since the identification of mutations implicated in their pathogenesis. These NCCN Guideline Insights discuss the recommendations outlined in the NCCN Guidelines for the risk stratification, treatment, and special considerations for the management of PV and ET.

Myelodysplastic Syndromes, Version 2.2017, NCCN Clinical Practice Guidelines in Oncology.

The myelodysplastic syndromes (MDS) comprise a heterogenous group of myeloid disorders with a highly variable disease course. Diagnostic criteria to better stratify patients with MDS continue to evolve, based on morphology, cytogenetics, and the presence of cytopenias. More accurate classification of patients will allow for better treatment guidance. Treatment encompasses supportive care, treatment of anemia, low-intensity therapy, and high-intensity therapy. This portion of the guidelines focuses on diagnostic classification, molecular abnormalities, therapeutic options, and recommended treatment approaches.

Regulatory effects of SKAR in interferon α signaling and its role in the generation of type I IFN responses.

We provide evidence that S6 kinase 1 (S6K1) Aly/REF-like target (SKAR) is engaged in IFN-α signaling and plays a key role in the generation of IFN responses. Our data demonstrate that IFN-α induces phosphorylation of SKAR, which is mediated by either the p90 ribosomal protein S6 kinase (RSK) or p70 S6 kinase (S6K1), in a cell type-specific manner. This type I IFN-inducible phosphorylation of SKAR results in enhanced interaction with the eukaryotic initiation factor (eIF)4G and recruitment of activated RSK1 to 5' cap mRNA. Our studies also establish that SKAR is present in cap-binding CBP80 immune complexes and that this interaction is mediated by eIF4G. We demonstrate that inducible protein expression of key IFN-α-regulated protein products such as ISG15 and p21(WAF1/CIP1) requires SKAR activity. Importantly, our studies define a requirement for SKAR in the generation of IFN-α-dependent inhibitory effects on malignant hematopoietic progenitors from patients with chronic myeloid leukemia or myeloproliferative neoplasms. Taken altogether, these findings establish critical and essential roles for SKAR in the regulation of mRNA translation of IFN-sensitive genes and induction of IFN-α biological responses.

Practice Patterns in the Diagnosis and Treatment of Polycythemia Vera in the Post-JAK2 V617F Discovery Era.

Polycythemia vera (PV) is an acquired clonal hematopoietic stem cell disorder characterized by an overproduction of red blood cells, white blood cells, and platelets; thrombotic and hemorrhagic complications; and an increased risk of transformation to myelofibrosis and acute leukemia. In 1967, the Polycythemia Vera Study Group proposed the optimal approach to diagnosis and treatment of PV, and in 2002, investigators from Johns Hopkins University School of Medicine surveyed the practice patterns of hematologists as they pertained to PV. Since this survey, the JAK2 V617F mutation was discovered, leading to a new era of discovery in the disease pathogenesis, diagnosis, and classification and treatment of PV. Our objective was to survey hematologists in the diagnosis and treatment of PV in the modern, post-JAK2 V617F discovery era. An anonymous 17-question survey was emailed to members of the Myeloproliferative Neoplasm (MPN) Research Foundation database and Aplastic Anemia and MDS International Foundation. A total of 71 surveys were used in the analysis. Diagnostic testing varied according to the respondent's clinical experience and practice type. In addition, there were marked differences in target hematocrit and platelet count among those surveyed. There continue to be variations in diagnosis and treatment of PV despite WHO guidelines and the JAK2 discovery. US-based guidelines for MPNs are needed to create consistency in the management of PV and other MPNs.

Myeloproliferative Neoplasms, Version 2.2017, NCCN Clinical Practice Guidelines in Oncology.

Myelofibrosis (MF), polycythemia vera (PV), and essential thrombocythemia (ET) are a group of heterogeneous disorders of the hematopoietic system collectively known as Philadelphia chromosome-negative myeloproliferative neoplasms (MPNs). The diagnosis and the management of patients with MPNs have evolved since the identification of mutations that activate the JAK pathway (JAK2, CALR, and MPL mutations) and the development of targeted therapies has resulted in significant improvements in disease-related symptoms and quality of life. This manuscript discusses the recommendations outlined in the NCCN Guidelines for the diagnostic workup of MPN (MF, PV, and ET), risk stratification, treatment, and supportive care strategies for the management of MF.

Critical roles for Rictor/Sin1 complexes in interferon-dependent gene transcription and generation of antiproliferative responses.

We provide evidence that type I IFN-induced STAT activation is diminished in cells with targeted disruption of the Rictor gene, whose protein product is a key element of mTOR complex 2. Our studies show that transient or stable knockdown of Rictor or Sin1 results in defects in activation of elements of the STAT pathway and reduced STAT-DNA binding complexes. This leads to decreased expression of several IFN-inducible genes that mediate important biological functions. Our studies also demonstrate that Rictor and Sin1 play essential roles in the generation of the suppressive effects of IFNα on malignant erythroid precursors from patients with myeloproliferative neoplasms. Altogether, these findings provide evidence for critical functions for Rictor/Sin1 complexes in type I IFN signaling and the generation of type I IFN antineoplastic responses.

Historical views, conventional approaches, and evolving management strategies for myeloproliferative neoplasms.

The classical Philadelphia chromosome-negative myeloproliferative neoplasms (MPN), which include essential thrombocythemia, polycythemia vera, and myelofibrosis (MF), are in a new era of molecular diagnosis, ushered in by the identification of the JAK2(V617F) and cMPL mutations in 2005 and 2006, respectively, and the CALR mutations in 2013. Coupled with increased knowledge of disease pathogenesis and refined diagnostic criteria and prognostic scoring systems, a more nuanced appreciation has emerged of the burden of MPN in the United States, including the prevalence, symptom burden, and impact on quality of life. Biological advances in MPN have translated into the rapid development of novel therapeutics, culminating in the approval of the first treatment for MF, the JAK1/JAK2 inhibitor ruxolitinib. However, certain practical aspects of care, such as those regarding diagnosis, prevention of vascular events, choice of cytoreductive agent, and planning for therapies, present challenges for hematologists/oncologists, and are discussed in this article.

Myelodysplastic syndromes, version 2.2015.

The NCCN Guidelines for Myelodysplastic Syndromes (MDS) comprise a heterogeneous group of myeloid disorders with a highly variable disease course that depends largely on risk factors. Risk evaluation is therefore a critical component of decision-making in the treatment of MDS. The development of newer treatments and the refinement of current treatment modalities are designed to improve patient outcomes and reduce side effects. These NCCN Guidelines Insights focus on the recent updates to the guidelines, which include the incorporation of a revised prognostic scoring system, addition of molecular abnormalities associated with MDS, and refinement of treatment options involving a discussion of cost of care.

Essential role for the Mnk pathway in the inhibitory effects of type I interferons on myeloproliferative neoplasm (MPN) precursors.

The mechanisms of generation of the antineoplastic effects of interferons (IFNs) in malignant hematopoietic cells remain to be precisely defined. We examined the activation of type I IFN-dependent signaling pathways in malignant cells transformed by Jak2V617F, a critical pathogenic mutation in myeloproliferative neoplasms (MPNs). Our studies demonstrate that during engagement of the type I IFN receptor (IFNAR), there is activation of Jak-Stat pathways and also engagement of Mnk kinases. Activation of Mnk kinases is regulated by the Mek/Erk pathway and is required for the generation of IFN-induced growth inhibitory responses, but Mnk kinase activation does not modulate IFN-regulated Jak-Stat signals. We demonstrate that for type I IFNs to exert suppressive effects in malignant hematopoietic progenitors from patients with polycythemia vera, induction of Mnk kinase activity is required, as evidenced by studies involving pharmacological inhibition of Mnk or siRNA-mediated Mnk knockdown. Altogether, these findings provide evidence for key and essential roles of the Mnk kinase pathway in the generation of the antineoplastic effects of type I IFNs in Jak2V617F-dependent MPNs.

Polycythemia vera disease burden: contributing factors, impact on quality of life, and emerging treatment options.

Polycythemia vera (PV) is a chronic myeloproliferative neoplasm characterized by clonal expansion of a hematopoietic progenitor, erythrocytosis, often leukocytosis and/or thrombocytosis, and nearly always an activating mutation in Janus kinase 2 (JAK2). The PV symptom burden can be considerable, in part driven by small or large vessel thrombotic tendency, splenomegaly, fatigue, pruritus, and a chronic risk of disease transformation to myelofibrosis or acute myeloid leukemia. In addition, patients with PV have an increased risk of mortality compared with the general population that often results from cardiovascular complications or disease transformation. Further, healthcare utilization and costs are higher in patients with PV than noncancer controls. First-line therapy options for high-risk patients may effectively manage PV in some instances; however, some patients do not receive adequate benefit from current treatment options and experience a more severe disease burden as a result. This may be especially true for those patients who are resistant to or intolerant of hydroxyurea or interferon-based therapies. New treatments currently being investigated in phase 3 clinical trials may alleviate disease burden in this patient population.

Sprouty proteins are negative regulators of interferon (IFN) signaling and IFN-inducible biological responses.

Interferons (IFNs) have important antiviral and antineoplastic properties, but the precise mechanisms required for generation of these responses remain to be defined. We provide evidence that during engagement of the Type I IFN receptor (IFNR), there is up-regulation of expression of Sprouty (Spry) proteins 1, 2, and 4. Our studies demonstrate that IFN-inducible up-regulation of Spry proteins is Mnk kinase-dependent and results in suppressive effects on the IFN-activated p38 MAP kinase (MAPK), the function of which is required for transcription of interferon-stimulated genes (ISGs). Our data establish that ISG15 mRNA expression and IFN-dependent antiviral responses are enhanced in Spry1,2,4 triple knock-out mouse embryonic fibroblasts, consistent with negative feedback regulatory roles for Spry proteins in IFN-mediated signaling. In other studies, we found that siRNA-mediated knockdown of Spry1, Spry2, or Spry4 promotes IFN-inducible antileukemic effects in vitro and results in enhanced suppressive effects on malignant hematopoietic progenitors from patients with polycythemia vera. Altogether, our findings demonstrate that Spry proteins are potent regulators of Type I IFN signaling and negatively control induction of Type I IFN-mediated biological responses.

Thrombotic and bleeding complications in classical myeloproliferative neoplasms.

The Philadelphia chromosome-negative myeloproliferative neoplasms (MPNs) share an increased risk of thrombotic and hemorrhagic complications. The thromboses are more commonly arterial than venous, but unique to the BCR-ABL-negative MPNs is the involvement of the abdominal veins. Commonly accepted thrombotic risk factors include advanced age and a prior thrombotic episode, although these risk factors are associated with thrombosis regardless of the presence of an MPN. Emerging risk factors may include leukocytosis and presence of the JAK2 V617F mutation or an increase in its allelic burden. Interventions to prevent and/or treat MPN-related thromboses include aspirin, anticoagulation, and cytoreductive therapy. Although phlebotomy is a cornerstone of management in polycythemia vera to lower the risk for thrombosis, the target hematocrit is being reevaluated. Hemorrhagic complications occur with extreme thrombocytosis and may be related to acquired platelet defects such as acquired von Willebrand syndrome. The impact of new mutations and novel therapies, including JAK-inhibitors and interferon, on the thrombotic and hemorrhagic tendency remains to be determined.