Leukocytosis is a risk factor for recurrent arterial thrombosis in young patients with polycythemia vera and essential thrombocythemia

There is evidence that leukocytosis is associated with an increased risk of first thrombosis in patients with polycythemia vera (PV) and essential thrombocythemia (ET). Whether it is a risk factor for recurrent thrombosis too is currently unknown. In the frame of a multicenter retrospective cohort study, we recruited 253 patients with PV (n = 133) or ET (n = 120), who were selected on the basis of a first arterial (70%) or venous major thrombosis (27.6%) or both (2.4%), and who were not receiving cytoreduction at the time of thrombosis. The probability of recurrent thrombosis associated with the leukocyte count recorded at the time of the first thrombosis was estimated by a receiver operating characteristic analysis and a multivariable Cox proportional hazards regression model. Thrombosis recurred in 78 patients (30.7%); multivariable analysis showed an independent risk of arterial recurrence (hazard ratio [HR] 2.16, 95% CI 1.12-4.18) in patients with a leukocyte count that was >12.4 x 10(9)/L at the time of the first thrombotic episode. The prognostic role for leukocytosis was age-related, as it was only significant in patients that were aged <60 years (HR for arterial recurrence 3.35, 95% CI 1.22-9.19).

Oral anticoagulant therapy in hemodialysis patients: do the benefits outweigh the risks?

Managing oral anticoagulation may be difficult in hemodialysis patients because the antithrombotic effect can be counterbalanced by an increased risk of hemorrhagic complications. There is insufficient evidence to recommend the routine use of warfarin for thrombosis prophylaxis of the vascular access in all patients. If a decision for anticoagulation is made, dosing warfarin to a "therapeutic" level is suggested, although the most appropriate target INR range remains unclear. Many hemodialysis patients with atrial fibrillation have multiple risk factors for stroke and generally benefit from warfarin, with careful and frequent laboratory monitoring. Treatment with standard dose warfarin is also recommended in patients with venous thromboembolism provided that patients do not have contraindications to anticoagulation. For those with such contraindications, placement of an inferior vena cava filter is suggested. These recommendations are limited by the almost complete lack of data in dialysis patients. Sound randomized evidence of efficacy and harm for anticoagulation in these patients will likely never be available. Knowledge of the risk of bleeding and thrombosis in anticoagulated and nonanticoagulated dialysis patients could be provided by feasible, well-designed cohort studies.

Increased risk of recurrent thrombosis in patients with essential thrombocythemia carrying the homozygous JAK2 V617F mutation

Evidence suggests that the JAK2 V617F mutation is associated with an increased risk of first thrombosis in patients with essential thrombocythemia (ET). Whether this mutation is also a risk factor for recurrent thrombosis is currently unknown. To investigate the impact of the JAK2 V617F mutation on the risk of recurrent thrombosis in patients with ET, we carried out a multicentre retrospective cohort study. We recruited 143 patients with previous arterial (64.4%) or venous major thrombosis (34.8%) or both (0.8%); 98 of them (68.5%) carried the mutation. Thrombosis recurred in 43 of the patients (30%); overall, after adjustment for sex, age, presence of vascular risk factors, and treatment after the first thrombosis, the presence of the JAK2 mutation did not predict recurrence (multivariable hazard ratio, HR, 0.88, 95% CI 0.46-1.68). Indeed, the individuals homozygous for the JAK2 V617F (allele burden >50%) mutation had an increased risk of recurrence in comparison with wild-type patients (HR 6.15, 95% CI 1.51-24.92). In conclusion, a homozygous JAK2 V617F mutation is an independent risk factor for recurrent thrombosis in patients with ET.

JAK2V617F allele burden and thrombosis: a direct comparison in essential thrombocythemia and polycythemia vera

OBJECTIVE

A direct comparison of the incidence and risk factors of major thrombosis in essential thrombocythemia (ET) and polycythemia vera (PV) according to their respective JAK2V617F allele burden is the object of this study.

MATERIALS AND METHODS

We compared the rate (%/patients/year) of major thrombosis in 867 ET patients (57% JAK2V617F) with that of 415 PV patients (all JAK2V617F) and examined risk factors.

RESULTS

Patients with ET wild-type, ET V617F, and PV showed a rate of thrombosis of 1.4%, 2.1%, and 2.7%/patients/year, respectively. The latter was found to progressively increase according to time of diagnosis. Actuarial probability of arterial and venous thrombosis in the first 5 years of diagnosis was roughly similar in the three groups. While in the subsequent periods, the curves of mutated ET patients diverged from wild-type, and after 10 to 15 years the ET-mutated arm approached PV.

CONCLUSION

These findings support the concept of a continuum between ET JAK2 mutated and PV, not only in reference to the hematological phenotype, but also in terms of vascular events.

Leukocytosis and risk stratification assessment in essential thrombocythemia

PURPOSE

Established risk factors for thrombosis in essential thrombocythemia (ET) include age and previous vascular events. We aimed to refine this risk stratification by adding baseline leukocytosis.

PATIENTS AND METHODS

We enrolled 657 patients with ET followed for a median of 4.5 years who developed 72 major thrombosis. Cox proportional hazard model was performed to analyze the thrombotic risk and to discriminate ET patients with or without thrombosis, multivariable C statistic index was used. We searched for leukocytes cutoff with the best sensitivity and specificity by a receiver operating characteristic curve.

RESULTS

Results confirmed that age and prior events are independent risk factors for thrombosis and showed a gradient between baseline leukocytosis and thrombosis. On the contrary, no significant association was found either for JAK2(V617F) allele burden and for other laboratory parameters, including platelet number. In the model with conventional risk factors alone, C statistic ratio for total thrombosis was 0.63 and when leukocytosis was added, the change was small (C = 0.67). In contrast, in younger and asymptomatic patients (low-risk category), C statistic value indicated an high risk for thrombosis in patients with leukocytosis, similar to that calculated in conventionally defined high-risk group (C = 0.65). The best leukocyte cutoff values for predicting the events was found to be 9.4 (x 10(9)/L).

CONCLUSION

We suggest to include baseline leukocytosis in the risk stratification of ET patients enrolled in clinical trials.

Recurrent thrombosis in patients with polycythemia vera and essential thrombocythemia: incidence, risk factors, and effect of treatments

BACKGROUND

Prior thrombosis is a well-established risk factor for re-thrombosis in polycythemia vera and essential thrombocythemia but scarce data are available on the rate of re-thrombosis and the optimal strategy for prevention of recurrence.

DESIGN AND METHODS

We retrospectively estimated the rate of recurrence in a multicenter cohort of 494 patients (poly-cythemia vera/essential thrombocythemia 235/259) with previous arterial (67.6%) or venous thrombosis (31%) or both (1.4%). First thrombosis was cerebrovascular disease in 191 cases, acute coronary syndrome in 106, peripheral arterial thrombosis in 44, and venous thromboembolism in 160. Microcirculatory events were not computed.

RESULTS

Thrombosis recurred in 166 patients (33.6%), with an incidence of 7.6% patient-years. Sex, diagnosis (polycythemia vera or essential thrombocythemia), and presence of vascular risk factors did not predict recurrence, whereas age >60 years did (multivariable hazard ratio [HR], 1.67; 95% confidence interval [CI] 1.19-2.32). Increased leukocyte count at the time of the first thrombosis was a risk factor for recurrence in patients <60 years old (HR 3.55; 95% CI 1.02-12.25). Cytoreduction halved the risk in the overall cohort (HR 0.53; 95% CI 0.38-0.73) and the combination with antiplatelet agents or oral anticoagulants was more effective than administration of single drugs. Significant prevention of rethrombosis was independently achieved in patients with venous thromboembolism by both oral anticoagulants (HR 0.32; 95% CI 0.15-0.64) and antiplatelet agents (HR 0.42; 95% CI 0.22-0.77), in those with acute coronary syndrome by cytoreduction (HR 0.30; 95% CI 0.13-0.68), and in those with cerebrovascular disease by antiplatelet agents (HR 0.33; 95% CI 0.16-0.66). The overall incidence of major bleeding was 0.9% patient-years and rose to 2.8% in patients receiving both antiplatelet and anti-vitamin K agents.

CONCLUSIONS

In patients with polycythemia vera and essential thrombocythemia, cytoreduction protects against recurrent thrombosis, particularly after acute coronary syndrome. The contemporary use of oral anticoagulants (after venous thromboembolism) or antiplatelet agents (after cerebrovascular disease or venous thromboembolism) further improves the protective effect. Such findings call for prospective studies aimed at investigating whether strategies tailored according to the type of first thrombosis could improve prevention of recurrences.

Postsurgery outcomes in patients with polycythemia vera and essential thrombocythemia: a retrospective survey

A multicenter retrospective analysis was performed to estimate the frequency of thrombosis and hemorrhage after surgical procedures in patients with polycythemia vera (PV) and patients with essential thrombocythemia (ET). Data from 105 patients with PV and 150 patients with ET were analyzed, for a total of 311 surgical interventions. An emergency procedure was performed in 25 (8.1%) patients; 194 surgeries were done under general anesthesia, and 21 (23%) of 91 abdominal interventions were done under laparoscopy; 155 (50.1%) were major surgeries. Subcutaneous heparin was administered in 169 (54.3%) of 311 cases and antiplatelet therapy in 48 (15.4%) of 311 case interventions. One hundred eighty-eight (74%) of 255 patients were on cytoreductive therapy before surgery. No events were observed in 259 (83.2%) of 311 procedures during 3 months of follow-up; there were 12 arterial and 12 venous thrombotic events, 23 major and 7 minor hemorrhages, and 5 deaths. Arterial thromboses were more frequent in ET (5.3% vs 1.5%; P=.08), venous events were more frequent in PV (7.7% vs 1.1%; P=.002). There was not a correlation between bleeding episodes and the type of diagnosis, use of antithrombotic prophylaxis, or type of surgery. A high proportion of PV and ET surgeries was complicated by vascular occlusion (7.7%) or by a major hemorrhage (7.3%). Prospective investigations analyzing the optimal prophylaxis in these patients are suggested.

Clinical significance of different antiphospholipid antibodies in the WAPS (warfarin in the antiphospholipid syndrome) study

To assess the clinical significance of lupus anticoagulants (LAs) and antiphospholipid antibodies (aPLs) toward thrombosis and abortions, we measured them in 112 patients whose samples were available at enrollment in the warfarin in the antiphospholipid syndrome (WAPS) study. Enzyme-linked immunosorbent assay (ELISA) and coagulation test values in the highest and lowest tertiles were compared. When considered separately, IgG antibodies to β2-glycoprotein I (aβ2GPI) and prothrombin (aPT) were associated with anamnestic arterial and venous thrombosis, respectively, and those to annexin AV (aAnAV) with abortions. IgM antibodies to protein S and the lupus ratio of the dilute prothrombin time were associated with prospective thrombosis. No other association for IgM antibodies was seen. LA-positive patients who carried aβ2GPI antibodies were at risk of anamnestic arterial and total thrombosis and aPT antibodies to that of anamnestic venous and total thrombosis. LA-positive patients who carried IgG aβ2GPI and aAnAV antibodies were at risk for both anamnestic abortion and prospective thrombosis. Overall, these data support the inclusion of aβ2GPI antibodies in and suggest the removal of anticardiolipin antibodies from the laboratory criteria of the antiphospholipid syndrome. They also suggest that the measurement of aPT and aAnAV antibodies is useful in some selected situations and that there is little role for IgM antibody detection.

Proposals and rationale for revision of the World Health Organization diagnostic criteria for polycythemia vera, essential thrombocythemia, and primary myelofibrosis: recommendations from an ad hoc international expert panel

The Janus kinase 2 mutation, JAK2617V>F, is myeloid neoplasm-specific; its presence excludes secondary polycythemia, thrombocytosis, or bone marrow fibrosis from other causes. Furthermore, JAK2617V>F or a JAK2 exon 12 mutation is present in virtually all patients with polycythemia vera (PV), whereas JAK2617V>F also occurs in approximately half of patients with essential thrombocythemia (ET) or primary myelofibrosis (PMF). Therefore, JAK2 mutation screening holds the promise of a decisive diagnostic test in PV while being complementary to histology for the diagnosis of ET and PMF; the combination of molecular testing and histologic review should also facilitate diagnosis of ET associated with borderline thrombocytosis. Accordingly, revision of the current World Health Organization (WHO) diagnostic criteria for PV, ET, and PMF is warranted; JAK2 mutation analysis should be listed as a major criterion for PV diagnosis, and the platelet count threshold for ET diagnosis can be lowered from 600 to 450 x 10(9)/L. The current document was prepared by an international expert panel of pathologists and clinical investigators in myeloproliferative disorders; it was subsequently presented to members of the Clinical Advisory Committee for the revision of the WHO Classification of Myeloid Neoplasms, who endorsed the document and recommended its adoption by the WHO.

Therapy for Polycythemia Vera and Essential Thrombocythemia Is Driven by the Cardiovascular Risk

The clinical course of polycythemia vera (PV) and essential thrombocythemia (ET) is characterized by an increased incidence of thrombotic and hemorrhagic complications and an inherent tendency to progress into myelofibrosis or acute myeloid leukemia. Major predictors of vascular events are increasing age and previous thrombosis. Myelosuppressive drugs can reduce the rate of thromboses and hemorrhages, but there is concern that their use accelerates the rate of leukemic transformation. Thus, a risk-oriented management strategy is recommended. Low-risk patients with PV should be treated with phlebotomy and low-dose aspirin, whereas those with ET can be left untreated. Cytotoxic agents are recommended in high-risk cases and hydroxyurea is the drug of choice in most patients. Interferon alpha or anagrelide could be considered in selected young patients or as second-line therapy in those refractory or intolerant of hydroxyurea. The recent identification of JAK2V617F mutation in a substantial proportion of patients with PV and ET raises new questions regarding both risk classification and management, but additional studies on these issues are required.

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.

How I treat patients with polycythemia vera

The clinical course of polycythemia vera (PV) is marked by a high incidence of thrombotic complications; fibrotic and leukemic disease transformations are additional causes of morbidity and mortality. Major predictors of vascular events are increasing age and previous thrombosis; leukocytosis and high JAK2 V617F allele burden are currently being investigated for additional prognostic value in this regard. Myelosuppressive drugs can reduce the rate of thrombosis, but there is concern that their use raises the risk of transformation into acute leukemia. 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, and the drug of choice is hydroxyurea because of its efficacy in preventing thrombosis and low leukemogenicity. Interferon-alpha should be reserved for selected categories of patients due to high cost and toxicity. The demonstration of JAK2 V617F mutation in the vast majority of PV patients opens the avenue for the development of promising new molecularly targeted drugs.

The paradox of platelet activation and impaired function: platelet-von Willebrand factor interactions, and the etiology of thrombotic and hemorrhagic manifestations in essential thrombocythemia and polycythemia vera

Patients with essential thrombocythemia (ET) and polycythemia vera (PV), complicated by microvascular ischemic or thrombotic events, have shortened platelet survival, increased beta-thromboglobulin, platelet factor 4, and thrombomodulin levels, and increased urinary thromboxane B2 excretion. These are all reversible by inhibition of platelet cyclooxygenase 1 with aspirin, and are therefore indicative of platelet activation and platelet-mediated thrombotic processes. The thrombotic tendency persists as long as platelet counts are above the upper limit of normal (400 x 10 (9)/L). Despite strong evidence of in vivo platelet activation, the ex vivo platelet function tests are impaired. Platelet dysfunction in ET and PV typically is characterized by a missing second-wave adrenaline aggregation, an increased adenosine diphosphate aggregation threshold, and reduced secretion products, but a normal arachidonic acid or collagen-induced aggregation. The proposed concept is that platelets in thrombocythemia (ET and PV) are hypersensitive. Due to the existing high shear stress in the microvasculature (end-arterial circulation), platelets spontaneously activate, secrete their products, form aggregates mediated by von Willebrand factor (vWF) that transiently plug the microcirculation, deaggregate, and then recirculate as exhausted defective platelets with secondary storage pool disease on ex vivo analysis. At increasing platelet counts from below to above 1000 x 10 (9)/L, the thrombotic condition changes into an overt spontaneous bleeding tendency as a result of a functional vWF deficiency that is caused by proteolysis of large vWF multimers. This is consistent with acquired type 2 von Willebrand syndrome (AvWS). AvWS is reversible by reduction of the platelet count to normal. The acquired JAK2 V617F gain of function mutation is the cause of trilinear myeloproliferative disease with the sequential occurrence of ET and PV. Heterozygous JAK2 V617F mutation with slightly increased kinase activity is enough for the induction of spontaneous megakaryopoiesis and erythropoiesis, and an increase of hypersensitive platelets is the cause of aspirin-sensitive, platelet-mediated microvascular ischemic and thrombotic complications in ET and early PV mimicking ET. Homozygous JAK2 mutation with pronounced increase of kinase activity is associated with pronounced trilinear megakaryocyte, erythroid, and granulocytic myeloproliferation, with the most frequent clinical picture of classical PV complicated by major thrombosis, in addition to the platelet-mediated microvascular thrombotic syndrome of thrombocythemia.

Risk of thrombosis in patients with essential thrombocythemia and polycythemia vera according to JAK2 V617F mutation status

We compared the laboratory and clinical findings of 179 patients with essential thrombocythemia (ET) and 77 with polycythemia vera (PV) classified according to the presence of the JAK2 V617F mutation. A gradient was observed in laboratory values between patients with JAK2 wild-type ET, JAK2 V617F ET and PV (all of whom carried the JAK2 mutation). The rate of thrombotic complications in JAK2-positive ET patients was significantly higher than that in wild-type ET patients and not statistically different from that in PV patients.