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Polycythemia vera is a clonal disorder of hematopoietic stem/progenitor cells. It manifests as an expansion of red cell mass. It is the most common chronic myeloproliferative neoplasm. In virtually all cases, it is characterized by a V617F point mutation in JAK2 exon 14 or less common mutations in exon 12. The landmark discovery of the autonomously activated JAK/STAT signaling pathway paved the way for the clinical development of the first target drug, the JAK1 and JAK2 inhibitor ruxolitinib. This is now approved for patients with resistance or intolerance to hydroxyurea. Phlebotomies and hydroxyurea are still the cornerstone of treatment, and aim to prevent the first appearance or recurrence of cardiovascular events that, together with progression to post-polycythemia vera myelofibrosis and leukemia, represent the main causes of death. Interferon-α is an alternative drug and has been shown to induce molecular remissions. It is currently undergoing phase III trials that might eventually lead to its approval for clinical use. The last few years have witnessed important advances towards an accurate early diagnosis of polycythemia vera, greater understanding of its pathogenesis, and improved patient management. This review will focus on the most recent achievements and will aim to unify the different concepts involved in a personalized approach to the patient with polycythemia vera. In spite of many recent advances in the understanding of its pathogenesis and improved disease management, polycythemia vera remains a life-threatening myeloproliferative neoplasm for which there is no cure. This review will present a critical overview of evolving concepts in diagnosis and treatment of this disease., (Copyright© Ferrata Storti Foundation.)

Hematocrit control below 45% is associated with a lower rate of thrombosis in polycythemia vera. In patients receiving hydroxyurea, this target can be achieved with hydroxyurea alone or with the combination of hydroxyurea plus phlebotomies. However, the clinical implications of phlebotomy requirement under hydroxyurea therapy are unknown. The aim of this study was to evaluate the need for additional phlebotomies during the first five years of hydroxyurea therapy in 533 patients with polycythemia vera. Patients requiring 3 or more phlebotomies per year (n=85, 16%) showed a worse hematocrit control than those requiring 2 or less phlebotomies per year (n=448, 84%). There were no significant differences between the two study groups regarding leukocyte and platelet counts. Patients requiring 3 or more phlebotomies per year received significantly higher doses of hydroxyurea than the remaining patients. A significant higher rate of thrombosis was found in patients treated with hydroxyurea plus 3 or more phlebotomies per year compared to hydroxyurea with 0-2 phlebotomies per year (20.5% vs. 5.3% at 3 years; P<0.0001). In multivariate analysis, independent risk factors for thrombosis were phlebotomy dependency (HR: 3.3, 95%CI: 1.5-6.9; P=0.002) and thrombosis at diagnosis (HR: 4.7, 95%CI: 2.3-9.8; P<0.0001). The proportion of patients fulfilling the European LeukemiaNet criteria of resistance/intolerance to hydroxyurea was significantly higher in the group requiring 3 or more phlebotomies per year (18.7% vs. 7.1%; P=0.001) mainly due to extrahematologic toxicity. In conclusion, phlebotomy requirement under hydroxyurea therapy identifies a subset of patients with increased proliferation of polycythemia vera and higher risk of thrombosis., (Copyright© Ferrata Storti Foundation.)

We tested the hypothesis that levels of pentraxin high sensitivity C-reactive protein and pentraxin 3 might be correlated with cardiovascular complications in patients with essential thrombocythemia and polycythemia vera. High sensitivity C-reactive protein and pentraxin 3 were measured in 244 consecutive essential thrombocythemia and polycythemia vera patients in whom, after a median follow up of 5.3 years (range 0-24), 68 cardiovascular events were diagnosed. The highest C-reactive protein tertile was compared with the lowest (>3 vs. <1 mg/L) and correlated with age (P=0.001), phenotype (polycythemia vera vs. essential thrombocythemia, P=0.006), cardiovascular risk factors (P=0.012) and JAK2V617F allele burden greater than 50% (P=0.003). Major thrombosis rate was higher in the highest C-reactive protein tertile (P=0.01) and lower at the highest pentraxin 3 levels (P=0.045). These associations remained significant in multivariate analyses and indicate that blood levels of high sensitivity C-reactive protein and petraxin 3 independently and in opposite ways modulate the intrinsic risk of cardiovascular events in patients with myeloproliferative disorders.

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.

Background and Objectives: Polycythemia vera (PV) is rare in women of childbearing age with only 20 previous pregnancies reported., Design and Methods: We report a series of 18 pregnancies (19 fetuses) in eight women with PV managed prior to or following implementation of management guidelines tailored to PV in pregnancy, and review the literature., Results: Seven of these pregnancies were managed by standard antenatal care (group A) without specific attention to the women's PV. All remaining 11 pregnancies (group B) were managed following a formal protocol and received tailored management principally comprising tight control of the hematocrit by venesection, and the use of interferon ? in three patients, in addition to aspirin 75 mg, and prophylactic low molecular weight heparin (LMWH). Each pregnancy was monitored with uterine artery Doppler examinations and regular fetal scanning. In group A (n=7) there was one live birth, which required delivery at 34 weeks due to placental insufficiency, three first trimester miscarriages, two stillbirths and one combined stillbirth and neonatal death (twins) associated with placental dysfunction. All 11 patients in group B received aspirin and post-partum LMWH; four also received venesection (during pregnancy), three interferon-a and three antenatal LMWH. There were ten live births, nine at term, one first trimester miscarriage and no intrauterine growth retardation., Interpretation and Conclusions: Pregnancy in PV without meticulous attention to hematocrit is associated with poor fetal outcome. Aggressive intervention with control of hematocrit, aspirin and some LMWH appears to be associated with significantly better outcome (p=0.0017).

Background and Objective: Current guidelines for the management of patients with polycythemia vera (PV) derive from a few clinical trials and several uncontrolled clinical studies. The purpose of this paper is to critically review the available evidence in literature for selecting the best treatment in the single patient., Methods: The authors have been working in this field contributing original papers whose data have been used for this study. In addition, the material analyzed in this article includes papers published in the journals covered by the Science Citation index and Medline., Results: Therapeutic strategies for patients with PV include both cytoreductive and antithrombotic drugs. Among cytoreductive treatments, phlebotomy is associated with poor compliance and an increased incidence of thrombosis in the first three-five years, whereas chemotherapy may induce an higher risk of secondary malignancies after seven-ten years of follow-up. New cytoreductive drugs virtually devoid of mutagenic risk include alpha-interferon and anagrelide, but their role in reducing thrombotic complications or mortality remains to be demonstrated. Antithrombotic drugs, such as aspirin, are frequently used in PV, despite doubts regarding safety and efficacy., Conclusions: The management of patients with PV is a difficult balance between the prevention of thrombotic complications and the risk of drug side effects and toxicity. Appropriate studies are needed and an European collaboration has been set up for launching a randomized, placebo-controlled clinical trial (European Collaboration on Low-Dose Aspirin-ECLAP study) aimed at testing the efficacy of low-dose aspirin in preventing thrombosis and prolonging survival in PV patients.

Polycythemia and hyperhomocysteinemia are risk factors for thrombosis. Since red blood cells actively metabolize methionine to homocysteine, we investigated whether or not patients with polycythemia have increased plasma levels of homocysteine, which might contribute to their increased thrombotic risk. In ten patients with polycythemia, the plasma homocysteine levels were measured before phlebotomy, three days after the procedure and 1-2 months later. The baseline mean plasma homocysteine levels in patients (9.7 +/- 1.6 mumol/L [+/-SD]) did not differ significantly from that found in 30 sex- and age-matched healthy controls (12.2 +/- 6.9). Despite a fall in the patients' mean [+/-SD] hematocrit from 0.50 +/- 0.02 at baseline to 0.47 +/- 0.03 three days after phlebotomy (significant at 95%) and to 0.48 +/- 0.02 after 1 to 2 months (not significant), the mean plasma homocysteine levels did not change significantly (9.9 +/- 2.3 mumol/L at 3 days and 9.7 +/- 2.1 mumol/L at 1-2 months). It is unlikely that high plasma homocysteine levels contribute to the increased thrombotic risk of polycythemic patients.

Background and Methods: Polycythemia vera (PV) and essential thrombocythemia (ET) in young patients are rarely reported. Their natural histories seem to differ from those of older patients and the best treatment is still uncertain. In this follow-up study we have evaluated a cohort of 64 consecutive patients younger than 40 to determine the incidence of thrombohemorrhagic events and the long-term outcome., Results: Twenty-eight patients (20 M; 8 F) had PV, and 36 ET (21 F, 15 M). Mean follow-up was 8.2 years (range 4 months-16.7 years) in PV and 6.5 years (range 5 months-15 years) in ET. Thrombohemorrhagic symptoms were present at diagnosis in 10/28 patients (35%) with PV and in 12/36 patients (33%) with ET; during follow-up in 15/28 PV patients (53%) and in 13/36 ET patients (36%). Thrombotic events were the most frequent symptoms, both at diagnosis (52% in PV, 65% in ET) and during follow-up (43% in PV, 52% in ET). A total of 19/28 PV patients (67%) and 17/36 ET patients (47%) had thrombotic complications. Hemorrhagic complications at diagnosis were 4% and during follow-up 13% in PV, and 15% and 13% in ET. A total of 5/28 (18%) PV and 6/36 (17%) ET patients had hemorrhagic events. No laboratory parameter, including platelet count, was predictive of these events. Five PV patients had major thrombotic complications (18%). Four PV patients died (14%), 2 because of ANLL (7%), 2 because of thrombotic events (7%). Four ET patients experienced major complications, in three cases thrombotic (8.3%), in one hemorrhagic. No leukemic transformation occurred in ET and no ET patient died., Conclusions: In our experience, severe thrombohemorrhagic complications are present in young patients with PV and ET, which excludes young age as a favorable prognostic factor. Treatment also seems advisable for young patients and myelosuppressive treatment might be required. Prospective studies are urgently needed to assess the best treatment for this particular subset of patients.