The management of 'low-risk' and 'intermediate-risk' patients with primary thrombocythaemia. MPD (UK) Study Group

Essential thrombocythaemia: challenges and evidence-based management

Essential thrombocythaemia was first described over 70 years ago. This condition is dominated by thrombotic and haemorrhagic complications and, in the long-term, by risk of transformation to myelofibrosis and/or acute leukaemia. However, it is heterogeneous both clinically and biologically. Here, a review of current concepts in disease aetiology and management is offered with reference to recent focused reviews where appropriate. In addition, five specific areas are discussed in detail: the role of the trephine biopsy, the disease entity prefibrotic myelofibrosis; the recently described Janus kinase 2 (JAK2) mutations; the leukaemogenicity of hydroxyurea (hydroxycarbamide); and lastly, the implications of the results of the Medical Research Council Primary Thrombocythaemia 1 study are explored.

Management of polycythemia vera and essential thrombocythemia

The optimal management of patients with polycythemia vera (PV) and essential thrombocythemia (ET) continues to be controversial. Both diseases present diagnostic challenges and there is a paucity of data from randomized clinical trials to guide therapeutic decisions. However, the past two years have seen major advances in our understanding of these myeloproliferative disorders (MPD). First, the ECLAP study demonstrated the anti-thrombotic efficacy of aspirin in patients with PV. Second, the PT-1 trial, the largest randomized study of any MPD, has provided much needed guidance on the optimal management of patients with ET. Third, the identification of a single JAK2 mutation in most patients with PV, and in some of those with ET, illuminates the pathogenesis of these diseases and raises questions about the boundary between them. For the purpose of management decisions, it remains appropriate to consider them as separate entities for the time being. However, as we learn more about the clinical significance of the JAK2 mutation, it seems likely that the coming years will see major changes in the way we classify and manage these disorders.

Essential thrombocythemia

Essential thrombocythemia is a distinct clinical entity within the spectrum of myeloproliferative disorders. There is as yet no pathognomonic diagnostic test, and patients who currently fall into the category of essential thrombocythemia are likely to be heterogeneous. This article discusses diagnostic criteria, clinical features, prognosis, and management.

Sticky platelet syndrome and thrombocythemia

Platelets are intimately involved in the pathogenesis of thromboembolic disorders, especially arterial forms of thrombosis. Although most arterial thromboses develop on the basis of endothelial injuries, some do not. In these instances "hyperactive" platelets could be the cause. Hyperaggregable platelets have been described in association with a number of acquired disease entities whereby the cause-and-effect relationship is unclear. In contrast, the sticky platelet syndrome is a congenital, autosomal dominant disorder, characterized by hyperaggregable platelets in response to ADP, epinephrine, or both. Patients usually seek treatment for transient or permanent arterial vascular occlusions. These are often precipitated by stressful events. Treatment with low-dose aspirin (81 mg/day) reverses clinical symptoms and hyperaggregability in the laboratory.

Current treatment practice for essential thrombocythaemia in adults

Essential thrombocythaemia (ET) is a relatively benign chronic myeloproliferative disorder that occurs primarily in middle-aged patients. Its clinical course is characterised by thomboembolic and, less frequently, by haemorrhagic complications. Life expectancy of ET is generally of normal length and progression to acute leukaemia is a rare event. About one third of all patients are asymptomatic at diagnosis and many of them remain without complications for years. Therefore, the main challenge for treating patients with ET is to select patients who will benefit from a cytoreductive or antiplatelet therapy, because it is doubtful whether the beneficial effects of therapy outweigh the potential hazards in all cases. For this reason a risk stratification in high and low risk ET patients is essential. The treatment of ET has evolved from alkylating agents to hydroxyurea (HU) or pipobroman and more recently to agents such as IFN-alpha and anagrelide. Aspirin as an antiplatelet therapy is also expected to play a part in the treatment of ET. HU is first-line therapy for elderly patients with high risk ET. In young ET patients without ET related complications and a platelet count << 1000 - 1500 x 10(9)/l abstention from cytoreductive therapy or therapy with low-dose aspirin alone seems to be appropriate. The aim of this review is to address the current treatment practice for ET in adults.