Management of patients with essential thrombocythemia: current concepts and perspectives.

Essential thrombocythemia must now be regarded as a heterogeneous disease. Recent availability of clonality studies have repeatedly shown that a significant number of female patients diagnosed as E.T. according the most stringent criteria had a definitely polyclonal myelopoiesis. Although the incidence of patients newly diagnosed every year is low, there is in fact a conspicuous population of E.T., followed as outpatients in every department of hematology or internal medicine, including a large number of young females. These eventualities should be integrated in further discussions of the benefit/risk ratio of cytoreduction with the presently available drugs. The combination of several evidence-based data is the basis of a widely accepted stratification of high-risk patients defined by any of the following features. Age > 60 to 65. History of thrombosis or embolic or major ischemic events. Platelet counts in excess of 1000 or 1500 x 10(9)/L. In the question of chemotherapy in E.T., growing concern comes from the potential leukemogenic risk associated with the presently available drugs and extends beyond Melphalan, Busulfan and other alkylating agents and includes non-alkylating agents like Hydroxyurea. At the same time, much attention has been paid to the introduction of very precise initial diagnostic criteria directed to elimination of other myeloproliferative or myelodysplastic disorders with an increased risk of transformation. Present treatment of E.T. is a compromise between prevention of E.T. related thrombotic and bleeding complications on one hand and long term side effects and toxicity of the presently available drugs on the other hand. The recent availability of non mutagenic drugs like Interferon and most of all Anagrelide; the recognition of the role of antiaggregating agents in the treatment of platelet related microvascular ischemic events gives the opportunity for further comparative prospective trials. The use of aspirin in the management of pregnant E.T. patients is now widely accepted but there is still controversies concerning the use of Interferon in this situation.