Leukemia and myelodysplasia effect of multiple cytotoxic therapy in essential thrombocythemia

Essential thrombocythemia (ET) is a chronic myeloproliferative disorder characterized by increased risk of thrombosis and/or hemorrhages. Cytotoxic drugs are mostly used in patients at high risk for thrombotic complications, while their use is still debated in low risk patients because of the risk of leukemia or secondary neoplasm. We discuss the leukemic risk of available treatment strategies in a large cohort of patients. Over a 12 years period we treated 23 patients with busulfan (BU), 1 with pipobroman (Pi), 6 with 32P, 48 with hydroxyurea (HU) in 62 cases associated with acetyl salicylic acid (ASA) while 77 patients received ASA alone and 33 did not receive any therapy. We observed 2 cases of acute leukemia (AL) and 1 of myelodysplastic syndrome (MDS). One of these patients had been treated with 32P and Pi these after with and the other two with BU and HU. They represented 23% of all patients treated with more than 1 cytotoxic agent, 16.6% of 32P treated subjects, 4% of those with HU and 6.4% of those with BU. The case of MDS occurred in a 81 years old female and represents 4% of cases of ET over the 70 years of age. No cases of AL or MDS were observed in patients not receiving cytotoxic therapy (with or without ASA). According to our experience the use of more than one cytotoxic agent in ET confirms the increase in the risk of leukemia in these cases. However, none of the patients treated with HU alone, even for more than 10 years (12 cases) developed AL. No treatment or therapy with ASA alone may be the best choice in young patients with ET with a low risk of thrombotic complications.