Efficacy and safety of hydroxyurea in patients with essential thrombocythemia.

Hydroxy-urea has emerged as the treatment of choice in patients with essential thrombocythemia and an high risk of thrombosis because of its efficacy and only rare acute toxicity. However, there is some concern regarding the potential role of this drug in enhancing the risk of leukemic transformation. This risk suggests not to use hydroxyurea in young patients at low-risk for thrombosis. In these cases, major or fatal vascular occlusive complications are rare, and no data are available on the effectiveness of HU in reducing this rate. Sequential multiple chemotherapy, such busulphan followed by HU, should be avoided in any case because of the high risk of secondary leukemias.