High-dose hydroxyurea in the treatment of poor-risk myeloid leukemias.

The aim of the study was to evaluate the antileukemic effectiveness and toxicity of high-dose hydroxyurea (HHY) and to assess its acute toxicity. Between August 1997 and October 1998, 12 consecutive adult patients (>18 years) with high-risk acute myeloid leukemia (AML) (four patients in first early relapse, seven patients with secondary AML, and one patient with de novo AML concomitant to a lymphoproliferative disorder) were enrolled to receive a single course of HY (100 mg/kg per day) until bone marrow aplasia or for a maximum of 30 days. Of the 12 patients, 5 (41.6%) achieved complete remission (CR), 1 achieved partial remission (PR), 4 were resistant to treatment, and 2 died during induction from infection. No patient with relapsed AML achieved CR, while it was achieved by five of eight patients with secondary AML at diagnosis; five of six MDR1+ patients achieved CR. As concerns follow-up of the CR patients, one did not receive any further treatment and died in CR from pulmonary aspergillosis, and one with a concomitant chronic lymphocytic leukemia (CLL) received two courses of FLAG (fludarabine, cytarabine, granulocyte colony-stimulating factor) regimen with disappearance of the clonal Ig rearrangement, but relapsed after 11 months and died from pneumonia. The remaining three patients were consolidated with two courses of high-dose cytosine arabinoside (AraC), followed by peripheral blood stem cell transplantation (PBSCT) in one patient. One of them relapsed after 3 months, while the other two are still in continuous complete remission (CCR) after 16 and 28 months, respectively. This study has demonstrated the safety and efficacy of HHY in inducing CR in AML patients with unfavorable prognosis. Despite the small number of patients, these encouraging results warrant further studies.