A phase II pilot trial of high-dose hydroxyurea in chronic myelogenous leukemia.

Suppression or eradication of the Philadelphia (Ph1) chromosome has been a major goal in the therapy of chronic myelogenous leukemia (CML). Variable levels of Ph1 chromosome negativity have been achieved using interferon-alfa, busulfan, combination chemotherapy, and allogeneic bone marrow transplantation. This study evaluated the effect of achieving a predetermined level of myelosuppression using hydroxyurea on bone marrow cytogenetics in CML. Fourteen patients with chronic phase CML received 25 cycles of therapy. Fourteen of the 25 cycles were associated with cytogenetic responses consisting of 25% or more Ph1 negative metaphases (range, 25% to 100%). Nine of the responses consisted of 50% or greater Ph1 negative metaphases. Toxicity was exclusively due to consequences of myelosuppression, including febrile neutropenia and thrombocytopenia. In chronic phase CML, hydroxyurea induces cytogenetic responses with tolerable toxicity and is an attractive agent for further study as a component of treatment strategies aimed at eradicating the Ph1 + population in CML.