CML, a malignant disorder of stem cells, is characterized by increases in both immature and mature myeloid, erythroid, and lymphoid cells, as well as platelets in the peripheral blood. The cytogenetic hallmark of CML is the Philadelphia(Ph)chromosome found in the malignant cells of 95% of patients. CML comprises 7-20% of all leukemias with an overall incidence in the general population estimated at 1 to 2 per 100,000. The peak incidence occurs in the fifth decade, however, all age groups, including children, are affected. The only reported environmental risk factor is exposure to excessive ionizing radiation that is documented in only a very small percentage of patients. Clinically, CML is characterized by an initial chronic phase in which patients may report mild constitutional symptoms; however, 40-50% are asymptomatic and are diagnosed based upon abnormal blood counts discovered during a routine examination. The chronic phase typically lasts three to five years, and is followed by an accelerated phase distinguished by progressive systemic symptoms, an increasing resistance to conventional chemotherapy, and a rise in the peripheral blood and bone marrow blast count. This evolves rapidly into a blastic crisis characterized by immature cells resembling the blasts characteristic of acute leukemia. The presence of 30% or more blastic cells in the blood or marrow is diagnostic of this final blastic phase which is typically fatal within 3 to 6 months.

The primary treatment options for CML have traditionally been monotherapy with either busulfan or hydroxyurea. Both agents are able to control the clinical symptoms associated with CML, as well as induce hematological remissions in 80% of chronic phase patients. However, complete cytogenetic remissions with either agent are rare, and neither is able to prevent eventual progression to the terminal blastic phase; therefore, these therapies can only be considered palliative.

The primary purpose of this clinical research trial is to study the feasibility of a reduced intensity allogenic transplant for CML. This study will also determine the side effects as well as the response rate.