Chronic myeloid leukemia (CML) normally progresses from the chronic phase to an accelerated phase and ultimately into a blastic or acute leukemia phase over a period of several years.
The diagnosis of blastic phase requires at least one of the following:
- Persistent presence of 30 percent or more myeloblasts in marrow or peripheral blood
- Tumor nodules outside the bone marrow or spleen
The diagnosis of the blastic phase requires greater than 30 percent myeloblasts in marrow or blood. Patients in blastic phase live an average of 3 to 6 months.
Treatment of Blastic Phase CML
When CML progresses to the blastic phase, the leukemia cells may look like either myeloid or lymphoid cells and generally respond poorly to treatment. Until recently, intensive chemotherapy regimens were used for the treatment of CML, including high-dose Cytosar® (cytarabine) and Cerubidine® (daunorubicin). They can induce remissions in 25 percent to 35 percent of patients in the blast phase.
Patients with a lymphoid blast phase who were treated with therapy similar to that given for acute lymphoid leukemia (Oncovin® (vincristine), Adriamycin® (doxorubicin), cyclophosphamide, and dexamethasone) had a complete remission rate of 60 percent. However, all remissions achieved with chemotherapy in blast phase were of relatively short duration. In 2001, Gleevec® (imatinib mesylate) was approved for the treatment of recurrent CML. CML blastic phase is now often treated with a combination of imatinib plus chemotherapy.
Allogeneic stem cell transplantation - Selected patients in the blastic phase treated with high-dose chemotherapy and allogeneic stem cell transplant using stem cells from a related donor have a 5-year survival of approximately 15 percent. There has been significant recent progress in the selection of compatible unrelated stem cell donors. Patients in blastic phase CML transplanted from an HLA-compatible unrelated donor have a 10 percent probability of 5-year survival.
Strategies to Improve Treatment
Researchers are currently investigating new treatments for CML. Participation in trials of these treatments will lead to improved therapies. If you wish to participate in a clinical trial, please talk to your doctor about the potential benefits and side effects of the treatment.
Clinical trials - New TKIs and chemotherapy drugs continue to be developed and evaluated in clinical trials for patients with recurrent cancers. The purpose of these trials is to evaluate new drugs for best dosage, safety, and effectiveness.
This content was last reviewed
August 15, 2010 by Dr. Reshma L. Mahtani.