What is Chronic Myelogenous Leukemia?
Chronic myelogenous leukemia (CML) is a condition in which the body produces too many white blood cells, which eventually build up and and get in the way of healthy blood cells doing their work. In CML, the white blood cell are abnormal cells that do not grow the way they are supposed to or shut down when they are supposed to.
CML is not that common; only 5-10% of leukemias in children and adolescents are diagnosed as CML.
CML begins in the blood marrow, where blood cells are made. The cells that would normally become white blood cells grow into leukemia cells instead. CML goes through 3 phases: chronic, accelerated, and blast. In the chronic phase, tests find mostly the mature CML cells in the blood. In later phases, tests will find younger cells, called blast cells, that have not fully developed yet, which means the body is producing more CML cells than before.
Approximately 85% of patients are diagnosed in the chronic phase and then progress to the accelerated and blast phases after 3-5 years.
The signs and symptoms vary as CML progresses:
- In the chronic stage, signs and symptoms include fatigue, fever, and an enlarged liver and spleen.
- In the progressive phases, signs and symptoms include bleeding, anemia and generalized pain.
Our approach to Chronic Myelogenous Leukemia
The diagnosis of CML is based on the following:
- Blood tests that show an elevated WBC count
- Tests of tissue (called histopathology), including bone marrow and other blood cells for signs of CML
- The presence of a specific chromosome called the Philadelphia (Ph) chromosome in bone marrow cells. This is a common mutation that happens in patients with CML.
The appropriate course of therapy is decided based on what stage the patient’s CML is in, and how much risk it poses to the patient. The factors we consider include age, spleen size, blood tests to tell us how advanced the CML is, and the presence or absence of the Ph chromosome.
The main goal of CML treatment is to achieve remission, which means getting the blood cell counts back to normal and to no longer being able to detect the presence of the Ph chromosome or the mutation that causes it. Although a variety of medications have been used in CML, including medicines that affect blood cell development and immune system function, the current medicine of choice is imatinib mesylate. This medicine is called a targeted therapy, and it prevents the development of cells with the Ph mutation, without having much effect on other cells.
If imatinib or other similar medicines do not effectively get patients to remission, a procedure called allogeneic stem cell transplantation (SCT) remains the only proven cure for CML. Ideally, SCT should be performed in the chronic phase for patients who have not achieved remission on targeted medicines.