What is chronic myeloid leukemia (CML)?
Chronic myeloid leukemia (CML) is a slow-developing cancer of the bone marrow in which immature cells called “blasts” overtake the healthy bone marrow. Patients with CML have an abnormal chromosome in their blood cells called the Philadelphia chromosome. No one is born with the Philadelphia chromosome; rather it is a result of a genetic accident that happens in a blood-forming stem cell in the bone marrow. It is actually a combination of 2 chromosomes (chromosomes 9 and 22) that become abnormally fused. This fusion results in the creation of a new gene called BCR-ABL.
Chronic myeloid leukemia is classified as a myeloproliferative neoplasm. These are slow growing types of leukemia which result in overproduction of white blood cells by the bone marrow, causing high blood counts.
Chronic myeloid leukemia (CML) may also be referred to as chronic myelogenous leukemia, chronic myelocytic leukemia or chronic granulocytic leukemia.
Unlike acute myeloid leukemia (AML), CML takes longer to develop. Most people can live with CML for many years. Rarely CML can also turn into acute leukemia, which needs immediate medical attention. It is also important to know that some patients with acute leukemia (especially acute lymphocytic leukemia) have the Philadelphia chromosome, but do not have CML. Treatment is different, though some strategies overlap for CML and ALL with the Philadelphia chromosome.
Chronic myeloid leukemia (CML) has three phases:
- Chronic phase
- Accelerated phase
- Blast phase
Most patients with CML are diagnosed in the chronic phase of disease, when they have only a small number of immature cells (blasts) in the blood or bone marrow. Often they only find out they have the disease because blood counts were checked and found to be abnormal. In accelerated and blast phase disease, the number of immature cells increase, and patients typically experience more symptoms.
People with CML have either the Philadelphia chromosome, or the gene made by the Philadelphia chromosome called Bcr-Abl. When you are diagnosed, your physicians will request testing to find out if you have the Philadelphia chromosome or Bcr-Abl. New, targeted treatments have been developed to treat these chromosomal abnormalities.