Chronic myelogenous leukemia (CML) is an uncommon cancer that affects the blood and bone marrow. It happens when the spongy material inside some bones (bone marrow) makes too many immature white blood cells, or blasts. These cells can’t do their job correctly and crowd out healthy blood cells that help fight infection and make red blood cells and platelets. CML can start at any age but is more common in older adults. It tends to progress slowly over years and may be caught during tests for another health problem.
It’s important to know that there are 3 phases of chronic myelogenous leukemia. The phase a patient is in determines how likely the leukemia is to respond to treatment. During chronic phase, there are usually fewer than 10 percent blasts in the blood and bone marrow. This phase can last a few months or up to several years.
During accelerated phase, blasts plus promyelocytes (immature white blood cells) increase to 30 percent or more of the bone marrow cells. This is the most dangerous phase of chronic myelogenous leukemia and requires more aggressive treatment.
The leukemia cells have a specific type of genetic change called the Philadelphia chromosome. In people with this change, sections of chromosomes 9 and 22 swap places. This makes the resulting chromosome abnormal and allows cancer cells to grow out of control. The change isn’t passed from parent to child, and it doesn’t happen because of a person’s environment or lifestyle. It’s also not related to a person’s race or ethnicity.
In a few cases, the change in the genes responsible for making BCR-ABL is caused by a mistake during cell division. It’s not known exactly what causes this to happen. In most cases, however, the change is due to something that happened during a person’s lifetime.
Symptoms of chronic myelogenous leukemia include tiredness, weight loss and fever. Infections are common, and swollen lymph nodes in the arms, groin, chest and neck are also often seen. People with this disease may also have easy bruising and bleeding because their bone marrow can’t make enough platelets.
A doctor can diagnose CML based on symptoms, medical history and laboratory tests. A bone marrow biopsy is also used to diagnose the disease.
The main treatments for CML are chemotherapy and a stem cell transplant. Chemotherapy uses drugs to kill the unhealthy cells in your blood and bone marrow. Then, healthy blood-forming cells are transplanted into your body to replace the unhealthy ones. A transplant can be from a family member, unrelated donor or umbilical cord blood. In addition to treatment, patients should also consider participating in a clinical trial. These trials test new types of treatment and their effectiveness. They may also be less invasive than some traditional therapies. This PDQ cancer information summary was written by experts at the National Cancer Institute (NCI) and the American Society of Hematology (ASH). It is reviewed regularly and updated as necessary.