Chronic myeloid leukemia (CML)

Chronic myeloid leukemia (CML) is a slow-developing cancer of the tissue inside your bones, called bone marrow. This type of blood cancer causes your bone marrow to make too many immature white blood cells. Over time, this can cause symptoms like fatigue and anemia. CML is also known as chronic myelogenous leukemia.

Advances in CML treatments have allowed many people to reach remission and live symptom-free. Penn Medicine’s large multispecialty blood cancer care teams include hematologists, medical oncologists, and other specialists who have expertise in every type of leukemia, including CML. Using the latest diagnostic tests and treatments, we can provide an accurate and precise diagnosis and a care plan designed around you.

Chronic forms of leukemia, like CML, develop over a longer period, often taking months or years before symptoms develop. Acute leukemia types, like acute myeloid leukemia (AML), progress quickly and are more aggressive. Rarely, CML can develop into an acute form of leukemia.

CML is often found during a routine blood test before symptoms develop. If you begin showing signs of the disease, symptoms are mild at first and get worse over time. They can include:

• Fatigue
• Shortness of breath
• Night sweats
• Fever
• Loss of appetite and unexplained weight loss
• An enlarged spleen that causes a feeling of fullness or discomfort on your left side below your ribs
• Anemia, which occurs when you don’t have enough red blood cells

In people with CML, sections of two of their chromosomes switch places, creating a long chromosome 9 and a short chromosome 22, known as the Philadelphia chromosome. These changes lead to the creation of a new gene called BCR-ABL. This acquired gene mutation happens during your lifetime rather than being present at birth.

Normally, your bone marrow produces blood stem cells that mature into red blood cells, white blood cells, and platelets. But the new gene gives instructions to overproduce a protein that results in immature white blood cells, called blasts, to grow uncontrollably. As blasts build up in your bone marrow, your body has a harder time making healthy blood cells. 

CML is more likely to affect older adults, people assigned male at birth, and people who have been exposed to high levels of radiation.

CML has three phases, depending on how advanced it is. The number of blasts in your blood determines each phase and further refines the diagnosis.

• Chronic phase: Most people with CML are diagnosed in the chronic phase, when they have a small number of blasts in their blood or bone marrow. The chronic phase causes few or no symptoms and can often be controlled with medications. 
• Accelerated phase: In the accelerated phase, there are a larger number of blast cells in the bone marrow and blood. People in this phase may experience symptoms, including fevers, weight loss, and a change in appetite.
• Blast phase: The blast phase of CML is diagnosed when blast cells have spread to tissues and organs. People in this phase can have severe symptoms, like shortness of breath and fatigue. The blast phase of CML can accelerate into acute lymphocytic leukemia or acute myeloid leukemia.

At Penn Medicine, our providers have developed many treatments for blood cancer, including CAR T cell therapy, and we stay at the forefront of CML care. You’ll have access to these and other leading therapies, delivered by specialists in chronic myeloid leukemia. Our cancer nurse navigators support you through every step by helping you schedule appointments quickly and ensuring you understand your diagnosis and care plan.

Through our robust research program, we’re constantly working to develop new therapies for CML. You might qualify to participate in one of our nearly 100 active clinical trials in blood cancer. Wherever you are on your care journey, we’re here to guide you, with a focus on your long-term health and well-being.