Chronic Myeloid Leukemia

Chronic myeloid leukemia (CML) is a cancer of the bone marrow and blood. It is a slow-growing leukemia that develops when a genetic change mutates or damages early (immature) myeloid cells, which are the cells that become white blood cells (other than lymphocytes), red blood cells or cells that make platelets.

The genetic change takes place when chromosomes from strands of DNA break off and swap places. This process is called a translocation. The resulting abnormal chromosome, the Philadelphia chromosome, is in the leukemia cells of almost all people with CML. The DNA swap causes the formation of the BCR-ABL gene, which produces the BCR-ABL protein. This protein helps CML cells grow and multiply at a much faster rate than normal white blood cells.

Diagnosing CML

CML cells grow slowly, and many people with CML may not have any symptoms when their cancer is diagnosed. The disease is often suspected because of the results of blood tests ordered for another problem or because of findings on a routine physical examination. In addition to a physical exam, several tests may be used to diagnose CML.

  • Complete blood count (CBC) measures the levels of white blood cells, red blood cells (including hematocrit and hemoglobin levels) and platelets in the blood. High blood cell counts may be an indication of CML.
  • Bone marrow aspiration and biopsy are often done at the same time. During these procedures, bone marrow tissue samples are removed for examination. A bone marrow biopsy involves removing a sample of marrow from within the bone. For bone marrow aspiration, a liquid portion of the bone marrow is removed.
  • Cytogenetic testing uses the study of the characteristics of chromosomes (genetic strands) under a microscope to find changes or alterations in the leukemia cells. This test may be used to identify the Philadelphia chromosome.
  • Fluorescence in situ hybridization (FISH) is a technique that uses fluorescent dyes to look for pieces of the BCR-ABL gene on chromosomes.
  • Polymerase chain reaction (PCR) can be used to look for the BCR-ABL gene.

Imaging tests, such as computed tomography (CT), magnetic resonance imaging (MRI), ultrasound and X-ray, may be done to help determine the extent of the disease.

Phases of CML

Doctors use the World Health Organization system to classify CML into three phases that help determine the prognosis (prediction of the outlook): chronic phase, accelerated phase and blast crisis phase (see Table 1). In most cases, CML is in the chronic phase at the time of diagnosis. The most advanced and aggressive phase is blast crisis phase.

Table 1. WHO Classification System

Phase Description
Chronic phase
▪ Immature (blast) cells make up less than 10% of the cells in bone marrow or blood.
Accelerated phase
This phase is determined by any of the following features:
▪ Blast cells make up 10% to 19% of cells in the bone marrow or blood OR
▪ Basophils make up at least 20% of the blood OR
▪ Very low platelet count not related to treatment OR
▪ Very high platelet count that does not decrease with treatment OR
▪ Increased size of the spleen OR
▪ Increased white blood cell count that does not decrease with treatment
Blast crisis phase
▪ Blast cells make up at least 20% of cells in the bone marrow or blood.
▪ Blast cells rapidly increase outside of the bone marrow.
▪ Large groups of blast cells found in bone marrow biopsy.
Used with permission of the American Joint Committee on Cancer (AJCC), Chicago, Illinois. The original and primary source for this
information is the AJCC Cancer Staging Manual, Eighth Edition (2017) published by Springer Science+Business Media.

Treating CML

After CML is diagnosed and a phase assigned, your health care team will work with you to determine the best treatment plan (see Forms of Leukemia).

  • Targeted therapy is the main treatment for CML. Targeted therapy drugs block the growth of leukemia cells by targeting specific parts of cancer cells. They are considered a systemic treatment because the drugs travel throughout the body in the bloodstream. The BCR-ABL tyrosine kinase protein that helps CML cells grow can be blocked by a type of targeted therapy drug called a tyrosine kinase inhibitor (TKI).
  • Chemotherapy drugs are used to stop the growth of cancer, either by killing cancer cells or by preventing them from growing and dividing. This form of treatment is also known as systemic therapy, meaning the drugs travel through the bloodstream and affect cells throughout the entire body. Chemotherapy drugs attack cancer cells that grow and multiply quickly, occasionally causing damage to healthy cells that also grow and multiply rapidly. Chemotherapy is usually given in cycles that consist of a treatment period followed by a break to allow healthy cells to recover.
  • Immunotherapy works with or stimulates a person’s own immune system to recognize and destroy cancer cells. Immunotherapy drugs can be used in combination with other treatments, as a maintenance therapy or alone.
  • Clinical trials may be a treatment option. Ask your doctor if a trial is right for you.

Stem Cell Transplantation

Stem cell transplantation (also known as bone marrow transplantation) is an infusion of healthy stem cells into the body. The healthy cells can be collected from blood or bone marrow from the patient, a family member or another donor. Umbilical cord blood that has been previously collected from a donated cord from a family (with no harm to baby or mother) and stored in a bank is also a potential option.

Allogeneic stem cell transplantation uses stem cells from a volunteer donor whose tissue type matches that of the patient and is the most common type of transplant used to treat leukemia. If available, a brother or sister could be a close tissue match because siblings share similar genes. If no family members are a tissue match to the patient, a matched unrelated donor (MUD) or matched donated umbilical cord blood may be found through a national registry.

People receiving allogeneic transplantation may experience graft-versus-host disease (GvHD) as a side effect of treatment. GvHD can occur when white blood cells from the donor (the graft) recognize cells in the body (the host) as foreign and attack them. This problem can cause damage to the skin, liver, intestines and other organs. GvHD can be treated with steroids or other drugs that suppress your immune system.

Additional Resources

Previous Next

Register Now! Sign Up For Our Free E-Newletter!

Read Inspiring Cancer Survivor Stories

Order Your Guides Here