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Definition of Chronic myelogenous leukemia

Chronic myelogenous leukemia: A chronic malignant disease in which too many white blood cells belonging to the myeloid line of cells are made in the bone marrow. Early symptoms of this form of leukemia include fatigue and night sweats. The disease is due to the growth and evolution of an abnormal clone of cells containing a chromosome rearrangement known as the Philadelphia (or Ph) chromosome. Chronic myelogenous leukemia is commonly called CML. It is also known as chronic myelocytic leukemia and chronic granulocytic leukemia.

The bone marrow cells called blasts normally develop (mature) into several different types of blood cells that have specific jobs to do in the body. CML affects the blasts that are developing into white blood cells called granulocytes. These blasts do not mature normally and immature blast cells are found in the blood and bone marrow.

CML usually occurs in people who are middle-aged or older, although it also can occur in children. As a rule CML progresses slowly. In the first stages of CML, most people have no symptoms of cancer. When symptoms do appear, they may include a feeling of no energy, fever, lack of appetite, and night sweats. The spleen (in the right upper part of the abdomen) may be swollen and markedly enlarged.

If there are symptoms or when the disease is incidentally found, blood tests may be done to count the number of each of the different kinds of blood cells and to examine their appearance. If the results of the blood test are abnormal, a bone marrow biopsy may be done. During this test, a needle is inserted into a bone and a small amount of bone marrow is taken out and looked at under the microscope. Other tests that may be done include chromosome studies(karyotypes) of blood and bone marrow cells and molecular studies of these cells.

Staging of CML: Once CML has been diagnosed, more tests may be done to find out if the disease has been found early or later in its course. This is called staging. CML progresses through different phases and these phases are the stages used to plan treatment. The following stages are used for chronic myelogenous leukemia:

  • Chronic phase -- There are few blast cells in the blood and bone marrow and there may be no symptoms of leukemia. This phase may last from several months to several years.
  • Accelerated phase --There are more blast cells in the blood and bone marrow, and fewer normal cells.
  • Blastic phase -- More than 30% of the cells in the blood or bone marrow are blast cells and the blast cells may form tumors outside of the bone marrow in places such as the bone or lymph nodes. This is also called the blast crisis.
  • Refractory CML -- Leukemia cells do not decrease even though treatment is given.

Treatment: There are treatments for all patients with CML. These treatments may include:

  • chemotherapy (using drugs to kill cancer cells);
  • other cancer drug therapies such as imatinib (Gleevec), dasatinib (Sprycel), and nilotinib (Tasigna);
  • biologic therapy (a treatment that uses the patient's immune system to fight cancer)
  • radiation therapy (using high-dose x-rays or other high-energy rays to kill the leukemic cells);
  • high-dose chemotherapy with stem cell transplantation (to grow into and restore the body's blood cells);
  • donor lymphocyte infusion or DLI (after stem cell transplantation).
  • surgery (splenectomy, surgery to remove the spleen).

Chemotherapy uses drugs to kill cancer cells. Chemotherapy may be taken by pill, or it may be put into the body by a needle in the vein or muscle. Chemotherapy is called a systemic treatment because the drug enters the bloodstream, travels through the body, and can kill cancer cells throughout the body. Chemotherapy also can be put directly into the fluid around the brain and spinal cord through a tube inserted into the brain or back. This is called intrathecal chemotherapy.

Imatinib (Gleevec) is a new type of cancer drug, called a tyrosine kinase inhibitor. It blocks the enzyme, tyrosine kinase, that causes stem cells to develop into more white blood cells than the body needs. Gleevec is one of thekey gene-targeted drugs for the treatment of CML.

Radiation therapy uses x-rays or other high-energy rays to kill cancer cells and shrink tumors. Radiation for CML usually comes from a machine outside the body (external radiation therapy) is sometimes used to relieve symptoms or as part of therapy given before a bone marrow transplant.

Bone marrow transplantation is used to replace the patient's bone marrow with healthy bone marrow. First, all of the bone marrow in the body is destroyed with high doses of chemotherapy with or without radiation therapy. Healthy marrow is then taken from another person (a donor) whose tissue is the same as or almost the same as the patient's. The donor may be an identical twin (the best match), a brother or sister, or another person not related. The healthy marrow from the donor is given to the patient through a needle in the vein, and the marrow replaces the marrow that was destroyed. A bone marrow transplant using marrow from a relative or person not related to the patient is called an allogeneic bone marrow transplant.

Another type of bone marrow transplant, called autologous bone marrow transplant, is being tested in clinical trials. To do this type of transplant, bone marrow is taken from the patient and treated with drugs to kill any cancer cells. The marrow is then frozen to save it. The patient is given high-dose chemotherapy with or without radiation therapy to destroy all of the remaining marrow. The frozen marrow that was saved is then thawed and given back to the patient through a needle in a vein to replace the marrow that was destroyed.

High-dose chemotherapy with stem cell transplantation is a method of giving high doses of chemotherapy and replacing blood-forming cells destroyed by the cancer treatment. Stem cells (immature blood cells) are removed from the blood or bone marrow of the patient or a donor and are frozen and stored. After the chemotherapy is completed, the stored stem cells are thawed and given back to the patient through an infusion. These reinfused stem cells grow into (and restore) the body's blood cells.

Donor lymphocyte infusion (DLI) is a cancer treatment that may be used after stem cell transplantation. Lymphocytes (a type of white blood cell) from the stem cell transplant donor are removed from the donor's blood and may be frozen for storage. The donor's lymphocytes are thawed if they were frozen and then given to the patient through one or more infusions. The lymphocytes see the patient's cancer cells as not belonging to the body and attack them.

Biological therapy tries to get the body to fight cancer. It uses materials made by the body or made in a laboratory to boost, direct, or restore the body's natural defenses against disease. Biological therapy is sometimes called biological response modifier (BRM) therapy or immunotherapy.

If the spleen is greatly enlarged, the spleen may be removed in an operation called a splenectomy.

Treatment by stage: Standard treatment may be considered because of its effectiveness in patients in past studies, or participation in a clinical trial may be considered.

Chronic Phase CML: Treatment may be one of the following:

  • High-dose chemotherapy with donor stem cell transplantation.
  • Biological therapy (interferon) with or without chemotherapy.
  • Other drug therapy (Gleevec).
  • Chemotherapy to lower the number of white blood cells.
  • Surgery to remove the spleen (splenectomy).
  • A clinical trial of a new treatment.

Accelerated Phase CML: Treatment may be one of the following:

  • Stem cell transplantation.
  • Other drug therapy (Gleevec).
  • Biologic therapy (interferon) with or without chemotherapy.
  • High-dose chemotherapy.
  • Chemotherapy to lower the number of white blood cells.
  • High-dose chemotherapy.
  • Transfusion therapy to replace red blood cells, platelets, and sometimes white blood cells, to relieve symptoms and improve quality of life.
  • A clinical trial of a new treatment.

Blastic Phase CML: Treatment may be one of the following:

  • Other drug therapy (Gleevec).
  • Chemotherapy using one or more drugs.
  • High-dose chemotherapy.
  • Donor stem cell transplantation.
  • Chemotherapy as palliative therapy to relieve symptoms and improve quality of life.
  • A clinical trial of a new treatment.

Relapsed chronic myelogenous leukemia: Treatment may be one of the following:

  • Donor stem cell transplantation.
  • Donor lymphocyte infusion.
  • Biologic therapy (interferon).
  • A clinical trial of biologic therapy, combination chemotherapy, or other drug therapy (Gleevec).

The prognosis: The chance of recovery depends on a number of factors including the phase of CML, the amount of blasts in the blood or bone marrow, the size of the spleen at diagnosis, the patient's general health, and the patient's age.

Source: MedTerms™ Medical Dictionary
http://www.medterms.com/script/main/art.asp?articlekey=15477
Last Editorial Review: 9/20/2012

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