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.

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