Chronic myelocytic (myeloid, myelogenous, granulocytic) leukemia is a disease in which cells that normally would develop into neutrophils, basophils, eosinophils, and monocytes become cancerous. * People pass through a phase in which they have nonspecific symptoms such as tiredness, anorexia, and weight loss. * As the disease progresses, the lymph nodes and spleen enlarge, and people may also be pale and bruise or bleed easily. * Blood tests, bone marrow examination, and chromosome analysis are needed for diagnosis. * Treatment is with imatinib Some Trade Names GLEEVEC or with high doses of chemotherapy drugs followed by stem cell transplantation. Chronic myelocytic leukemia (CML) may affect people of any age and of either sex but is uncommon in children younger than 10 years. The disease most commonly develops in adults between the ages of 40 and 60. The cause usually is a rearrangement of two particular chromosomes into what is called the Philadelphia chromosome. The Philadelphia chromosome produces an abnormal enzyme (tyrosine kinase), which is responsible for the abnormal growth pattern of the white blood cells in CML. In CML, most of the leukemia cells are produced in the bone marrow, but some are produced in the spleen and liver. In contrast to the acute leukemias, in which large numbers of immature white blood cells (blasts) are present, the chronic stage of CML is characterized by marked increases in the numbers of normal-appearing white blood cells and sometimes platelets. During the course of the disease, more and more leukemia cells fill the bone marrow and others enter the bloodstream. Eventually the leukemia cells undergo more changes, and the disease progresses to an accelerated phase and then inevitably to blast crisis. In blast crisis, only immature leukemia cells are produced, a sign that the disease has become much worse. Massive enlargement of the spleen is common in blast crisis, as well as fever and weight loss.
Early on, in its chronic stage, CML may produce no symptoms. However, some people become fatigued and weak, lose their appetite, lose weight, develop a fever or night sweats, and notice a sensation of being full—which is usually caused by an enlarged spleen. As the disease progresses to blast crisis, people become sicker because the number of red blood cells and platelets decreases, leading to paleness, bruising, and bleeding
The diagnosis of CML is suspected based on the results of a simple blood test. The test may show an abnormally high white blood cell count. In blood samples examined under a microscope, less mature white blood cells, normally found only in bone marrow, are seen. Tests that analyze chromosomes (cytogenetics or molecular genetics) are needed to confirm the diagnosis by detecting the Philadelphia chromosome.
Although most treatments do not cure the disease, they do slow its progress. The drug imatinib Some Trade Names GLEEVEC and similar newer drugs block the abnormal enzyme produced by the Philadelphia chromosome. These drugs are more effective than other treatments and cause only minor side effects. With imatinib Some Trade Names GLEEVEC therapy, taken by mouth, survival is over 90% at 5 years past diagnosis
Stem cell transplantation (see Transplantation: Stem Cell Transplantation) combined with high doses of chemotherapy drugs may cure CML. However, only certain people can have transplantation. Stem cells must come from a donor who has a compatible tissue type, usually a sibling. Transplantation is most effective during the early stage of the disease and is considerably less effective if the CML is rapidly progressing or there is a blast crisis. People in a blast crisis live only a few months without treatment. Treatment with imatinib Some Trade Names GLEEVEC plus chemotherapy drugs sometimes extends survival to 12 months or more. There are also older chemotherapy regimens that can be given to people who relapse after receiving imatinib Some Trade Names GLEEVEC or who have CML without a Philadelphia chromosome. The main drugs used are busulfan Some Trade Names MYLERAN , hydroxyurea Some Trade Names HYDREA , and interferon. None of these drugs prolongs survival but, they may help relieve symptoms.