Leukemia is the name of a number of malignant, or cancerous, diseases
of the blood-forming organs. The
acute and chronic leukemias, together
with the other types of tumors of the blood,
bone cells (myelomas), and
lymph tissue (lymphomas), cause about 10% of all cancer deaths and
about 50% of all cancer deaths in children and adults less than 30
years old.Leukemias are characterized by the appearance of
excessive amounts of
white blood cells, with death resulting from the
invasion of these cells into various tissues, particularly the bone
marrow, spleen, and lymph nodes. Diagnoses of these diseases are
generally made by two types of blood counts, "total" and
"differential." The general diagnosis is arrived at by noting a very
large increase in the total number of white blood cells. A more
specific diagnosis arises from comparing the relative numbers and types
of white cells. The type of
Leukemia derives its name from the major
Cell typeÑfor example, lymphoblastic and myeloblastic.As with
most cancers, the exact cause of most
leukemias has yet to be
established. Some animal leukemias are induced by viruses, such as Rous
chicken sarcoma, feline leukemia, and Rauscher mouse leukemia. Two
retroviruses have been identified as causes of human T-cell leukemia.
Chemicals such as benzene, chloramphenicol, and procarbazine, as well
as radiation, including that from low-frequency electromagnetic fields,
may be able to produce leukemia in humans. Genetic researchers have
been able to link certain chromosomal abnormalities with some forms of
leukemia.An individual with leukemia, more particularly the
chronic rather than acute forms, may not be aware of it unless, for
example, a blood count is done. As the condition progresses there may
be weakness, fatigue, loss of appetite, weight loss, anemia, enlarged
spleen, and bone pain. When untreated, acute leukemia is fatal in 1 to
2 years and often fatal within about 6 months of onset. Today''s therapy
produces 85 to 90% remissions for 3 or more years and apparent cure in
50% of the cases. Vigorous therapy is based on the premise that every
leukemic cell must be destroyed.In addition to radiation, the
following drugs, usually in combinations with one another, are used to
treat acute leukemias: vincristine, prednisone, methotrexate,
mercaptopurine, cyclophosphamide, cytarabine, and teniposide. In
chronic leukemia, busulfan, melphalan, and chlorambucil are used. These
drugs tend to make patients quite ill. Bone marrow transplants may be
used when other treatments have failed. A rare form of leukemia known
as hairy-cell leukemia has been found to respond to some degree to
interferon treatment, and research is currently being devoted to the
possibilities of treating myeloid leukemia with certain proteins that
occur naturally in the body.
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