Major Forms of Cancer - Leukemia



Because leukemia involves blood cells circulating through the body rather than a fixed mass of tissue, leukemia is sometimes not considered a true cancer. However, leukemia cells, when studied under the microscope and in cell cultures, behave like cancer cells found in tumors.

There are at least ten different kinds of blood cells that have been identified with various forms of the disease. In addition, there are both acute and chronic forms of leukemia, such as acute granulocytic leukemia and chronic lymphocytic leukemia , named after the particular kind of white blood cells that are most affected.

Leukemia affects the blood-forming tissues, such as the bone marrow, resulting in an overproduction of white blood cells. The disease is particularly lethal to children under the age of 15; more than 10 percent of the leukemia deaths each year are among children. The incidence by age group varies according to the specific type of leukemia, however; one variety of acute granulocytic leukemia can occur at any age, but chronic lymphocytic leukemia usually does not appear before the age of 40. Men are more likely than women to be the victims of one of the various forms of leukemia.

Symptoms

Common symptoms to all leukemias include fever, weight loss, fatigue, bone pain, anemia as expressed in paleness, and an enlarged spleen or masses under the skin caused by an accumulation of leukemic cells. There may be skin lesions and a tendency to bleed. Infections may become more common and less responsive to treatment because of a loss of the normal blood cells needed to resist disease.

Detection

Diagnosis of leukemia from early symptoms may be difficult because they resemble those of mononucleosis and other infections. Biopsies of bone marrow and careful blood studies usually identify the disease.

Therapy

Treatment usually is directed toward reducing the size of the spleen and the number of white cells in the blood, and increasing the level of blood hemoglobin to counteract the effects of anemia. Antibiotics may be included to help control infections when natural resistance to disease has been lowered. X-ray treatments, radioactive phosphorus, anticancer drugs, and steroid hormone medications are administered according to the needs of the individual patient and the type of leukemia being treated.

Acute leukemia may be fatal within a few weeks of the onset of symptoms. But chronic cases receiving proper treatment have been known to survive more than 25 years. Remission rates are improving, partly because of new drugs and methods of treatment. The new chemotherapeutic approaches include the following:

  1. • For acute leukemia in children, methotrexate has been used with increasing success. One of the anti-metabolites, the family of drugs that interfere with development of essential cell components, methotrexate reduces the production in the blood of folic acid. In that way the drug competes with the cancer cells for the vital enzyme folic reductase—and inhibits the cancer's growth.
  2. • In adults, chronic and acute forms of leukemia may be treated with chlorambucil or cyclophosphamide . Both drugs are types of nitrogen mustard. Both may produce such side effects as suppression of bone marrow, loss of hair, nausea, dizziness, and vomiting.
  3. • In cases of acute leukemia in childhood, the vinca alkaloid drags have proved valuable. These drugs, such as vincristine sulfate , are extremely powerful. They attack active cancer cells more directly than they attack normal cells. They may lead to such side effects as headaches, convulsions, and loss of some muscular control.

Other drugs in the alkaloid and other drug families have been used to treat leukemia. The others include cytosine arabinoside , which works to prevent cell synthesis—including cancer-cell synthesis; 6-Mercaptopurine, which inhibits some metabolic processes; and busulfan and similar drugs, which work against multiplication of the cancer cells. Antitumor antibiotics that prevent growth of cancer cells include daunorabicin, doxorubicin, and bleomycin.

Causes

There is no general theory about the cause of leukemia. Animals are known to be susceptible to a form of leukemia transmitted by virus, but there is no solid evidence that human leukemias are caused by viral infections. Survivors of nuclear explosions as well as persons exposed to large doses of X rays have developed leukemia at a higher-than-normal rate than other people. There is evidence that at least one type of acute leukemia may be a result of an inherited genetic defect.



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