Text A. Acute Lymphocytic Leukemia.

Acute lymphocytic (lymphoblastic) leukemia is a life-threatening disease in which the cells that normally develop into lymphocytes become cancer­ous and rapidly replace normal cells in the bone marrow.

Acute lymphocytic leukemia, the most com­mon cancer in children, accounts for 25 percent of all cancers in children under age 15. It most often affects children between the ages of 3 and 5 but can also affect adolescents and, less com­monly, adults.

Very immature cells that normally develop into lymphocytes become cancerous. These leukemic cells accumulate in the bone marrow, destroying and replacing cells that produce normal blood cells. They're released into the bloodstream and transported to the liver, spleen, lymph nodes, brain, kidneys, and reproductive organs, where they continue to grow and divide. They can irri­tate the lining of the brain, causing meningitis, and can cause anemia, liver and kidney failure, and other organ damage.

Symptoms

The first symptoms usually occur because the bone marrow fails to produce enough normal blood cells. These symptoms include weakness and shortness of breath, resulting from too few red blood cells (anemia); infection and fever, resulting from too few normal white blood cells; and bleeding, resulting from too few platelets. In some people, a severe infection is the first problem, but in others, the onset is more subtle, with progres­sive weakness, fatigue, and paleness. Bleeding may occur in the form of nosebleeds, gums that bleed easily, purple skin blotches, or easy bruising. Leukemic cells in the brain may cause head­aches, vomiting, and irritability, and those in the bone marrow may cause bone and joint pain.

Diagnosis

Common blood tests, such as the complete blood cell count, can provide the first evidence that a person has leukemia. The total number of white blood cells may be decreased, normal, or increased, but the number of red blood cells and platelets is almost always decreased. More im­portant, very immature white blood cells (blasts) are seen in blood samples examined under a mi­croscope. Since blasts aren't normally seen in the blood, their presence may be all that is needed to diagnose leukemia. However, a bone marrow biopsy is almost always performed to confirm the diagnosis and determine the type of leukemia.

Prognosis and Treatment

Before treatment was available, most people who had acute leukemia died within 4 months of diagnosis.. Now, many people are cured. For more than 90 percent of people who have acute lymphocytic leukemia (usually children), the first course of chemotherapy brings the disease under control (remission). The disease returns in many, but 50 percent of children show no signs of the leukemia 5 years after treatment. Children be­tween the ages of 3 and 7 have the best prognosis; people over age 20 fare less well. Children or adults whose initial white blood cell counts are lower than 25,000 cells per microliter of blood tend to have a better prognosis than those whose white blood cell counts are initially higher.

The goal of treatment is to achieve complete remission by destroying leukemic cells so that normal cells can once again grow in the bone mar­row. A person receiving chemotherapy may need to stay in the hospital for a few days or weeks, depending on how quickly the bone marrow re­covers. Before normal bone marrow function re­turns, the person may need to have red blood cell transfusions to treat anemia, platelet transfusions to treat bleeding, and antibiotics to treat infec­tions.

Several combinations of chemotherapy drugs are commonly used, and doses are repeated for several days or weeks. One combination consists of prednisone taken by mouth and weekly doses of vincristine with either anthracycline or asparaginase given intravenously. Other drugs are being investigated.

For treatment of leukemic cells in the brain, methotrexate is usually injected directly into the spinal fluid, and radiation therapy is applied to the brain. Even when a doctor has little evidence that the cancer has spread to the brain, some type of treatment is usually applied there. A few weeks or months after the initial, intensive treatment aimed at destroying leukemic cells, additional treatment (consolidation chemotherapy) is given to destroy any remaining leukemic cells. Treatment may last 2 to 3 years, although some courses are somewhat shorter.

Leukemic cells may begin to appear again (re­lapse), often in the bone marrow, brain, or testes. The reappearance of leukemic cells in the bone marrow is particularly serious. Chemotherapy must be given again, and although most people respond to treatment, the disease has a strong tendency to come back. Bone marrow transplan­tation offers these people the best chance of cure, but this procedure can be performed only if bone marrow can be obtained from a person who has a compatible tissue type (HLA-matched)—almost always a close relative. When leukemic cells reappear in the brain, chemotherapy drugs are injected into the spinal fluid one or two times a week. Treatment of relapse involving the testes consists of chemotherapy along with radiation therapy.

 

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