Leukemia

Leukemia

A set of related cancers that form in the bone marrow and other blood-producing organs.

Leukemia is named after the leukocytes, white blood cells which mutate before maturity and become cancerous. These cells reproduce rapidly, suppressing production of normal white cells that are essential to fighting infection in the body, and red cells that are needed to carry oxygen in the blood. Cancer cells may spread to the liver, spleen, lymph nodes, genitals, or the brain.

After accidents, leukemia is the leading cause of death for children ages 2-15. It is the most common form of cancer among children, accounting for up to one-third of childhood cancers. Of 28,000 cases diagnosed per year, 2,500 are children. The incidence of leukemia peaks between the ages of 3-5 for whites, but remains constant up until age 20 for non-white populations. There are several types of leukemia, depending on the type of blood cell affected and the course of development. It may be chronic, slowly progressing with few symptoms for up to 20 years or more, or acute, with sudden onset and rapid progression of symptoms requiring immediate hospitalization and treatment. Most childhood leukemia is acute: 75% of cases are of the acute lymphocytic type, 20% are acute myelocytic, and 5% are chronic myelocytic ("cytic"= of the cell). Chromosomal abnormalities predispose children to develop leukemia, and Down syndrome children in particular are 30 times more likely than others to be leukemia Long-term exposure or direct contact with chemicals found in some herbicides and pesticides has been shown to induce leukemia, and many identified chemicals were banned during the 1970s. Studies have also attributed some leukemia to long-term exposure to high-voltage power lines (due to their magnetic fields). A 1996 report by the National Research Council found no conclusive evidence linking power lines to cancers, but did acknowledge an unexplained link between leukemia and the high magnetic fields that the lines produce (See Electric and magnetic fields).

Early symptoms of leukemia are high fever, recurrent infections, bleeding of the gums or nose, bruising, bone pain or tenderness, fatigue, headaches, and swelling in the neck, armpit, or groin. Diagnosis will be based on a blood sample and confirmed by a bone marrow biopsy, where a syringe is inserted into the spine. Until the 1960s leukemia was almost always fatal—within a matter of months for the acute forms. Yet, since the development and specialization of chemo-(drug), radiation(x ray), and transfusion therapies, a large proportion of childhood leukemia is now curable. Estimates range from 50-70% survival rates for the most common form, acute lymphocytic leukemia (ALL). Children diagnosed between the ages of 3-9 have the best prognosis.

The primary issue in treating leukemia is to kill the cancerous blood cells while preserving the healthy ones. Treatment involves three basic stages: induction, consolidation, and maintenance. The patient may take antibiotics throughout the process in order to fight infection. During the induction phase the goal is to induce remisssion, i.e., to stop cancer cells from multiplying and to drastically lower the percentage of eixsting ones through "rapid cell kill." The patient is exposed to extremely high doses of chemotherapy, either orally or by injection, or radiation therapy, where χ rays are directed at tumorous areas. Because the drugs kill healthy white cells as well as cancerous ones, the patient will become extremely vulnerable to bacterial and fungal infections as the immune system is weakened.

The primary side effects of the medication itself are hair loss and nausea, which can sometimes be severe. After remission is achieved, during the consolidation phase the goal is essentially to reactivate the patient's immune system. This may be done with further chemotherapy (sometimes using different drugs) or by a bone-marrow transplant, which introduces new, healthy white cells. Generally bone marrow transplants are not attempted until a relapse has occured and chemotherapy has been found ineffective. If a transplant is necessary, marrow from a compatible donor—ideally a sibling, or from the patient's own body will be used. Unfortunately, about 5-10% of transplant recipients die from the transplant itself, due to the body's rejection of foreign cells (known as graft vs. host rejection) and other complications. A newer form of transplant, where the patient's own marrow is removed, "cleaned" of cancerous cells and then reinjected into the body avoids the graft-host problem, but its efficacy is disputed.

The final phase of leukemia treatment, maintenance, lasts from one to three years, during which the patient stays under surveillance and may receive periodic chemotherapy, transfusions, and radiation. During this phase the child's hair will usually grow back, other side effects subside, and he or she can return to school. If a relapse occurs, the consolidation phase may begin again and some form of transplant used, but after a certain point the level of toxicity entailed in treating the leukemia would be equal to or greater than the damage done by the cancer itself. Treatment is usually stopped after two years, and if relapse occurs, the disease is allowed to take its course.

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Author Info: , Thomson Gale, Detroit, Gale Encyclopedia of Childhood and Adolescence, 1998

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