Home > Encyclopedia of Nursing & Allied Health > Leukemias, Acute

Definition

Acute leukemia is a type of cancer in which excessive quantities of abnormal white blood cells are produced.

Description

Medical science further classifies acute leukemia by the type of white blood cell that undergoes mutation. The most common of these are:

• Acute lymphoblastic leukemia (ALL), in which excessive quantities of lymphoblasts, or immature lymphocyte white blood cells, are produced.
• Acute myeloblastic leukemia (AML), also known as acute nonlymphocytic leukemia (ANLL), in which excessive quantities of other types of immature white blood cells are produced.

Acute leukemias progress rapidly, while the chronic leukemias progress more slowly. The vast majority of the childhood leukemias are of the acute form.

The cells that make up blood are produced in the bone marrow and the lymphatic system. Bone marrow is the spongy tissue found in the large bones of the body. The lymphatic system includes the spleen (an organ in the upper abdomen), the thymus (a small gland beneath the breastbone), and the tonsils (a mass of lymphatic tissue located in the throat). In addition, the lymphatic vessels (tiny tubes that branch like blood vessels into all parts of the body) and lymph nodes (pea-shaped organs that are found along the network of lymphatic vessels) are also part of the lymphatic system. Lymph is a milky fluid that contains cells. Clusters of lymph nodes are found in the neck, underarm, pelvis, abdomen, and chest.

The cells found in the blood include red blood cells (RBCs) that carry oxygen and other materials to all tissues of the body; white blood cells (WBCs) that fight infection; and platelets, which play an important role in the clotting of the blood. White blood cells can be further subdivided into three main types: granulocytes, monocytes, and lymphocytes.

The granulocytes, as their name suggests, have particles (granules) inside them. These granules contain special proteins (enzymes) and several other substances that can break down chemicals and destroy microorganisms, such as bacteria. Monocytes are the second type of white blood cell. They are also important in defending the body against pathogens.

Lymphocytes are the third type of white blood cell. There are two primary types of lymphocytes—T lymphocytes and B lymphocytes—with different functions in the immune system. B cells protect the body by making antibodies. Antibodies are proteins that can attach to the surfaces of bacteria and viruses. This "attachment" sends signals to many other cell types to come and destroy the antibody-coated organism. T cells protect the body against viruses. When a virus enters a cell, it produces certain proteins that are projected onto the surface of the infected cell. T cells recognize these proteins and make certain chemicals that are capable of destroying the virus-infected cells. In addition, T cells can destroy some types of cancer cells.

Bone marrow makes stem cells, which are the precursors of the different blood cells. These stem cells mature through stages into either RBCs, WBCs, or platelets. In acute leukemias, the maturation process of the white blood cells is interrupted. The immature cells (or "blasts") proliferate rapidly and begin to accumulate in various organs and tissues, thereby affecting their normal function. This uncontrolled proliferation of the immature cells in the bone marrow affects the production of the normal red blood cells and platelets as well.

As noted, there are two types of acute leukemias—acute lymphocytic leukemia and acute myelogenous leukemia. Different types of white blood cells are involved in the two leukemias. In acute lymphocytic leukemia (ALL), it is the T or the B lymphocytes that are involved. The B cell leukemias are more common than T cell leukemias. Acute myelogenous leukemia, also known as acute nonlymphocytic leukemia (ANLL), is a cancer of the monocytes and/or granulocytes.

Leukemias account for 2% of all cancers. Because leukemia is the most common form of childhood cancer, it is often regarded as a disease of childhood. However, leukemias affect far more adults than children. Half of the cases occur in people who are 60 years of age or older. The incidence of acute and chronic leukemias is about the same. According to the estimates of the American Cancer Society (ACS), approximately 29,000 new cases of leukemia are diagnosed each year in the United States. Of these, 27,000 will be diagnosed in adults, 2,000 in children.

Causes and symptoms

Leukemia strikes both sexes and all ages. The human T-cell leukemia virus (HTLV-I), a virus with similarities to the human immunodeficiency virus (HIV), is believed to be the causative agent for some kinds of leukemias, but this has not yet been proven, and the cause of most leukemias is not known. Acute lymphoid leukemia (ALL) is more common among Caucasians than among African-Americans, while acute myeloid leukemia (AML) affects both races equally. The incidence of acute leukemia is slightly higher among men than women. People with Jewish ancestry have a higher likelihood of getting leukemia. A higher incidence of leukemia has also been observed among persons with Down syndrome and some other genetic abnormalities.

Reports in Science News cited studies that found a gene that regulates folic acid metabolism in the body to be more prevalent in acute lymphocytic leukemia (ALL) patients. Folic acid is known to be involved in the process of DNA maintenance and repair, and this gene diverts folic acid from this function. It is therefore hypothesized that this gene plays a role in the development of ALL, and that folic acid supplementation could lower the risk for developing ALL. This gene has not been found to play a part in other leukemias, such as AML.

Exposure to ionizing radiation, such as occurred in Japan after the atomic bomb explosions, has been shown to increase the risk of getting leukemia. Electromagnetic fields are suspected of being a possible cause, as are certain organic chemicals, such as benzene. Having a history of diseases that damage the bone marrow, such as aplastic anemia, or a history of cancers of the lymphatic system puts people at a high risk for developing acute leukemias. Similarly, the use of anticancer medications, immunosuppressants, and the antibiotic chloramphenicol are also considered risk factors for developing acute leukemias.

The symptoms of leukemia are generally vague and non-specific. A patient may experience all or some of the following symptoms:

• weakness or chronic fatigue
• fever of unknown origin, chills and flu-like symptoms
• weight loss that is not due to dieting or exercise
• frequent bacterial or viral infections
• headaches
• skin rash
• non-specific bone pain
• easy bruising
• bleeding from gums or nose
• blood in urine or stools
• swollen and tender lymph nodes and/or spleen
• abdominal fullness
• night sweats
• petechiae, or tiny red spots under the skin
• more rarely, sores in the eyes or on the skin

Diagnosis

For a successful outcome, treatment for acute leukemia must begin as soon as possible, but there are no screening tests available. If the doctor has reason to suspect leukemia, he or she will conduct a very thorough physical examination to look for enlarged lymph nodes in the neck, underarm, and pelvic region. Swollen gums, enlarged liver or spleen, bruises, or pinpoint red rashes all over the body are some of the signs of leukemia. Urine and blood tests may be ordered to check for microscopic amounts of blood in the urine and to obtain a complete differential blood count. This count will give the numbers and percentages of the different cells found in the blood. An abnormal blood test might suggest leukemia; however, the diagnosis must be confirmed by more specific tests.

The doctor may perform a bone marrow biopsy to confirm the diagnosis of leukemia. During the biopsy, a cylindrical piece of bone and marrow is removed. The tissue is generally taken out of the hipbone. These samples are sent to the laboratory where they are examined under a microscope by a hematologist, oncologist, or pathologist. In addition to the diagnostic biopsy, another biopsy will also be performed during the treatment phase of the disease to see if the leukemia is responding to therapy.

A spinal tap (lumbar puncture) is another procedure that the doctor may order to diagnose leukemia. In this procedure, a small needle is inserted into the spinal cavity in the lower back to withdraw some cerebrospinal fluid and to look for leukemic cells.

Standard imaging tests, such as x rays, computed tomography scans (CT scans), and magnetic resonance imaging (MRI) may be used to check whether the leukemic cells have invaded other areas of the body, such as the bones, chest, kidneys, abdomen, or brain. A gallium scan or bone scan is a test in which a radioactive chemical is injected into the body. This chemical accumulates in the areas of cancer or infection, allowing them to be viewed with a special camera.

Treatment

As noted, treatment must be begun as soon as possible. The goal of treatment is remission, or an arresting of the disease process of the leukemia. There are two phases of treatment for leukemia. The first phase is called induction therapy. As the name suggests, during this phase, the primary aim of the treatment is to reduce the number of leukemic cells as much as possible and induce a remission in the patient. Once the patient shows no obvious signs of leukemia (no leukemic cells are detected in blood tests and bone marrow biopsies), the patient is said to be in remission.

The second phase of treatment is then initiated. This is called continuation or maintenance therapy, and the goal is to kill any remaining cancer cells and to maintain the remission for as long as possible.

Chemotherapy

Chemotherapy is the use of drugs to kill cancer cells. It is usually the treatment of choice in leukemia, and is used to relieve symptoms and achieve long-term remission of the disease. Generally, combination chemotherapy, in which multiple drugs are used, is more efficient than using a single drug for the treatment. Some drugs may be administered intravenously through a vein in the arm; others may be given by mouth in the form of pills. If the cancer cells have invaded the brain, then chemotherapeutic drugs may be put into the fluid that surrounds the brain through a needle in the brain or back.

This is known as intrathecal chemotherapy. Because leukemia cells can spread to all the organs via the blood stream and the lymphatic vessels, surgery is not considered an option for treating leukemias.

Radiation

Radiation therapy, which involves the use of x rays or other high-energy rays to kill cancer cells and shrink tumors, may be used in some cases. For acute leukemias, the source of radiation is usually outside the body (external radiation therapy). If the leukemic cells have spread to the brain, radiation therapy can be given to the brain.

Bone marrow transplantation

Bone marrow transplantation is a process in which the patient's diseased bone marrow is replaced with healthy marrow. There are two ways of doing a bone marrow transplant. In an allogeneic bone marrow transplant, healthy marrow is taken from a donor whose tissue is either the same as or very closely resembles the patient's tissues. The donor may be a twin, a brother or sister (sibling), or a person who is not related at all. First, the patient's bone marrow is destroyed with very high doses of chemotherapy and radiation therapy. Healthy marrow from the donor is then given to the patient through a needle in a vein to replace the destroyed marrow.

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KEY TERMS

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Antibodies—Proteins made by the B lymphocytes in response to the presence in the body of infectious agents, such as bacteria or viruses.

Biopsy—The surgical removal and microscopic examination of living tissue for diagnostic purposes.

Chemotherapy—Treatment with drugs that act against cancer.

Computerized tomography (CT) scan—A series of x rays put together by a computer in order to form detailed pictures of areas inside the body.

Cytokines—Chemicals made by the cells that act on other cells to stimulate or inhibit their function. Cytokines that stimulate growth are called growth factors.

Immunotherapy—Treatment of cancer by stimulating the body's immune defense system.

Lumbar puncture—A procedure in which the doctor inserts a small needle into the spinal cavity in the lower back to withdraw some spinal fluid for testing. Also known as a spinal tap.

Magnetic resonance imaging (MRI)—A medical procedure using a magnet linked to a computer to picture areas inside the body.

Maturation—The process by which stem cells transform from immature cells without a specific function into a particular type of blood cell with defined functions.

Radiation therapy—Treatment using high-energy radiation from x-ray machines, cobalt, radium, or other sources.

Remission—A disappearance of a disease as a result of treatment. Complete remission means that all disease is gone. Partial remission means that the disease is significantly improved by treatment, but residual traces of the disease are still present.

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In the second type of bone marrow transplant, called an autologous bone marrow transplant, some of the patient's own marrow is taken out and treated with a combination of anticancer drugs to kill all the abnormal cells. This marrow is then frozen to preserve it. The marrow remaining in the patient's body is destroyed with high-dose chemotherapy and radiation therapy. The marrow that was frozen is then thawed and given back to the patient through a needle in a vein. This type of bone marrow transplant is currently being investigated in clinical trials.

Biological therapy or immunotherapy is a mode of treatment in which the body's own immune system is harnessed to fight the cancer. Interferon is a biological therapy that is increasingly being used. Substances that are routinely made by the immune system (such as growth factors, hormones, and disease-fighting proteins) are either synthetically made in a laboratory or their effectiveness is boosted and they are then put back into the patient's body. This treatment mode is also being investigated in clinical trials all over the country at major cancer centers.

Prognosis

Like all cancers, the prognosis for leukemia depends on the patient's age and general health. According to statistics, more than 60% of the patients with leukemia survive for at least a year after diagnosis. Acute myelocytic leukemia (AML) has a poorer prognosis rate than acute lymphocytic leukemias (ALL) and the chronic leukemias. In the last 15 to 20 years, the five-year survival rate for patients with ALL has increased from 38% to 57%.

Interestingly enough, since most childhood leukemias are of the ALL type, chemotherapy has been highly successful in their treatment. This is because chemotherapeutic drugs are most effective against actively growing cells. Due to the new combinations of anti-cancer drugs being used, the survival rates among children with ALL have improved dramatically. Ninety-five percent of all childhood ALL patients will enter remission, and 60–75% will remain in remission after five years, depending upon the type. T-cell ALL is considered cureable in half of all cases, while B-cell ALL is rarely, if ever cureable. The worst prognosis is for non-typable ALL, whose victims are usually below one year of age.

Health care team roles

In most cases, a diagnosis of leukemia is made in a physician's office, a general medical clinic, or emergency room by a primary care practitioner. Children and adolescents with leukemia are likely to be diagnosed by their primary care physician, or pediatrician. However, oncologists, or physicians that specialize in the diagnosis and treatment of cancer are also often involved. Hematologists, physicians that specialize in the diagnosis and treatment of disorders of the blood and the organs that produce blood cells, may become involved through consultation. A pathologist, or physician who specializes in studying tissue and cell samples, often to assist other physicians in reaching the correct diagnosis, also may be consulted.

Both registered nurses and licensed practical nurses provide direct care to leukemia patients in general hospitals, homes, or other healthcare facilities. Good supportive nursing care and observation are necessary to:

• Prevent or monitor for the infections to which leukemia patients are so susceptible.
• Monitor for anemia and bleeding.
• Assist in treatments such as chemotherapy, radiation, bone-marrow transplantation, or in giving blood transfusions.
• Monitor vital signs.
• Provide teaching regarding the prevention of infection, the normal course of leukemia, including the fatigue so many patients feel, the signs and symptoms of anemia, and good dental care (both leukemia and chemotherapy are apt to cause sensitivity in the mouth, vulnerability to infection and bleeding).

Clinical laboratory scientists draw blood samples that are ordered by the physician to monitor the leukemia from the outset, during treatment, and also during remission. Radiologic technologists take x rays to visualize and monitor parts of the body that may be affected by the leukemia.

Prevention

Most cancers can be prevented by changes in lifestyle or diet, which will reduce the risk factors. However, in leukemias, there are no such known risk factors. Therefore, at the present time, no way is known to prevent leukemias from developing. People who are at an increased risk for developing leukemia because of proven exposure to ionizing radiation or exposure to the toxic liquid benzene, and people with Down syndrome, should undergo periodic medical checkups.

Joan M. Schonbeck