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

Definition

Chronic leukemia is a type of cancer in which excessive quantities of abnormal white blood cells are produced, usually slowly, often over a period of years.

Description

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

• Chronic lymphocytic leukemia (CLL), in which mature-appearing white blood cells called lymphocytes are produced.
• Chronic myeloid (or myelogenous) leukemia (CML), also known as chronic granulocytic leukemia (CGL), is the result of uncontrolled proliferation of white blood cells called granulocytes.

Chronic leukemias are much less rapid-growing than acute leukemia, and affect adults far more often than children. In fact, nearly all the people who develop CLL are over 50 years of age. CML is also a disease primarily of middle-aged to elderly people, but 3% of all childhood leukemias are classified as CML, and the average age for developing CML is between ages 10 and 12.

The cells that make up blood are produced in the bone marrow and the lymph system. The bone marrow is the spongy tissue found in the large bones of the body. The lymph system includes the spleen (an organ in the upper abdomen), the thymus (a small organ beneath the breastbone), and the tonsils (an organ in the throat). The lymph vessels (tiny tubes that branch like blood vessels into all parts of the body) and lymph nodes (small peashaped organs that are found along the network of lymph vessels) are also part of the lymph system. The lymph itself 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 are the red blood cells (RBCs), which carry oxygen and other materials to all tissues of the body; white blood cells (WBCs), which fight infection; and the platelets, which play an important role in the clotting of the blood. The white blood cells can be further subdivided into three main types: granulocytes, monocytes, and lymphocytes.

The granulocytes have particles (granules) inside them that 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.

The lymphocytes form the third type of white blood cell. The two primary types of lymphocytes, T lymphocytes and B lymphocytes, have different functions within the immune system. The B cells protect the body by making antibodies, which are proteins that can attach to the surfaces of bacteria and viruses. This attachment sends signals to many other cell types to destroy the anti-body-coated organism. The 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. The T cells recognize these proteins and make certain chemicals that are capable of destroying the virus-infected cells. In addition, the T cells can destroy some types of cancer cells.

The bone marrow makes stem cells, which are the precursors of the different blood cells. Stem cells mature into RBCs, WBCs, or platelets. In chronic leukemias, blood cells suddenly begin to 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.

Different types of white blood cells are involved in chronic lymphocytic leukemia and chronic myeloid leukemia. Although some blasts, or immature cells (the hallmark of acute leukemia), are also present in chronic leukemia, it is the T or B lymphocytes that gradually mutate and become cancerous. The scenario is similar for chronic myelogenous leukemia, also known as chronic granulocytic leukemia (CGL), which occurs when unusually large numbers of granulocytes begin to appear in the bloodstream.

Leukemias account for 2% of all cancers. 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, 2000 in children. Leukemia is the most common form of childhood cancer, and it is often regarded as a disease of childhood However, leukemias, especially chronic leukemia, affect far more adults than children. Half of all leukemia cases occur in people who are 60 years of age or older, and the over-whelming majority of chronic leukemias occur in adults. The incidence of both acute and chronic leukemias is about the same.

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 immunovirus (HIV), is believed to be the causative agent for some kinds of leukemias, but this has not yet been proven. To date, the cause of most leukemias is not known. Lymphoid leukemias are more common among Caucasians than among African-Americans, while myeloid leukemias affects both races equally. The incidence of leukemia is slightly higher among men than women. People with Jewish ancestry have a higher like-lihood of getting leukemia. A higher incidence of leukemia has also been observed among persons with Down syndrome and some other genetic abnormalities. Patients with chronic myeloid leukemia often show a chromosome abnormality called the Philadelphia chromosome, that occurs when one chromosome attaches to another.

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 leukemias. Similarly, the use of anticancer medications, immunosuppressants, and the antibiotic chloramphenicol are also considered risk factors for developing leukemias.

The symptoms of chronic leukemia are generally vague and non-specific, and are frequently overlooked until they are noticed on routine physical examination, especially when a routine blood test such as a complete blood count (CBC) is performed. A CBC may show unusually large numbers of a certain type of lymphocyte in the blood. Chronic leukemias may go for years without manifesting any symptoms at all, but also can develop symptoms similar to acute leukemias. Chronic myeloid leukemia, in particular, has two phases, a chronic one that can last for several years, and a malignant phase in which immature granulocytes are suddenly generated in huge numbers, producing similar symptoms to acute leukemia. In such cases, a patient may experience all or some of the following symptoms:

• weakness or chronic fatigue
• fever of unknown origin, chills, and flu-like symptoms
• unexplained weight loss
• frequent bacterial or viral infections
• viscous (sticky) blood (which slows down the supply to various organs)
• headache
• 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
• priapism, or persistent, painful erection of the penis
• rarely, sores in the eyes or on the skin

Diagnosis

As noted, there are often no symptoms present for chronic leukemia, and there are no screening tests available. If the physician has reason to suspect leukemia, a very thorough physical examination will be conducted 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, which gives the numbers and percentages of the different cells found in the blood. An abnormal blood test might suggest leukemia. However, the diagnosis has to be confirmed by more specific tests.

The physician may perform a bone marrow biopsy, during which a cylindrical piece of bone and marrow is removed, generally taken from hipbone. A spinal tap (lumbar puncture) is another procedure that may be ordered. 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 (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. The chemical accumulates in the areas of cancer or infection, allowing them to be viewed with a special camera.

Treatment

The need for treatment is assessed according to the degree of enlargement of the liver and spleen, a serious decline in the number of platelets in the blood, and whether or not anemia is present, and if present, how severe. Once begun, the goal of treatment is the same as for acute leukemia: remission, or an arresting of the disease process. There are two phases of treatment for leukemia. The first phase is called induction therapy, in which the main aim is to reduce the number of leukemic cells as much as possible and induce a remission in the patient. Once 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 aim in this case is to kill any remaining cells and to maintain the remission for as long as possible.

---

KEY TERMS

---

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

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

Chemotherapy—Treatment with anticancer drugs.

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.

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 are still present.

---

Chemotherapy

Chemotherapy 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), while 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.

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 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 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 administered to the patient through a needle in a vein to replace the destroyed marrow.

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 save it. The marrow remaining in the patient's body is destroyed with high-dose chemotherapy and radiation therapy. The thawed marrow is returned to the patient intravenously. This mode 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.

Because leukemia cells can spread to all the organs via the bloodstream and the lymph vessels, surgery is not considered an option for treating leukemias.

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. More than half the patients diagnosed with chronic lymphocytic leukemia survive for at least five years due to the slowness of the disease process. Eventual death for CLL patients usually is the result of repeated and overwhelming infections. The out-look for chronic myeloid leukemia is generally less optimistic. Overall, average survival time for CML patients from the time of diagnosis is three years. However, 20% of all CML patients survive for at least 10 years, and bone marrow transplantation is improving the outcome.

Health care team roles

In most cases, a diagnosis of leukemia is made in a physician's office, a general medical clinic, or an emergency room by a primary care practitioner. Children and adolescents with leukemia are likely to be diagnosed by their primary care physician, pediatrician, or pediatric nurse practitioner. Oncologists, specialists in the diagnosis and treatment of cancer, are also often involved.

Hematologists, specialists in the diagnosis and treatment of disorders of the blood and the organs that produce blood cells, may be consulted. A pathologist, a specialist in studying tissue and cell samples, may also assist in diagnosis.

Both registered Nurses (RNs) and licensed practical nurses (LPNs) are often the people who deal the most with leukemia patients both in general hospitals, homes, or other health care facilities. Good supportive nursing care and observation are necessary to:

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

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

Prevention

There is no known way to prevent leukemias. 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