Leukemia

Leukemia is cancer (Read about "Cancer: What It Is") that starts in blood-forming tissue such as the bone marrow and causes large numbers of blood cells to be produced and enter the bloodstream. Bone marrow is the soft, spongy center of bones. When leukemia develops, the body produces large numbers of abnormal blood cells.

The bone marrow makes different types of blood cells. Each type has a special function. White blood cells help fight infection; red blood cells carry oxygen to tissues throughout the body and platelets help form blood clots that control bleeding. The National Cancer Institute (NCI) says that in most types of leukemia, the abnormal cells are white blood cells. The leukemia cells usually look different from normal blood cells, and they do not function properly.

Leukemia causes an accumulation of immature cells in the marrow and blood and as a result, the marrow can no longer produce enough normal red and white blood cells and platelets. According to NCI, this results in such symptoms as:

• anemia (Read about "Anemia")
• paleness and fatigue
• easy bruising
• easy bleeding (Read about "Bleeding Disorders")
• inability to fight infections (Read about "The Immune System")

The American Cancer Society says leukemia can be categorized as chronic or acute. Acute leukemia progresses quickly. NCI says chronic leukemia progresses more slowly and permits greater numbers of more mature, functional cells to be made.

Leukemia is also categorized by the cell type involved, either myelogenous or lymphocytic. Leukemia can arise in either of the two main types of white blood cells - lymphoid cells or myeloid cells. When leukemia affects lymphoid cells, it is called lymphocytic leukemia. When myeloid cells are affected, the disease is called myeloid or myelogenous leukemia. NCI says the most common types of leukemia are:

• Acute lymphocytic leukemia (ALL) is the most common type of leukemia in young children. This disease also affects adults, especially those age 65 and older. ALL is a fast-growing type of leukemia in which too many lymphoblasts (immature white blood cells) are found in the blood and bone marrow. It is also called acute lymphoblastic leukemia.
• Acute myeloid leukemia (AML) occurs in both adults and children. This type of leukemia is sometimes called acute nonlymphocytic leukemia (ANLL). It is a quickly progressing disease in which too many immature white blood cells (not lymphocytes) are found in the blood and bone marrow.
• Chronic lymphocytic leukemia (CLL) most often affects adults over the age of 55. It sometimes occurs in younger adults, but it almost never affects children. This is a slow-growing type of leukemia in which too many lymphoblasts (immature white blood cells) are found in the blood and bone marrow. It is also called chronic lymphoblastic leukemia
• Chronic myeloid leukemia (CML) occurs mainly in adults. A very small number of children also develop this disease. CML is a slowly progressing disease in which too many white blood cells (not lymphocytes) are made in the bone marrow. It is also called chronic myelogenous leukemia or chronic granulocytic leukemia.

There are many other less common types of leukemia, including hairy cell leukemia, a type of chronic leukemia in which the abnormal white blood cells appear to be covered with tiny hairs when viewed under a microscope. There is also a set of conditions called myeloproliferative disorders, which can develop into acute leukemia. Examples of myeloproliferative disorders include chronic myelomonocytic leukemia (CMML), juvenile myelomonocytic leukemia (JMML), chronic neutrophilic leukemia and chronic eosinophilic leukemia. (Read about "Myelodysplastic/Myeloproliferative Diseases")

NCI says no one is sure of the exact causes of leukemia, although chronic exposure to benzene as well as excessive doses of irradiation have been linked to certain cases.

Researchers at the National Institutes of Health do know that survival rates for leukemia have been improving. Five year survival rates have tripled over the last half century. The leukemia death rate for children in the United States has declined 61 percent over the last three decades, according to the Leukemia & Lymphoma Society. Even so, the disease still kills more children under the age of 15 than any other cancer in the United States. (Read about "Cancer & Children") And leukemia isn't just a disease of the young. Adults get leukemia too. In fact, according to the Leukemia & Lymphoma Society more than half of all cases of leukemia occur after age 60. One positive note is that progress is being made in research to find new treatments for leukemia.

Symptoms and diagnosis

Like all blood cells, leukemia cells travel through the body. Depending on the number of abnormal cells and where these cells collect, patients with leukemia may have a number of symptoms. These may include:

• fevers or night sweats
• frequent infections
• feeling weak or tired
• headache, joint pain (Read about "Headaches")
• bleeding and bruising easily
• swelling or discomfort in the abdomen from an enlarged spleen (Read about "The Spleen")
• swollen lymph nodes (Read about "The Lymph System")

These symptoms can indicate a number of other problems, so it is important to see your doctor if you are having these symptoms. Some of the tests that can be used to diagnose leukemia include blood tests. (Read about "Complete Blood Count") The doctor may also remove some bone marrow from the hipbone or another large bone for examination by a pathologist. (Read about "Biopsy") The doctor may also perform a spinal tap. In this procedure, the doctor removes some of the cerebrospinal fluid (the fluid that fills the spaces in and around the brain and spinal cord). (Read about "The Brain") NCI says the procedure takes about 30 minutes and is performed with local anesthesia. (Read about "Anesthesia") The patient must lie flat for several hours afterward to keep from getting a headache. The lab checks the fluid for leukemia cells or other signs

Treatment

Leukemia affects the bone marrow. Unlike most other cancers, there is no solid tumor to be removed by surgery. Since leukemia is not a single disease but rather a group of diseases, ACS says treatment options for each patient are based on the type of leukemia and how advanced it is. Treatment options can include:

• Chemotherapy - Chemotherapy is the major type of treatment for leukemia. In chemotherapy, strong chemicals are used to kill the leukemia cells. The drugs may be taken orally or they may be injected into a vein. During chemotherapy, many healthy cells may be destroyed, in addition to the cancer cells. For some people, hospitalization is needed during the initial chemotherapy treatments, because of the risk of anemia (Read about "Anemia"), infection and bleeding.
• Biological therapy or immunotherapy - Biological therapy uses substances to improve your immune system's response to cancer. These treatments try to use the body's own immune system (Read about "The Immune System"), either directly or indirectly, to help fight the cancer. The Leukemia and Lymphoma Society says these types of therapies can spare more healthy cells and be less toxic than standard chemotherapy and radiation therapy.
• Kinase inhibitors - This class of drugs is the first type of therapy for some types of leukemia. For people with CML, this class of drugs can inhibit specific proteins in cancer cells that cause the cancer cells to grow and multiply.
• Radiation therapy - Radiation therapy uses x-rays or other high-energy rays to damage leukemia cells and stop their growth. Radiation may be directed at a specific area of the body or it may be directed to the entire body. Radiation can be used in cases where cancer cells have spread to the central nervous system. (Read about "Nervous System") Radiation therapy can also be used in conjunction with bone marrow transplant.
• Stem cell transplant - In stem cell transplant, cells are collected from stem cells that circulate in the bloodstream (peripheral blood). Chemotherapy may also be used in conjunction with stem cell transplantation. (Read about "Transplants") Stem cells are collected from either the patient or a donor. The patient is then given very high doses of chemotherapy, after which the stored stem cells are given to the patient as a blood transfusion. The hope is that they settle in the patient's bone marrow and start to grow and produce blood cells.
• Bone marrow transplant - In a bone marrow transplant, you get high doses of chemotherapy or radiation therapy to first destroy the cancer-producing blood marrow. The marrow is then replaced with healthy bone marrow.

All cases of leukemia are different and no one course of treatment is appropriate for everyone. (Read about chemotherapy, radiation and other cancer therapies in "Cancer Treatments") And while side effects of any cancer treatment can be severe, there is some encouraging news in the fact that five-year survival rate for leukemia patients has tripled since the 1960's. For leukemia, a complete remission that lasts five years after treatment often indicates a cure. The Leukemia and Lymphoma Society says this decline in mortality reflects strides being made in research and treatment of the disease.

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For a list of individual types of cancer, see Cancer: What It Is

Related Information:

    Blood Disorders Glossary