Leukemia is a form of cancer that affects the body's ability to make healthy blood cells. It starts in the bone marrow, the soft center of various bones. This is where new blood cells are made. Blood cells include:
- Red blood cells, which carry oxygen from the lungs to the body's tissues and take carbon dioxide to the lungs to be exhaled
- Platelets, which help blood clot
- White blood cells, which help fight infections, viruses, and diseases
Although cancer can affect red blood cells and platelets, leukemia generally refers to cancer of the white blood cells. The disease usually affects one of the two major types of white blood cells: lymphocytes and granulocytes. These cells circulate throughout the body to help the immune system fight off viruses, infections, and other invading organisms. Leukemias arising from lymphocytes are called lymphocytic leukemias; those from granulocytes are called myeloid, or myelogenous, leukemias.
Leukemia is either acute (comes on suddenly) or chronic (lasts a long time). Also, the type of leukemic cell determines whether it is an acute leukemia or chronic leukemia. Chronic leukemia rarely affects children; acute leukemia affects adults and children.
Leukemia accounts for about 2% of all cancers. Men are more likely to develop the disease than women, and whites are more likely to develop it than people of other racial or ethnic groups. Adults are much more likely to develop leukemia than children. In fact, leukemia occurs most often in elderly people. When the disease occurs in children, it generally happens before age 10.
Leukemia has several possible causes. These include:
- Exposure to radiation and chemicals such as benzene (found in unleaded gasoline) and other hydrocarbons
- Exposure to agents used to cure or control other cancers, including radiation
- Certain genetic abnormalities, such as Down syndrome
Leukemia is not believed to be inherited; most cases occur in people without any family history of the disease. However, some forms of leukemia, such as chronic lymphocytic leukemia, occasionally strike close relatives in the same family. But most of the time, no specific cause can be identified.
With acute leukemia, immature white blood cells multiply quickly in the bone marrow. Over time, they crowd out healthy cells. (Patients may notice that they bleed a lot or suffer from infections as a result.) When these cells reach high numbers, they can sometimes spread to other organs, causing damage. This is especially true in acute myeloid leukemia. The two main types of acute leukemia involve different types of blood cells:
- Acute lymphocytic leukemia (ALL) is the most common type of leukemia in children, mainly affecting those under age 10. Adults sometimes develop ALL, but it is rare in people older than 50. ALL occurs when primitive blood-forming cells called lymphoblasts reproduce without developing into normal blood cells. These abnormal cells crowd out healthy blood cells. They can collect in the lymph nodes and cause swelling.
- Acute myeloid leukemia (AML) accounts for half of leukemia cases diagnosed in teenagers and in people in their 20s. It is the most common acute leukemia in adults. AML occurs when primitive blood-forming cells called myeloblasts reproduce without developing into normal blood cells. Immature myeloblasts crowd the bone marrow and interfere with the production of normal blood cells. This leads to anemia, a condition in which a person does not have enough red blood cells. It can also lead to bleeding and bruising (due to a lack of blood platelets, which help the blood to clot) and frequent infections (due to a lack of protective white blood cells).
Both ALL and AML have multiple subtypes. The treatment and prognosis may vary somewhat, depending on the subtype.
Chronic leukemia is when the body produces too many blood cells that are only partially developed. These cells often cannot function like mature blood cells. Chronic leukemia usually develops more slowly and is a less dramatic illness than acute leukemia. There are two main types of chronic leukemia:
- Chronic lymphocytic leukemia (CLL) is rare in people under age 30. It is more likely to develop as a person ages. Most cases occur in people between ages 60 and 70. In CLL, abnormal lymphocytes cannot fight infection as well as normal cells can. These cancerous cells live in the bone marrow, blood, spleen, and lymph nodes. They can cause swelling, which appears as swollen glands. People with CLL can live a long time, even without treatment. Most often, CLL is discovered when a person has a routine blood test that shows elevated levels of lymphocytes. Over time, this type of leukemia can require treatment, especially if the person has infections or develops a high white blood cell count.
- Chronic myeloid leukemia (CML) occurs most often in people between ages 25 and 60. In CML, the abnormal cells are a type of blood cell called myeloid cells. CML usually involves a defective string of DNA called the Philadelphia chromosome. (This disease is not inherited; the change in DNA that causes it occurs after birth.) The genetic defect results in the production of an abnormal protein. Drugs called tyrosine kinase inhibitors block the function of this abnormal protein, improving a person's blood counts. In some cases, the abnormal genetic defect even seems to disappear. Alternatively, some cases of CML can be cured with a bone marrow transplant.
Both CLL and CML have subtypes. They also share some characteristics with other forms of leukemia. The treatment and prognosis may vary depending on the subtype.
Rarer forms of leukemia
Lymphatic and myelogenous leukemias are the most common. However, cancers of other types of bone marrow cells can develop. For example, megakaryocytic leukemia arises from megakaryocytes, cells that form platelets. (Platelets help blood to clot.) Another rare form of leukemia is erythroleukemia. It arises from cells that that form red blood cells. Like chronic and acute leukemias, rare forms of the disease can be categorized into subtypes. The subtype depends on what markers the cells carry on their surface.
Early symptoms of leukemia include:
- Aching bones or joints
- Skin rashes
- Swollen glands (lymph nodes)
- Unexplained weight loss
- Bleeding or swollen gums
- An enlarged spleen or liver, or a feeling of abdominal fullness
- Slow-healing cuts, nosebleeds, or frequent bruises
Many of these symptoms accompany the flu and other common medical problems. If you have any of these symptoms, see your doctor. He or she can diagnose the problem.
Your doctor may not suspect leukemia based on your symptoms alone. However, during your physical examination, he or she may find that you have swollen lymph nodes or an enlarged liver or spleen. Routine blood tests, especially blood cell counts, may yield abnormal results.
At this point, your doctor may order other tests, including:
- A bone marrow biopsy (a sample of bone marrow is removed and examined)
- More blood tests, to check for abnormal cells
- Tests for genetic abnormalities, such as the Philadelphia chromosome
Genetic tests can help determine exactly what type of leukemia you have. (Each of the four main types has subtypes.) These sophisticated tests may also offer clues as to how you will respond to a particular therapy.
In general, chronic leukemia progresses more slowly than acute leukemia. Without drugs called tyrosine kinase inhibitors or a bone marrow transplant, people with CML can live for several years until the disease acts like AML. Whether tyrosine kinase inhibitors can delay or prevent the transformation of a chronic leukemia to an acute leukemia remains to be seen.
There is no way to prevent most forms of leukemia. In the future, genetic testing may help identify people who are more likely to develop the illness. Until then, close relatives of people with leukemia should have routine physical exams.
The treatment of leukemia is among the most intensive of all cancer therapies. Leukemia is a cancer of the bone marrow. This is the place in the body that manufactures most of the body's disease fighting cells. The treatment of leukemia wipes out these cells along with the cancer cells.
Treatment often severely compromise immune function and the body's ability to fight infection. Patients need a tremendous amount of supportive care to recover fully. That's why people with this disease should be treated in medical centers that routinely care for leukemia patients and that provide excellent supportive care, especially during periods of immune suppression.
Unlike other cancers, the treatment of acute leukemia does not depend on how far the disease has advanced but on the person's condition. Has the person just been diagnosed with the disease? Or has the disease come back after remission (a period when the disease is controlled)?
With ALL, treatment generally occurs in phases. However, not all patients experience all of these phases:
- Phase 1 (induction therapy) uses chemotherapy in the hospital to try to control the disease.
- Phase 2 (consolidation) continues chemotherapy, but on an outpatient basis, to keep the disease in remission. This means that person returns to the hospital for treatment, but does not stay overnight.
- Phase 3 (prophylaxis) uses different chemotherapy drugs to prevent the leukemia from entering the brain and central nervous system. Chemotherapy may be combined with radiation therapy.
- Phase 4 (maintenance) involves regular physical exams and laboratory tests after the leukemia has been treated to be sure that it has not returned.
- Recurrent ALL uses different doses of various chemotherapy drugs to combat the disease if it returns. People may need several years of chemotherapy to keep the leukemia in remission. Some people may receive a bone marrow transplant.
With AML, treatment generally depends on the patient's age and overall health. It also depends on the patient's blood cell counts. As with ALL, treatment usually begins with induction therapy in an effort to send the leukemia into remission. When leukemia cells can no longer be seen, consolidation therapy begins. Bone marrow transplantation may also be considered in the treatment plan.
To treat CLL, your doctor must first determine the extent of the cancer. This is called staging. There are five stages of CLL:
- Stage 0. There are too many lymphocytes in the blood. Generally, there are no other symptoms of leukemia.
- Stage I. The lymph nodes are swollen because there are too many lymphocytes in the blood.
- Stage II. The lymph nodes, spleen, and liver are swollen because there are too many lymphocytes.
- Stage III. Anemia has developed because there are too few red blood cells in the blood.
- Stage IV. There are too few platelets in the blood. The lymph nodes, spleen, and liver may be swollen. Anemia may be present.
Treatment of CLL depends on the stage of the disease, as well as on the person's age and overall health. In stage 0, treatment may not be needed, but the person's health will be monitored closely. In stage I or II, observation (with close monitoring) or chemotherapy is the usual treatment. In Stage III or IV, intensive chemotherapy with one or more drugs is the standard treatment. Some people may need a bone marrow transplant.
For CML, tyrosine kinase inhibitors have become standard therapy, especially for people in the early stage of the disease. Whether a bone marrow transplant is done depends on the stage of the disease, the person's health, and whether a suitable bone marrow donor is available.
The use of targeted therapies has dramatically changed the prognosis for many people with CML. Patients can live for prolonged periods of time with these medicines. They specifically correct the chemical defects in the cancer cells that had allowed them to grow in an uncontrollable fashion.
Call your doctor if you have any symptoms of leukemia. These might include:
- Abnormal bruising or bleeding
- Persistent swollen glands
- Unexplained weight loss
- Persistent fever
- Persistent fatigue
If you are diagnosed with leukemia, consider transferring your care to a specialized cancer center.
Long-term survival of leukemia varies greatly, depending upon multiple factors, including type of leukemia and age of the patient.
- ALL: In general, the disease goes into remission in nearly all children who have it. More than 4 out of 5 children live at least 5 years. The prognosis for adults is not as good. Only 25% to 35% of adults live 5 years or longer.
- AML: With proper treatment, most people with this cancer can expect to go into remission. About 80% who go into remission will do so within 1 month of induction therapy. In some people, however, the disease will return, lowering the cure rate.
- CLL: On average, people with this cancer survive 9 years, although some have lived for decades. Remission occurs in most people with stage I or II disease who are treated with chemotherapy, although the cancer always comes back at some point.
- CML: The outlook for people with chronic myeloid leukemia has improved dramatically over the past 10 years. Survival rates of over 5 years in people treated with a tyrosine kinase inhibitor have been reported to be as high as 90%.
The Leukemia and Lymphoma Society
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National Cancer Institute (NCI)
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American Cancer Society (ACS)
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American Academy of Pediatrics (AAP)
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National Institute of Child Health and Human Development
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