Cancer InDepth: Leukemia
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Leukemia is a malignant disorder that inhibits the normal production of blood cells. The word cancer refers to diseases in which certain cells in the body become abnormal and grow unchecked. In this case, the abnormal cells are blood cells and their precursors. Leukemic cells often do not function normally and cannot do what normal blood cells do.
The bone marrow produces blood cells. White blood cells help the body fight infections. Red blood cells carry oxygen to the tissues. Platelets help the blood clot.
White Blood Cells
When a person has leukemia, the development process of precursor (immature) blood cells stops but the precursor cells are still released into the circulation. Therefore, leukemia is a combination of having too few mature functioning blood cells and too many immature cells, circulating in the blood. Leukemia progresses at different rates. The faster developing forms of the disease are called acute leukemias. The slower are called chronic leukemias. With acute disease, numerous immature cells that do not properly function are found in the blood and bone marrow. With chronic disease, mature cells are still made in large enough numbers to allow the patient to be relatively asymptomatic for many months or years.
Types of Leukemia
The four most common types of leukemia are listed here:
Acute Myelogenous Leukemia (AML) – The cancer begins in immature granulocytic blood cells and progresses very quickly. This type occurs in both adults and children. It is sometimes called acute myelocytic leukemia, acute myeloid leukemia, acute granulocytic leukemia, or acute nonlymphocytic leukemia.
Acute Lymphocytic Leukemia (ALL) – The cancer begins in immature lymphocytic blood cells and progresses very quickly. This is the most common form of childhood leukemia and is highly curable in children. When it affects adults, it is an aggressive disease. It is sometimes called acute lymphocytic anemia or acute lymphoid anemia.
Chronic Myelogenous Leukemia (CML) – The cancer begins in more mature granulocytic blood cells and progresses gradually. This occurs mainly in adults, but may occur in a very small number of children. It is sometimes called chronic myeloid leukemia or chronic granulocytic leukemia. It is associated with a specific molecular event, the formation of the Philadelphia Chromosome and the activation of an enzyme that is now the target of a new drug called STI-571 (Gleevec).
Chronic Lymphocytic Leukemia (CLL) – The cancer begins in more mature lymphocytic blood cells and progresses gradually. This type most often occurs in adults over age 55. It sometimes occurs in younger adults, but rarely occurs in children. It is sometime called chronic lymphoid leukemia.
Who Is Affected
Leukemia affects both adults and children. According to the American Cancer Society, this year approximately 30,800 Americans will learn that they have leukemia; about 21,700 people will die from it. Leukemia is the leading cause of cancer deaths among women under age 20 and men younger than 40. Fewer children are dying of leukemia than in years past. However, leukemia remains the leading cause of cancer deaths among children younger than age 15. About 670 children died of leukemia in 2002.
About 8,800 people died of acute forms of leukemia in 2002. Acute myelogenous leukemia is the most common adult leukemia. About 10,600 people will be diagnosed with this form of the disease this year. The average age of patients with AML is 65. More men than women develop this form of leukemia.
Acute lymphocytic leukemia is more common among children than adults; most patients are younger than 10. About 3,800 people will learn they have ALL this year. Acute forms of leukemia can remain in remission for long periods of time.
About 11,400 people will develop a chronic form of leukemia this year. There will be about 7,000 new cases of chronic lymphocytic leukemia and 4,400 cases of chronic myelogenous leukemia. The chronic forms of the disease mostly strike adults. The average age for patients with chronic lymphocytic leukemia is about 70. Age 40 to 50 is more typical for chronic myelogenous leukemia. Children represent only 2% of chronic leukemia patients.
Causes and Complications
The cause of leukemia is unknown. Researchers have found genetic changes that may be responsible. What causes these genetic mutations remains under investigation. Studies show that certain risk factors are associated with the disease. These include smoking and exposure to radiation or toxins.
Because leukemia affects the blood, complications of the disease typically relate to problems with blood function. Complications of the blood include the following:
- Anemia, which is a lack of red blood cells and produces fatigue.
- Fatigue, which occurs when the cells do not receive enough oxygen, because there are not enough cells to carry oxygen.
- Susceptibility to infection, because there are not enough white cells to fight bacteria, viruses, and other microbes.
- Easy bleeding, which can occur when there are not enough platelets to help with blood clotting.
Leukemia or its treatment can affect the lungs, kidneys, and other systems. Leukostasis, the clumping of white blood cells, can occur as a complication of leukemia and affect the brain, if cancer cells collect in the nervous system. Tumor lysis syndrome is another potential complication of leukemia treatment. It occurs with the death of cancer cells. This may affect multiple organ systems and blood chemistry levels. Kidney failure may occur. Patients may experience pain, cramps, seizures, sudden death, and other problems. Disseminated coagulation, a condition where blood clotting proteins are consumed rapidly leading to both excessive bleeding and blood clotting, is a complication of several of the acute leukemias, particularly acute promyelocytic leukemia, a type of myeloid leukemia.
AML may involve the central nervous system or the eyes, requiring treatment specific to reduce symptoms in these areas.
This Report Covers the Following:
National Cancer Institute
American Cancer Society
The Leukemia & Lymphoma Society
Bast R, et al. Cancer Medicine e5 . Hamilton, Ontario: B.C. Decker Inc.; 2000.
Last reviewed February 2003 by
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