Leukemia is cancer of the bone marrow and blood. The bone marrow is the soft, inner part of the bones that makes red and white blood cells. Leukemia is characterized by the uncontrolled accumulation of white blood cells (leucocytes).
Under normal circumstances, the blood-forming (hematopoietic) cells of the bone marrow make leukocytes to defend the body against infectious organisms, such as viruses and bacteria. Leukocytes fight infection through a process known as phagocytosis. During phagocytosis, the leukocytes surround and destroy foreign organisms. White blood cells also produce, transport, and distribute antibodies as part of the body's immune response. If some leukocytes are damaged and remain in an immature form, they become poor infection fighters that multiply excessively and do not die off as they should. Immature leukocytes are those that have just been formed in the bone marrow.
These damaged leukemic cells accumulate and lessen the production of oxygen-carrying red blood cells (erythrocytes), blood-clotting cells (platelets), and normal leukocytes. If untreated, the surplus leukemic cells overwhelm the bone marrow, enter the bloodstream, and eventually invade other parts of the body, such as the lymph nodes, spleen, liver, and central nervous system (brain, spinal cord). In this way, the behavior of leukemia is different than that of other cancers, which usually begin in major organs and ultimately spread to the bone marrow.
Leukemia can be acute (fast growing) or chronic (slow growing).
The four major types of leukemia are: acute lymphocytic leukemia (ALL); chronic lymphocytic leukemia (CLL); acute myelogenous leukemia (AML); and chronic myelogenous leukemia (CML).
Leukemia is often thought to be a childhood disease, but statistically, leukemia strikes 10 times more adults than children. The American Cancer Society (ACS) predicts that about 35,070 new leukemia cases will be diagnosed in the United States in 2006. Acute myelogenous leukemia (AML) is the most frequently reported form of leukemia in adults, and approximately 11,930 new cases are anticipated in 2006.
The relative five-year survival rate has more than tripled in the past 47 years for patients with leukemia due to advances in treatment. The overall relative survival rate is nearly 50%. The relative survival rates differ according to the age of the patient at diagnosis, gender, race, and type of leukemia.
It is anticipated that approximately 21,790 deaths in the United States will be attributed to leukemia in 2007 (12,320 males and 9,470 females).
The goal of treatment for leukemia is to bring about a complete remission. Complete remission means that there is no evidence of the disease and the individual returns to good health with normal blood and marrow cells. The cancer is not detectable in remission. Relapse indicates a return of the cancer cells and return of other signs and symptoms of the disease. Treatment centers report increasing numbers of patients with leukemia who are in complete remission at least five years after the diagnosis of their disease.
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types of leukemia
Leukemia is divided into four categories. It can be myelogenous or lymphocytic and acute (fast growing) or chronic (slow growing). Acute leukemia is fast-growing and can overrun the body within a few weeks or months. By contrast, chronic leukemia is slow-growing and progressively worsens over years. The terms myelogenous or lymphocytic denote which type of white blood cell is involved.
Acute myelogenous leukemia (AML): Acute myelogenous leukemia (AML), also called acute nonlymphocytic leukemia, is the most common type of leukemia. AML occurs in children and adults. AML is fast growing and requires aggressive treatment.
Acute lymphocytic leukemia (ALL): Acute lymphocytic leukemia (ALL) is the most common type of leukemia in young children. ALL accounts for 80% of all childhood leukemias. ALL is also fast growing and requires aggressive treatment.
Chronic lymphocytic leukemia (CLL): Chronic lymphocytic leukemia (CLL) is a common adult leukemia. CLL is more common in Jewish people of Russian or Eastern European descent. It almost never affects children. Individuals with CLL may be well for years without treatment.
Chronic myelogenous leukemia (CML): Chronic myelogenous leukemia (CML) is a type of leukemia that mainly affects adults. CML is associated with a chromosome abnormality called the Philadelphia chromosome, which creates an abnormal gene called BCR-ABL. The BCR-ABL gene produces an abnormal protein called tyrosine kinase that doctors and researchers believe causes leukemia cells to grow and develop. Before treatment, an individual with CML may have few or no symptoms for months or years before entering a phase in which the leukemia cells grow more quickly.
Other chronic myeloid disorders: Like CML, this group of diseases causes chronic leukemia by the creation of too few or too many myeloid cells (a type of white blood cell). Chronic myeloid disorders include myelodysplastic syndromes and myeloproliferative disorders such as essential thrombocythemia, polycythemia vera, and myelofibrosis. These conditions may cause fluctuations in white blood cell levels and lead to acute myeloid leukemia (AML).
Acute vs. chronic leukemia: Acute leukemia is a rapidly progressing disease that results in the accumulation of immature leukocytes (white blood cells) in the marrow and blood. The marrow often can no longer produce enough normal red blood cells, white blood cells, and platelets. Anemia, a deficiency of red cells, develops in virtually all leukemia patients. The lack of normal white cells impairs the body's ability to fight infections. A shortage of platelets results in bruising and easy bleeding.
Therefore, acute leukemia needs to be treated immediately; otherwise, the disease may be fatal within a few months. Fortunately, some subtypes of acute leukemia respond very well to available therapies and they are curable. Children often develop acute forms of leukemia, which are managed differently from leukemia in adults.
Chronic leukemia progresses more slowly and allows greater numbers of more mature, functional cells to be made. Unlike acute leukemia, chronic leukemia does not always require treatment. For older adults or people with early-stage CLL and few troublesome symptoms, the risks associated with the disease do not warrant the risks and discomfort associated with treatment, such as nausea, fatigue, and infection. If symptoms change or worsen, the individual can discuss treatment options with their doctor.