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Board of Directors:

James Chang
Kevin Ching M.D.
Sharon Lau
Stella Lee Leong

What is Leukemia?

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(Copyright 2007 The Leukemia & Lymphoma Society)

Leukemia* is a malignant disease (cancer) of the bone marrow and blood. It is characterized by the uncontrolled accumulation of blood cells. Leukemia is divided into four categories: myelogenous or lymphocytic, each of which can be acute or chronic. The terms myelogenous or lymphocytic denote the cell type involved. Thus, the four major types of leukemia are:

  • Acute Lymphocytic Leukemia
  • Chronic Lymphocytic Leukemia
  • Acute Myelogenous Leukemia
  • Chronic Myelogenous Leukemia

Acute leukemia is a rapidly progressing disease that results in the accumulation of immature, functionless 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.

Chronic leukemia progresses more slowly and allows greater numbers of more mature, functional cells to be made.

New Cases

An estimated 44,240 new cases of leukemia will be diagnosed in the United States in 2007. Chronic leukemias account for 7 percent more cases than acute leukemias. Most cases occur in older adults; more than half of all cases occur after age 67. Leukemia is expected to strike 10 times as many adults as children in 2007. (About 40,440 adults compared with 3,800 children, ages 0-19). About 33 percent of cancers in children ages 0-14 years are leukemia. The most common form of leukemia among children under 19 years of age is Acute Lymphocytic Leukemia (ALL).

The most common types of leukemia in adults are acute myelogenous leukemia (AML), with an estimated 13,410 new cases this year, and chronic lymphocytic leukemia (CLL), with some 15,340 new cases this year. Chronic myelogenous leukemia (CML) is estimated to affect about 4,570 persons this year. Acute lymphocytic leukemia (ALL) will account for about 5,200 cases this year. Other unclassified forms of leukemia account for the 5,720 remaining cases.

Incidence by Gender

Incidence rates for all types of leukemia are higher among males than among females. In 2007, males are expected to account for more than 56 percent of the cases of leukemia. (Note: Incidence rates are the number of new cases in a given year not counting the pre-existing cases. The incidence rates are usually presented as a specific number per 100,000 population.)

Incidence by Race and Ethnicity

Incidence rates for all types of cancer are 5 percent higher among Americans of African descent than among those of  European descent. The incidence rate for all cancers among African Americans, from 2000-2004, was 504 per 100,000 population, averaging about 189,922 cases each year.

Leukemia is one of the top 15 most frequently occuring cancers in minority groups. Leukemia incidence is highest among whites and lowest among American Indians/Alaskan natives.

Leukemia rates are substantially higher for Hispanic, American Indian/Alaskan natives white and Asian/Pacific islander children than for black children. Hispanic children of all races under the age of 20 have the highest rates of leukemia.

Incidence by Age Group

Incidence rates by age differ for each of the leukemias. The leukemias represented 27 percent of all cancers occurring among children younger than 20 years from 2000-2004. In the 17 SEER areas of the United States, there were 4,799 children under the age of 20 diagnosed with leukemia from 2001-2004, including 3,619 with ALL.  It is estimated that in 2007, 3,800 children will be diagnosed with leukemia throughout the United States. About 2,790 new cases of childhood ALL are expected to occur in 2007.

  • The most common form of leukemia among children under 19 years of age is ALL. The incidence of ALL among 1- to 4-year-old children is more than 9 times greater than the rate for young adults ages 20-24.
  • There is optimism within centers that specialize in the treatment of children because survival statistics have dramatically improved over the past 30 years. Most children under 15 with ALL are cured.

CLL incidence increases dramatically among people who are age 50 and older, and AML and CML incidence increase dramatically among people who are age 60 and older. These cancers are most prevalent in the seventh, eighth and ninth decades of life.

Signs and Symptoms

Signs of acute leukemia may include easy bruising or bleeding (as a result of platelet deficiency), paleness or easy fatigue (as a result of anemia), recurrent minor infections or poor healing of minor cuts (because of inadequate white cell count).

These symptoms and signs are not specific to leukemia and may be caused by other disorders. They do, however, warrant medical evaluation. A proportion of people with chronic leukemia may not have major symptoms and are diagnosed during a periodic medical examination. The diagnosis of leukemia requires examination of the cells in blood or marrow.

Possible Causes

Anyone can get leukemia. Leukemia affects all ages and sexes. The cause of leukemia is not known. Chronic exposure to benzene in the workplace and exposure to extraordinary doses of irradiation can be causes of the disease, although neither explains most cases.

Treatment

The aim of treatment is to bring about a complete remission. Complete remission means that there is no evidence of the disease and the patient returns to good health with normal blood and marrow cells. Relapse indicates a return of the cancer cells and return of other signs and symptoms of the disease. For acute leukemia, a complete remission (no evidence of disease in the blood or marrow) that lasts five years after treatment often indicates cure. Treatment centers report increasing numbers of patients with leukemia who are in complete remission at least five years after diagnosis of their disease.

Survival

The relative five-year survival rate has more than tripled in the past 47 years for patients with leukemia. In 1960-63, when compared to a person without leukemia, a patient had a 14 percent chance of living five years.  By 1975-77, the five year relative survival rate had jumped to 35 percent, and in 1996-2003 the overall relative survival rate was  nearly 50 percent. The relative survival rates differ by the age of the patient at diagnosis, gender, race and type of leukemia.

During 1996- 2003 relative survival rates overall were:

  • Acute lymphocytic leukemia (ALL): 65.3 percent overall; 90.4 percent for children under 5
  • Chronic lymphocytic leukemia (CLL): 74.8 percent
  • Acute myelogenous leukemia (AML): 20.7 percent overall; 54.1 percent for children under 15
  • Chronic myelogenous leukemia (CML): 44.4 percent

At the present time there are approximately 218,659 people living with leukemia in the United States.

Deaths

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).

There will be an estimated 4,500 deaths from CLL and 1,420 deaths from ALL. There will be an estimated 8,990 deaths from AML and 490 deaths from CML. Unclassified forms of leukemia will account for 6,390 additional deaths.

The estimated numbers of deaths attributed to leukemia in the United States are about 30 percent higher for males than females.

The leukemia death rate for children 0-14 years of age in the United States has declined 70 percent over the past three decades. Despite this decline, leukemia causes more deaths than any other cancer among children under age 20. About 515 children under the age of 14 are expected to die from leukemia in 2007.

Get More Information

Further details of treatment and supportive care and the beneficial and adverse effects of treatment may be obtained from the Society's booklets on acute myelogenous, acute lymphocytic, chronic myelogenous and chronic lymphocytic and fact sheets on hairy cell leukemia and the chronic myelomonocytic leukemias.

Read or order the The Leukemia & Lymphoma Society's free publications on the specific types of leukemia, lymphoma and myeloma.

* Leukemia facts and statistics from Leukemia, Lymphoma, Myeloma, Facts 2007-2008, June 2007. (In press.)