Leukemia

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 34,810 new cases of leukemia will be diagnosed in the United States in 2005. Acute leukemias account for nearly 11 percent more of the cases than chronic leukemias. Most cases occur in older adults; more than half of all cases occur after age 67. Leukemia is expected to strike 9 times as many adults as children in 2004. (About 31,289 adults compared with 3,521 children, ages 0-19). About 30 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 11,960 new cases this year, and chronic lymphocytic leukemia (CLL), with some 9,730 new cases this year. Chronic myelogenous leukemia (CML) is estimated to affect about 4,600 persons this year. Acute lymphocytic leukemia (ALL) will account for about 3,970 cases this year. Other unclassified forms of leukemia account for the 4,550 remaining cases.

Incidence by Gender

Incidence rates for all types of leukemia are higher among males than among females. In 2005, 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 7 percent higher among Americans of African descent than among those of European descent. The incidence rate for all cancers among African Americans, from 1973-2002, was 505.2 per 100,000 population, averaging about 175,093 cases each year.

Leukemia is one of the top 15 most frequently occurring

cancers in minority groups. Leukemia incidence is highest among whites and lowest among American Indians/Alaskan natives.

Leukemia rates are substantially higher for white 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 25 percent of all cancers occurring among children younger than 20 years from 1997-2002. In the 13 SEER areas of the United States, there were 1,490 children under the age of 20 diagnosed with leukemia from 1998-2002, including 1,113 with ALL. From this data, it is estimated that 3,521 children will be diagnosed with leukemia in 2005 throughout the United States. Nearly 2,455 new cases of childhood ALL are expected to occur in 2005.

• 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 10 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 with ALL are cured.

CLL and AML incidence increase dramatically among people who are over the age of 50, and CML incidence increases dramatically among