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 people who are over the age of 60. 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 45 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 1970-73, the five year relative survival rate had jumped to 22 percent, and in 1995-2001 the overall relative survival rate was 48 percent. The relative survival rates differ by of theT patient at diagnosis, gender, race and type of leukemia. During 1995- 2001 relative survival rates overall were: ?Acute lymphocytic leukemia (ALL): 64. 6 percent overall; 88.
4 percent for children under 5 ? Chronic lymphocytic leukemia (CLL): 74. 2 percent ?Acute myelogenous leukemia (AML): 19. 8 percent overall; 52 percent for children under 15 ? Chronic myelogenous leukemia (CML): 39. 3 percent At the present time there are approximately 198,257 people living with leukemia in the United States. Deaths It is anticipated that approximately 22,570 deaths in the United States will be attributed to leukemia in 2005 (12,540 males and 10,030 females). There will be an estimated 4,600 deaths from chronic lymphocytic leukemia and 1,490 deaths from acute lymphocytic leukemia.
There will be an estimated 9,000 deaths from acute myelogenous leukemia and 850 deaths from chronic myelogenous leukemia. Unclassified forms of leukemia will account for 6,630 additional deaths. ?The estimated numbers of deaths attributed to leukemia in the United States are about 25 percent higher for males than females. The leukemia death rate for children 0-14 years of age in the United States has declined 60 percent over the past three decades. Despite this decline, leukemia causes more deaths than any other cancer among children under age 20. Approximately 413 children from 0-14 years of age are expected to die from leukemia in 2005.