Leukemia is a blood-based cancer characterized by the abnormal proliferation and accumulation of immature, functionless blood cells in the blood and marrow, which impede the development and function of normal blood cells. If untreated, the cancerous blood 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.
According to the Leukemia and Lymphoma Society, an estimated 43,050 new cases of leukemia were diagnosed in the United States in 2010, approximately 21,840 people died from the disease, and more than 259,889 people in the U.S. were either living with, or in remission from leukemia. The incidence of hematological cancers, such as leukemias, lymphomas and myelomas, is among the fastest-growing cancers due to the aging population. While most cases occur in older adults (more than half are diagnosed in adults over age 67), leukemia also causes more deaths than any other cancer among children and adults under the age of 20.