Leukemia is a cancer of the cells in the blood. It usually involves the various forms and stages of the white blood cells , although on rare occasions it may involve red blood cells and platelets.
Leukemia is often thought of as primarily a childhood disease, but it strikes many more adults than children. Adults account for 25,000 of the estimated 28,600 new cases expected in the United States in 1994. Acute leukemia is the most common childhood malignancy. The incidence of leukemia has not changed dramatically over the past 50 years, but survival rates for some forms of the disease have improved, especially in children, with the development of new types of treatment and chemotherapy agents. With acute lymphocytic leukemia in adults, for example, the five-year survival has increased from 4 percent in the early 1960s to about 50 percent today. More than half of the children who develop acute lymphocytic leukemia are alive five years after diagnosis, the majority being considered cured.
Types The many different forms of leukemia are generally divided into acute or chronic and then classified according to the cell type involved. There are two major types of white blood cells—granulocytic (myeloid)
