Leukemia is referring to as the cancer of the blood or bone marrow. Bone marrow manufactures blood cells. Leukemia can occur when there is an issue with the manufacturing of blood cells. It is normallty affects the leukocytes, or white blood cells.It is most common to the people over the age of 55 years, but it is also the most common cancer in those aged less than 15 years. There's really nothing you can do to prevent leukemia. It's cancer of your blood cells caused by a high in the number of white blood cells in your body. They crowd out the red blood cells and platelets your body needs to be healthy. All those extra white blood cells don't work right, and that causes problems.