An estimated 27,000 new cases of leukemia are diagnosed annually. Leukemia is a cancer of the blood and bone marrow. Bone marrow is the sponge-like material found inside the large bones in the body. Bone marrow makes white blood cells (to prevent infection), platelets (to make the blood clot) and red blood cells (to carry oxygen and other materials to various parts of the body). Immature cells produced by the bone marrow are called blasts. In leukemia, blasts may fail to develop into mature cells, or they may not mature correctly.

Depending on the type of cells affected by the disease, the patient may develop one of four major types of leukemia: acute myelogenous leukemia (AML), acute lymphocytic leukemia (ALL), chronic myelogenous leukemia (CML) or chronic lymphocytic leukemia (CLL). Leukemia can be generally divided into two groups, acute and chronic.

In acute leukemia, the disease spreads quickly as many undeveloped malignant blasts replace normal cells in the blood and marrow. The cancerous cells eventually stop producing red blood cells, white blood cells and/or platelets. The patient becomes anemic and gets infections. Having too few platelets prevents injuries from healing and makes the patient bleed easily.

In chronic leukemia, the disease grows slowly and many more mature-looking cancer cells are found. A patient with chronic leukemia does not experience the same symptoms as the patient with acute leukemia, and treatment for the two kinds of leukemia is different.

In its early stages, the disease may not cause any symptoms at all. However, the following are possible signs of leukemia

• Flu or cold symptoms
• Tiredness and shortness of breath when exerting physical effort
• Pale complexion from anemia
• Signs of bleeding caused by a very low platelet count, including black and blue marks occurring for no reason or because of a minor injury; pinhead-sized spots appearing under the skin (petechiae); or prolonged bleeding from minor cuts
• Mild fever, swollen gums, frequent minor infections like pustules or sores in the anal area
• Slow healing of cuts
• Discomfort in bones or joints
• Enlarged liver and spleen

The causes of most forms of leukemia are not known. Researchers believe the disease is due to complex interactions between genetic factors and the environment. Certain viruses are also suspected as promoting leukemia. The disease is not considered contagious or inherited. Risk factors include:

• Certain types of work may cause leukemia due to constant exposure to hazardous materials. Included are farmers involved in high levels of soybean production, cattle ranching, dairy production and herbicide use; rubber manufacturing workers; asbestos workers and tire repair workers.
  
  
• Certain drugs used to treat other forms of cancers like breast cancer, ovarian cancer or lymphoma
  
• Exposure to certain chemicals, such as benzene and some types of pesticides
  
• Exposure to high doses of high-energy X-rays (radiation)
  

The doctor may order blood counts for signs of leukemia. If red blood cell and platelet counts are low and suspicious blast cells can be seen, the doctor may perform a bone marrow biopsy. While the patient is under anesthesia, a large needle is inserted into the bone to remove a small amount of bone marrow. This is examined for the presence of abnormal blast cells, and the biopsy may find defects in genetic materials (chromosomes) linked to certain types of leukemia (for example, Philadelphia chromosome in CML). The doctor will then be able to determine the type of leukemia present and design a plan for the most effective treatment.

The approach to treating leukemia is different for each major type of leukemia.

• Biologic therapy
• Blood and marrow transplantation
• Chemotherapy
• Radiation therapy

• Samuel Oschin Comprehensive Cancer Institute
• Cedars-Sinai Outpatient Cancer Center
• Blood and Marrow Transplant Program