Merck Manual

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Overview of Leukemia

By

Ashkan Emadi

, MD, PhD, University of Maryland;


Jennie York Law

, MD, University of Maryland

Last full review/revision May 2020| Content last modified May 2020
Click here for the Professional Version
Topic Resources

Leukemias are cancers of white blood cells or of cells that develop into white blood cells.

White blood cells develop from stem cells in the bone marrow. Sometimes the development goes awry, and pieces of chromosomes get rearranged. The resulting abnormal chromosomes interfere with normal control of cell division, so that affected cells multiply uncontrollably or are resistant to normal cell death, resulting in leukemia.

Classification

Leukemias are grouped into four main types:

The types are defined according to how quickly they progress and the type and characteristics of the white blood cells that become cancerous.

Acute leukemias progress rapidly and consist of immature cells.

Chronic leukemias progress slowly and consist of more mature cells.

Lymphocytic leukemias develop from cancerous changes in lymphocytes or in cells that normally produce lymphocytes.

Myeloid (myelocytic, or myelogenous) leukemias develop from cancerous changes in cells that normally produce neutrophils, basophils, eosinophils, and monocytes.

Complications

Leukemia cells ultimately occupy the bone marrow, replacing or suppressing the function of cells that develop into normal blood cells. This interference with normal bone marrow cell function can lead to inadequate numbers of:

  • Red blood cells (causing anemia)

  • Normal white blood cells (increasing the risk of infection)

  • Platelets (increasing the risk of bleeding)

Leukemia cells may also invade other organs, including the liver, spleen, lymph nodes, testes, and brain.

Causes

The cause of most types of leukemia is not known. Exposure to radiation, to some types of chemotherapy, or to certain chemicals (such as benzene, some pesticides, and chemicals in tobacco smoke) increases the risk of developing some types of leukemia, although leukemia develops only in a very small number of exposed people. Certain hereditary disorders, such as Down syndrome and Fanconi anemia, increase the risk as well. In some people, leukemia is caused by certain abnormalities of the chromosomes.

A virus known as human T lymphotropic virus 1 (HTLV-1), which is similar to the virus (HIV-1) that causes AIDS, is strongly suspected of causing a rare type of lymphocytic leukemia called adult T-cell leukemia. Infection with the Epstein-Barr virus (which also causes mononucleosis) has been associated with a rare form of lymphocytic leukemia that occurs in Asia and Africa.

Treatment

  • Drugs, usually chemotherapy, immunotherapy, and/or targeted therapy

  • Sometimes stem cell transplantation, radiation therapy, or surgery

Many leukemias can be effectively treated, and some can be cured. Treatment can consist of different types of drugs called

  • Chemotherapy: Chemotherapy consists of drugs that kill dividing cells. Chemotherapy therefore attacks cancer cells because they divide rapidly, but it also can harm normal cells.

  • Immunotherapy: Immunotherapy is a cancer treatment that uses a person's own immune system to kill cancer cells.

  • Targeted therapy: Targeted therapy consists of drugs that attack a cancer cell's innate biologic mechanisms.

Both immunotherapy and targeted therapy are less likely to kill normal cells than chemotherapy does and are, therefore, better tolerated. Doctors select the particular drug or combination of drugs based on the classification of the leukemia. Sometimes, stem cell transplantation, radiation therapy, or surgery is used.

The complications of leukemia may require treatment. People may need blood transfusions if leukemia has caused severe anemia. They may need antibiotics if infections develop. If bleeding occurs, they may need platelet transfusions.

When leukemia is under control, the number of abnormal cells in the bone marrow is very low, and people are said to be in remission. If numbers of leukemia cells increase again, people are said to have a relapse.

For some people in relapse, quality of life eventually deteriorates, and the potential benefit for further treatment may be extremely limited. Keeping people comfortable may become more important than trying to modestly prolong life. Affected people and their family members must be involved in these decisions. Much can be done to provide compassionate care, relieve symptoms, and maintain dignity.

More Information

The following is an English-language resource that may be useful. Please note that the MANUAL is not responsible for the content of this resource.

NOTE: This is the Consumer Version. DOCTORS: Click here for the Professional Version
Click here for the Professional Version
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