Leukemia is a cancer of the blood cells. There are several broad categories of blood cells, including red blood cells (RBCs), white blood cells (WBCs), and platelets. Generally, leukemia refers to cancers of the WBCs.

WBCs are a vital part of your immune system. They protect your body from invasion by:

  • bacteria
  • viruses
  • fungi
  • abnormal cells
  • foreign substances

In leukemia, the WBCs do not function like normal WBCs. They can also divide too quickly and eventually crowd out normal cells.

WBCs are mostly produced in the bone marrow, but certain types of WBCs are also made in the:

Once formed, WBCs travel through your bloodstream and lymphatic vessels to fight infection in the body’s tissues.

The symptoms of leukemia may include:

Leukemia can also cause symptoms in organs that have been infiltrated or affected by the cancer cells. For example, if the cancer spreads to the central nervous system, it can cause:

How the cancer spreads depends on the type of leukemia and how aggressive it is.

Leukemia can also spread to other parts of your body, including the:

The onset of leukemia can be acute (sudden onset) or chronic (slow onset). In acute leukemia, cancer cells multiply quickly. In chronic leukemia, the disease progresses slowly and early symptoms may be very mild.

Leukemia is also classified according to the type of cell that’s affected.

Leukemia involving myeloid cells is called myeloid or myelogenous leukemia. Myeloid cells are immature blood cells that would normally become granulocytes or monocytes.

Leukemia involving lymphocytes is called lymphocytic leukemia.

There are four main types of leukemia:

Acute myeloid leukemia (AML)

Acute myeloid leukemia (AML) can occur in children and adults. According to the Surveillance, Epidemiology, and End Results Program of the National Cancer Institute (NCI), about 20,000 new cases of AML are diagnosed each year in the United States. This is the most common form of leukemia. The 5-year survival rate for AML is 29.5 percent.

Acute lymphocytic leukemia (ALL)

Acute lymphocytic leukemia (ALL) occurs mostly in children. The NCI estimates about 6,000 new cases of ALL are diagnosed annually. The 5-year survival rate for ALL is 69.9 percent.

Chronic myeloid leukemia (CML)

Chronic myeloid leukemia (CML) affects mostly adults. About 9,000 new cases of CML are diagnosed annually, according to the NCI. The 5-year survival rate for CML is 70.6 percent.

Chronic lymphocytic leukemia (CLL)

Chronic lymphocytic leukemia (CLL) is most likely to affect people over age 55. It’s very rarely seen in children. According to the NCI, about 21,000 new cases of CLL are diagnosed annually. The 5-year survival rate for CLL is 87.2 percent.

Hairy cell leukemia is a very rare subtype of CLL. Its name comes from the appearance of the cancerous lymphocytes under a microscope.

Researchers do not know what exactly causes leukemia. However, there are some risk factors for developing this cancer. Some of these risk factors include:

  • previous chemotherapy or radiation for other types of cancers
  • genetic disorders like Down syndrome
  • other blood cancer disorders
  • repeated exposure to the chemical benzene, which is found in cigarette smoke

The causes of leukemia are not currently known. However, several factors that may increase your risk have been identified. These include:

Leukemia is usually treated by a hematologist-oncologist. These are doctors who specialize in blood disorders and cancer. The treatment depends on the type and stage of the cancer. It also depends on the patient’s overall health and other medical conditions.

Some forms of leukemia grow slowly and do not need immediate treatment. However, treatment for leukemia usually involves one or more of the following:

  • Chemotherapy. Chemotherapy uses drugs to kill leukemia cells. Depending on the type of leukemia, you may take either a single drug or a combination of different drugs.
  • Radiation therapy. Radiation therapy uses high-energy radiation to damage leukemia cells and inhibit their growth. Radiation can be applied to a specific area or to your entire body.
  • Stem cell transplantation. A stem cell transplant replaces diseased bone marrow with healthy bone marrow, either your own (called autologous transplantation) or from a donor (called allogeneic transplantation). This procedure is also called a bone marrow transplant.
  • Biological or immune therapy. Biological or immune therapy uses treatments that help your immune system recognize and attack cancer cells.
  • Targeted therapy. Targeted therapy uses medications that take advantage of vulnerabilities in cancer cells. For example, imatinib (Gleevec) is a targeted drug that’s commonly used against CML.

Leukemia may be suspected if you have concerning symptoms or certain risk factors. A doctor will begin by looking at your complete history and performing a physical examination.

However, leukemia cannot be fully diagnosed by a physical exam. Instead, doctors will make a diagnosis using:

A diagnosis is typically confirmed using a bone marrow biopsy and aspiration.

Tests

There are a number of different tests that can be used to diagnose leukemia. A complete blood count determines the numbers of RBCs, WBCs, and platelets in the blood. Looking at your blood under a microscope can also determine if the cells have an abnormal appearance.

Tissue biopsiescan be taken from the bone marrow or lymph nodes to look for evidence of leukemia. These small samples can identify the type of leukemia and its growth rate. Biopsies of other organs, such as the liver and spleen, can show if the cancer has spread.

Staging

Once leukemia is diagnosed, it will be staged. Staging finds out how much the cancer has spread and progressed, and it helps a doctor determine your outlook.

AML and ALL are staged based on how cancer cells look under a microscope and the type of cells involved. ALL and CLL are staged based on the WBC count at the time of diagnosis. The presence of immature white blood cells, or myeloblasts, in the blood and bone marrow is also used to stage AML and CML.

Assessing the progression

A number of other tests can be used to determine the progression of the disease:

  • Flow cytometry examines the DNA of the cancer cells and determines their growth rate.
  • Liver function tests show whether leukemia cells are affecting the liver.
  • Lumbar puncture is performed by inserting a thin needle between the vertebrae of your lower back. This allows your doctor to collect spinal fluid and determine if the cancer has spread to the central nervous system.
  • Imaging tests, such as X-rays, ultrasounds, and CT scans, help doctors look for any damage to other organs that’s caused by the leukemia.

The long-term outlook for people who have leukemia depends on the type of cancer they have and their stage at diagnosis. The sooner leukemia is diagnosed and the faster it’s treated, the better your chance of recovery is.

Some factors, like older age, past history of blood disorders, and chromosome mutations, can negatively affect the outlook.

According to the NCI, the number of leukemia deaths has been falling on average 1.7 percent each year from 2009 to 2018. The 5-year survival rate (or percent of people surviving at least 5 years after receiving a diagnosis) was 65 percent from 2011 to 2017.

However, it’s important to note that this figure includes people of all ages and with all forms of leukemia. It’s not predictive of the outcome for any one person. Work with your medical team to treat leukemia and find out your specific outlook. Remember that each person’s situation is different.

Read this article in Spanish.