Leukemia is a cancer of the blood or bone marrow. Bone marrow produces blood cells. Leukemia can develop due to a problem with blood cell production. It usually affects the leukocytes, or white blood cells.
The National Cancer Institute estimates that 61,780 people will receive a diagnosis of leukemia in 2019. They also predict that leukemia will cause 22,840 deaths in the same year.
Acute leukemia develops quickly and worsens rapidly, but chronic leukemia gets worse over time. There are several different types of leukemia, and the best course of treatment and a person's chance of survival depends on which type they have.
In this article, we provide an overview of leukemia, causes, treatment, type, and symptoms.
Leukemia develops when the DNA of developing blood cells, mainly white cells, incurs damage. This causes the blood cells to grow and divide uncontrollably.
Healthy blood cells die, and new cells replace them. These develop in the bone marrow.
The abnormal blood cells do not die at a natural point in their life cycle. Instead, they build up and occupy more space.
As the bone marrow produces more cancer cells, they begin to overcrowd the blood, preventing the healthy white blood cells from growing and functioning normally.
Eventually, the cancerous cells outnumber healthy cells in the blood.
There is a range of risk factors for leukemia. Some of these risk factors have more significant links to leukemia than others:
Artificial ionizing radiation: This could include having received radiation therapy for a previous cancer, although this is a more significant risk factor for some types than others.
Certain viruses: The human T-lymphotropic virus (HTLV-1) has links to leukemia.
Chemotherapy: People who received chemotherapy treatment for a previous cancer have a higher chance of developing leukemia later in life.
Exposure to benzene: This is a solvent that manufacturers use in some cleaning chemicals and hair dyes.
Some genetic conditions: Children with Down syndrome have a third copy of chromosome 21. This increases their risk of acute myeloid or acute lymphocytic leukemia to 2–3%, which is higher than in children without this syndrome.
Another genetic condition with links to leukemia is Li-Fraumeni syndrome. This causes a change to the TP53 gene.
Family history: Having siblings with leukemia can lead to a low but significant risk of leukemia. If a person has an identical twin with leukemia, they have a 1 in 5 chance of having the cancer themselves.
Inherited problems with the immune system: Certain inherited immune conditions increase the risk of both severe infections and leukemia. These include:
- Bloom syndrome
- Schwachman-Diamond syndrome
- Wiskott-Aldrich syndrome
Immune suppression: Childhood leukemia may develop due to the deliberate suppression of the immune system. This might occur following an organ transplant as a child takes medications to prevent their body from rejecting the organ.
Several risk factors need further studies to confirm their link to leukemia, such as:
- exposure to electromagnetic fields
- exposure to certain chemicals in the workplace, such as gasoline, diesel, and pesticides
- using hair dyes
There are four main categories of leukemia:
Chronic and acute leukemias
During its lifespan, a white blood cell goes through several stages.
In acute leukemia, developing cells multiply quickly and collect in the marrow and blood. They exit the bone marrow too early and are not functional.
Chronic leukemia progresses more slowly. It allows for the production of more mature, useful cells.
Acute leukemia overcrowds the healthy blood cells more quickly than chronic leukemia.
Lymphocytic and myelogenous leukemias
Doctors classify leukemia according to the type of blood cell they affect.
Lymphocytic leukemia occurs if cancerous changes affect the type of bone marrow that makes lymphocytes. A lymphocyte is a white blood cell that plays a role in the immune system.
Myelogenous leukemia happens when the changes affect bone marrow cells that produce blood cells, rather than the blood cells themselves.
Acute lymphocytic leukemia
Children under 5 years old are at the highest risk of developing acute lymphoblastic leukemia (ALL). However, It can also affect adults, typically over the age of 50 years. Out of every five deaths from ALL, four occur in adults.
Chronic lymphocytic leukemia
This is most common among adults over 55 years, but younger adults can also develop it. About 25% of adults with leukemia have chronic lymphocytic leukemia (CLL). It is more common in men than in women and rarely affects children.
Acute myelogenous leukemia
It develops quickly, and symptoms include fever, difficulty breathing, and pain in the joints. Environmental factors can trigger this type.
Chronic myeloid leukemia
Chronic myelogenous leukemia (CML) mostly develops in adults. About 15% of all leukemia cases in the United States are CML. Children rarely develop this type of leukemia.
Treatment options will depend on the type of leukemia a person has, their age, and their overall state of health.
The primary treatment for leukemia is chemotherapy. A cancer care team will tailor this to suit the type of leukemia.
If treatment starts early, the chance of a person achieving remission is higher.
Types of treatment include:
Watchful waiting: A doctor may not actively treat slower growing leukemias, such as chronic lymphocytic leukemia (CLL).
Chemotherapy: A doctor administers medications intravenously (IV), using either a drip or a needle. These target and kill cancer cells. However, they can also damage noncancerous cells and cause severe side effects, including hair loss, weight loss, and nausea.
Chemotherapy is the primary treatment for AML. Sometimes, doctors may recommend a bone marrow transplant.
Targeted therapy: This type of treatment uses tyrosine kinase inhibitors that target cancer cells without affecting other cells, reducing the risk of side effects. Examples include imatinib, dasatinib, and nilotinib.
Many people with CML have a gene mutation that responds to imatinib. One study found that people who received treatment with imatinib had a 5-year survival rate of around 90%.
Interferon therapy: This slows and eventually stops the development and spread of leukemia cells. This drug acts in a similar way to substances that the immune system naturally produces. However, it can cause severe side effects.
Radiation therapy: In people with certain types of leukemia, such as ALL, doctors recommend radiation therapy to destroy bone marrow tissue before a transplant.
Surgery: Surgery often involves removing the spleen, but this depends on the type of leukemia a person has.
Stem cell transplantation: In this procedure, a cancer care team destroys the existing bone marrow with chemotherapy, radiation therapy, or both. Then, they infuse new stem cells into the bone marrow to create noncancerous blood cells.
This procedure can be effective in treating CML. Younger people with leukemia are more likely to undergo a successful transplant than older adults.
Symptoms of leukemia include the following:
Poor blood clotting: This can cause a person to bruise or bleed easily and heal slowly. They may also develop petechiae, which are small red and purple spots on the body. These indicate that blood is not clotting properly.
Petechiae develop when immature white blood cells crowd out platelets, which are crucial for blood clotting.
Frequent infections: The white blood cells are crucial for countering infection. If white blood cells are not working correctly, a person may develop frequent infections. The immune system may attack the body's own cells.
Anemia: As fewer effective red blood cells become available, a person may become anemic. This means that they do not have enough hemoglobin in their blood. Hemoglobin transports iron around the body. A shortage of iron can lead to difficult or labored breathing and pale skin.
Other symptoms may include:
- night sweats
- flu-like symptoms
- weight loss
- bone pain
If the liver or spleen becomes swollen, a person may feel full and eat less, resulting in weight loss.
However, all these can all be symptoms of other illnesses. Consultation and testing are necessary to confirm a diagnosis of leukemia.
A doctor will carry out a physical examination and ask about personal and family medical history. They will check for signs of anemia and feel for an enlarged liver or spleen.
They will also take a blood sample for assessment in the laboratory.
If the doctor suspects leukemia, they may suggest a bone marrow test. A surgeon extracts bone marrow from the center of a bone, usually from the hip, using a long, fine needle.
This can help them identify the presence and type of leukemia.
The outlook for people with leukemia depends on the type.
Progress in medicine means that people can now achieve complete remission through treatment. Remission means that there are no longer signs that cancer is present.
In 1975, the chances of surviving for 5 years or more after receiving a diagnosis of leukemia were 33.4%. By 2011, this figure had risen to 66.8%.
When a person achieves remission, they will still require monitoring and may undergo blood and bone marrow tests. Doctors need to carry out these tests to ensure the cancer has not returned.
The doctor may decide to reduce the frequency of testing if the leukemia does not return over time.