Leukemia, also spelled leukaemia, is a group of cancers that usually begin in the bone marrow and result in high numbers of abnormal white blood cells. These white blood cells are not fully developed and are called blasts or leukemia cells. Symptoms may include bleeding and bruising problems, feeling tired, fever, and an increased risk of infections. These symptoms occur due to a lack of normal blood cells. Diagnosis is typically made by blood tests or bone marrow biopsy.
The exact cause of leukemia is unknown. Different kinds of leukemia are believed to have different causes. Both inherited and environmental (non-inherited) factors are believed to be involved. Risk factors include smoking, ionizing radiation, some chemicals (such as benzene), prior chemotherapy, and Down syndrome. People with a family history of leukemia are also at higher risk. There are four main types of leukemia — acute lymphoblastic leukemia (ALL), acute myeloid leukemia (AML), chronic lymphocytic leukemia (CLL) and chronic myeloid leukemia (CML) — as well as a number of less common types. Leukemias and lymphomas both belong to a broader group of tumors that affect the blood, bone marrow, and lymphoid system, known as tumors of the hematopoietic and lymphoid tissues.
Treatment may involve some combination of chemotherapy, radiation therapy, targeted therapy, and bone marrow transplant, in addition to supportive care and palliative care as needed. Certain types of leukemia may be managed with watchful waiting. The success of treatment depends on the type of leukemia and the age of the person. Outcomes have improved in the developed world. The average five-year survival rate is 57% in the United States. In children under 15, the five-year survival rate is greater than 60 to 85%, depending on the type of leukemia. In children with acute leukemia who are cancer-free after five years, the cancer is unlikely to return.
In 2012, leukemia developed in 352,000 people globally and caused 265,000 deaths. It is the most common type of cancer in children, with three quarters of leukemia cases in children being the acute lymphoblastic type. However, about 90% of all leukemias are diagnosed in adults, with AML and CLL being most common in adults. It occurs more commonly in the developed world.
Scientists don’t understand the exact causes of leukemia. It seems to develop from a combination of genetic and environmental factors.
How leukemia forms
In general, leukemia is thought to occur when some blood cells acquire mutations in their DNA — the instructions inside each cell that guide its action. There may be other changes in the cells that have yet to be fully understood could contribute to leukemia.
Certain abnormalities cause the cell to grow and divide more rapidly and to continue living when normal cells would die. Over time, these abnormal cells can crowd out healthy blood cells in the bone marrow, leading to fewer healthy white blood cells, red blood cells and platelets, causing the signs and symptoms of leukemia.
How leukemia is classified
Doctors classify leukemia based on its speed of progression and the type of cells involved.
The first type of classification is by how fast the leukemia progresses:
- Acute leukemia. In acute leukemia, the abnormal blood cells are immature blood cells (blasts). They can’t carry out their normal functions, and they multiply rapidly, so the disease worsens quickly. Acute leukemia requires aggressive, timely treatment.
- Chronic leukemia. There are many types of chronic leukemias. Some produce too many cells and some cause too few cells to be produced. Chronic leukemia involves more mature blood cells. These blood cells replicate or accumulate more slowly and can function normally for a period of time. Some forms of chronic leukemia initially produce no early symptoms and can go unnoticed or undiagnosed for years.
The second type of classification is by type of white blood cell affected:
- Lymphocytic leukemia. This type of leukemia affects the lymphoid cells (lymphocytes), which form lymphoid or lymphatic tissue. Lymphatic tissue makes up your immune system.
- Myelogenous (my-uh-LOHJ-uh-nus) leukemia. This type of leukemia affects the myeloid cells. Myeloid cells give rise to red blood cells, white blood cells and platelet-producing cells.
Types of leukemia
The major types of leukemia are:
- Acute lymphocytic leukemia (ALL). This is the most common type of leukemia in young children. ALL can also occur in adults.
- Acute myelogenous leukemia (AML). AML is a common type of leukemia. It occurs in children and adults. AML is the most common type of acute leukemia in adults.
- Chronic lymphocytic leukemia (CLL). With CLL, the most common chronic adult leukemia, you may feel well for years without needing treatment.
- Chronic myelogenous leukemia (CML). This type of leukemia mainly affects adults. A person with CML may have few or no symptoms for months or years before entering a phase in which the leukemia cells grow more quickly.
- Other types. Other, rarer types of leukemia exist, including hairy cell leukemia, myelodysplastic syndromes and myeloproliferative disorders.
The causes of leukemia are not known. However, several factors have been identified which may increase your risk. These include:
- a family history of leukemia
- smoking, which increases your risk of developing AML
- genetic disorders such as Down syndrome
- blood disorders, such as myelodysplastic syndrome, which sometimes called “preleukemia”
- previous treatment for cancer with chemotherapy or radiation
- exposure to high levels of radiation
- exposure to chemicals such as benzene
The symptoms of leukemia include:
- excessive sweating, especially at night (called “night sweats”)
- fatigue and weakness that don’t go away with rest
- unintentional weight loss
- bone pain and tenderness
- painless, swollen lymph nodes (especially in the neck and armpits)
- enlargement of the liver or spleen
- red spots on the skin, called petechiae
- bleeding and bruising easily
- fever or chills
- frequent infections
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 headaches, nausea and vomiting, confusion, loss of muscle control, and seizures.
Leukemia can also spread to other parts of your body, including:
- the lungs
- gastrointestinal tract
Leukemia may be suspected if you have certain risk factors, or concerning symptoms. Your doctor will begin with a complete history and physical examination, but leukemia can’t be fully diagnosed by physical exam. Instead, doctors will use blood tests, biopsies, and imaging studies to diagnose you.
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 biopsies can 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.
Once leukemia is diagnosed, it will be staged. Staging helps your doctor determine your prognosis. AML and ALL are staged based on how cancer cells look under the microscope and the type of cell 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 run to assess the progression of the disease, including:
- Flow cytometry examines the DNA of the cancer cells and determines their growth rate.
- Liver function tests show whether leukemia cells are affecting or invading 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 cancer has spread to the central nervous system.
- Imaging studies, such as X-rays, ultrasounds, and CT scans, help doctors look for any damage to other organs that’s caused by the leukemia.
Treatment for your leukemia depends on many factors. Your doctor determines your leukemia treatment options based on your age and overall health, the type of leukemia you have, and whether it has spread to other parts of your body.
Common treatments used to fight leukemia include:
- Chemotherapy. Chemotherapy is the major form of treatment for leukemia. This drug treatment uses chemicals to kill leukemia cells.
Depending on the type of leukemia you have, you may receive a single drug or a combination of drugs. These drugs may come in a pill form, or they may be injected directly into a vein.
- Biological therapy. Biological therapy works by using treatments that help your immune system recognize and attack leukemia cells.
- Targeted therapy. Targeted therapy uses drugs that attack specific vulnerabilities within your cancer cells.
For example, the drug imatinib (Gleevec) stops the action of a protein within the leukemia cells of people with chronic myelogenous leukemia. This can help control the disease.
- Radiation therapy. Radiation therapy uses X-rays or other high-energy beams to damage leukemia cells and stop their growth. During radiation therapy, you lie on a table while a large machine moves around you, directing the radiation to precise points on your body.
You may receive radiation in one specific area of your body where there is a collection of leukemia cells, or you may receive radiation over your whole body. Radiation therapy may be used to prepare for a stem cell transplant.
- Stem cell transplant. A stem cell transplant is a procedure to replace your diseased bone marrow with healthy bone marrow.
Before a stem cell transplant, you receive high doses of chemotherapy or radiation therapy to destroy your diseased bone marrow. Then you receive an infusion of blood-forming stem cells that help to rebuild your bone marrow.
You may receive stem cells from a donor, or in some cases you may be able to use your own stem cells. A stem cell transplant is very similar to a bone marrow transplant.
Some types of leukemia may be prevented by avoiding high doses of radiation, exposure to the chemical benzene, smoking and other tobacco use, or certain types of chemotherapy used to treat other types of cancer.
You can do things at home to help manage your side effects. If your doctor has given you instructions or medicines to treat these symptoms, be sure to follow them. In general, healthy habits such as eating a balanced diet and getting enough sleep and exercise may help control your symptoms.
- Home treatment for nausea or vomiting includes watching for and treating early signs of dehydration, such as a dry mouth or feeling lightheaded when you stand up. Eating smaller meals may help. A little bit of ginger candy or ginger tea can help too.
- Home treatment for diarrhea includes resting your stomach and being alert for signs of dehydration. Check with your doctor before you use any nonprescription medicines for your diarrhea.
- Home treatment for constipation includes gentle exercise along with drinking enough fluids and eating a diet that is high in fruits, vegetables, and fiber. Check with your doctor before you use a laxative for your constipation.
Other problems that can be treated at home include:
- Sleep problems. If you have trouble sleeping, going to bed at a regular time and getting exercise daily are some things that can help.
- Feeling very tired. If you lack energy or become weak easily, try to manage your energy and get extra rest.
- Hair loss. Tips include using a mild shampoo and a soft hairbrush.
- Pain. Home treatment can help you manage pain.
The prognosis of leukemia depends upon the type of leukemia that is present and the age and health status of the patient. Mortality (death) rates for leukemia are higher in the elderly than in younger adults and children. In many cases, leukemia can be managed or cured with treatments available today. In particular, childhood ALL has a very high 5-year survival rate.
Modern treatments have led to a greater than fourfold increase since 1960 in 5-year survival rates for leukemia. For the time period from 2004 to 2010, 5-year survival rates for different types of leukemia were approximately:
AML: 25% overall, 66% for children and teens younger than 15
ALL: 70% overall, 92% for children and teens younger than 15, and 93% for children younger than 5
Chronic myelogenous leukemia (CML) can cause a variety of complications, including:
- Fatigue. If diseased white blood cells crowd out healthy red blood cells, anemia may result. Anemia can make you feel tired and worn down. Treatment for CML also can cause a drop in red blood cells.
- Excess bleeding. Blood cells called platelets help control bleeding by plugging small leaks in blood vessels and helping your blood to clot. A shortage of blood platelets (thrombocytopenia) can result in easy bleeding and bruising, including frequent or severe nosebleeds, bleeding from the gums, or tiny red dots caused by bleeding into the skin (petechiae).
- Pain. CML can cause bone pain or joint pain as the bone marrow expands when excess white blood cells build up.
- Enlarged spleen. Some of the extra blood cells produced when you have CML are stored in the spleen. This can cause the spleen to become swollen or enlarged. The swollen spleen takes up space in your abdomen and makes you feel full even after small meals or causes pain on the left side of your body below your ribs.
- Infection. White blood cells help the body fight off infection. Although people with CML have too many white blood cells, these cells are often diseased and don’t function properly. As a result, they aren’t able to fight infection as well as healthy white cells can. In addition, treatment can cause your white cell count to drop too low (neutropenia), also making you vulnerable to infection.
- Death. If CML can’t be successfully treated, it ultimately is fatal.