What is Leukemia?
Leukemia is a group of cancers that develop when the DNA of an immature white blood cell (or less commonly, an immature red blood cell) is damaged in some way. This damage causes the red or white blood cell to grow and divide out of control, and the abnormal cell is then circulated along with healthy blood cells to the rest of the body.
Normal Blood and Bone Marrow
Just like the liver or skin, the bone marrow is an organ. The bone marrow functions to produce blood cells. One part of the bone marrow produces red blood cells and another part produces lymphocytes (white blood cells that are part of the immune system). After they mature, the red blood cells, white blood cells, and platelets formed in the bone marrow are “picked up” by blood that flows through the bone marrow and out to the bloodstream. Blood cells of all types are suspended in plasma to make up the blood that flows throughout the body, and each cell has its own function. Red blood cells bring oxygen to the muscles and organs of the body. Platelets clump together (clot) to slow bleeding from cuts or bruises, and all types of white cells work to fight infections.
Types of Leukemia
Leukemia is divided into four groups according to the type of cell affected and its maturity.
The four main types of leukemia are:
- Acute Lymphocytic Leukemia. Acute lymphocytic leukemia (ALL) is a rapidly progressing leukemia involving lymphocytes, a type of white blood cell.
- Chronic Lymphocytic Leukemia. This type of leukemia also involves the lymphocytes, but progresses much more slowly than ALL.
- Acute Myelogenous Leukemia. Acute myelogenous leukemia (AML) involves myeloid stem cells, and progresses quickly, requiring immediate treatment.
- Chronic Myelogenous Leukemia.This type of leukemia also involves myeloid stem cells, but like CLL, progresses more slowly than the acute forms of leukemia.
Risk Factors for Leukemia
Doctors and researchers are not sure what exactly causes leukemia, but they have identified a few factors that can increase the risk of developing leukemia. Having one or more of these risk factors does not mean that leukemia is inevitable; these are just some common factors that experts have noticed among patients diagnosed with leukemia. These include:
- Exposure to dangerous chemicals such as benzene or formaldehyde. Workers in the chemical industry may be exposed to these chemicals as part of their daily duties, which places them at increased risk for leukemia.
- Exposure to high levels of radiation. Exposure can come from radiation treatment for another cancer, or being near the explosion of a nuclear bomb or the site of a nuclear power plant leak or explosion. Lower levels of radiation, like those used in x-rays have not been shown to increase the risk of developing leukemia.
- Prior chemotherapy. Chemotherapy for other cancers, especially with a type of drug known as an alkylating agent, can increase the risk of developing leukemia.
- Having Downs Syndrome. The presence of this disorder (or less commonly other disorders) involving abnormalities of the chromosomes can increase the risk of leukemia.
- Having myelodysplastic syndrome. Myelodysplastic syndromes (MDS) are a group of diseases in which the bone marrow does not make enough blood cells, or makes blood cells that die quickly once they are in the bloodstream. MDS can be deadly in its own right, even if it does not progress into leukemia. Some consider MDS to be a kind of "pre-leukemia."
Symptoms of Leukemia
According to the National Cancer Institute, people with leukemia may have several symptoms:
- Night sweats and fevers
- Frequent infections
- Weak or tired feelings
- Headaches
- Tendency to bruise or bleed easily
- Abdominal swelling and discomfort
- Lymph-node swelling, particularly in the armpits or the neck
- Unexplained weight loss
While these symptoms might indicate leukemia, they can also point to other conditions, so it's very important to see a doctor if any of these symptoms appear.
Diagnosing Leukemia
Doctors can check for leukemia in different ways, some relatively non-invasive and others a bit more complex. The following tests are used to diagnose leukemia:
- Physical exam to check for abdominal or lymph node swelling or signs of abnormal bruising and bleeding.
- Blood tests to check numbers of white and red blood cells and platelets. High numbers of white cells and low numbers of red cells or platelets is one sign of leukemia.
- Bone Marrow Biopsy. To get a bone marrow sample, the doctor uses a small needle to obtain a marrow sample only (bone marrow aspiration) or a larger needle to get a sample of both bone and marrow (bone marrow biopsy). The bone marrow is then examined and analyzed for abnormal cells.
Treatments for Leukemia
The treatments recommended for each person with leukemia depend on what type of leukemia is present. However, treatment for leukemia can be divided into four main categories:
- Chemotherapy. During chemotherapy, an oncologist prescribes a certain combination of drugs to kill the abnormal leukemia cells. These can be pills or solutions given by injection or through an IV.
- Biological Therapy. This method of fighting leukemia introduces cells such as small molecule inhibitors (the drug Gleevec) or monoclonal antibodies into the immune system to specifically target and kill the leukemia cells.
- Radiation Therapy. Targeted doses of radiation are delivered to the patient under very controlled circumstances.
- Stem Cell Transplantation. Stem cell transplantation can be done in a variety of ways. The most common way is to transplant healthy bone marrow from a donor into the patient but stem cells can also be harvested from umbilical cord blood.
Survival
People used to consider a diagnosis of leukemia a death sentence, but survival rates have improved considerably. With early and appropriate treatment, it is possible to survive for years with leukemia. With this increase in survival comes a new focus on living well with leukemia, rather than planning for the end of life. There is hope, with early treatment and ongoing research into new and better ways to treat and sometimes cure leukemia.
Source:
"What You Need to Know about Leukemia.” National Cancer Institute. September 2002. National Institute of Health. 13 February 2008.
