Leukemia

Leukemia is a type of cancer that typically begins in the white blood cells. However, leukemia can also begin in the red blood cells or platelets. Leukemia can affect both children and adults.


Anatomy
All blood cells begin as immature cells called stem cells. Within the bone marrow (the soft, fatty tissue inside most bones), stem cells become blasts. The blasts can mature into white blood cells, red blood cells and platelets. White blood cells help your body fight infection, red blood cells deliver oxygen to your tissues, and platelets help blood to clot.

Types of leukemia
Leukemia may be acute or chronic. Acute leukemia evolves quickly, while chronic leukemia usually evolves slowly.
Leukemia is also classified by which type of blood cell it affects:

lymphoid (related to lymphocytes, a type of white blood cell )
myeloid (related to abnormal blood cell development in the bone marrow)
erythroid (related to the red blood cells)
megakaryocytic (related to the platelets)
There are four major types of leukemia:

Acute lymphocytic or lymphoblastic leukemia (ALL) is most common in children. In fact, about half of all childhood leukemias are this type.

Chronic lymphocytic leukemia (CLL) is the most common type of chronic leukemia in adults. A family history of CLL in a first-degree relative, such as a parent or sibling, increases the risk of developing CLL.

Acute myelogenous leukemia (AML) is the most common type of acute leukemia in adults. Exposure to radiation or certain medications or chemicals may increase the risk of developing AML. The risk also increases with age.

Chronic myelogenous leukemia (CML) is usually associated with a specific chromosome abnormality. Exposure to radiation increases the risk of developing CML. The risk also increases with age.
Other rare forms of leukemia include hairy cell, erythroblastic, megakaryocytic and human T-cell leukemia. We'll focus on the most common types of leukemia listed above.


Causes/associate factors
The exact cause of leukemia is unknown. There are certain risk factors, however, such as:
high levels of radiation
exposure to certain chemicals in the workplace, such as benzene and formaldehyde
chemotherapy
certain genetic diseases, such as Down syndrome
smoking
Again, a family history of chronic lymphocytic leukemia in a first-degree relative is also considered a risk factor.


Signs/symptoms
Symptoms of leukemia may include:
fatigue
fever
night sweats
pale skin
bleeding gums, nosebleeds or easy bruising
swollen lymph nodes, liver or spleen
frequent infections
bone pain
weight loss
Because chronic leukemia usually progresses slowly, symptoms may not appear until the disease has been present for quite some time. In fact, chronic leukemia is often identified through a routine blood test, rather than the appearance of specific symptoms.


Diagnosis
Your doctor will ask questions about your medical history and do a physical exam. You'll also need blood tests.
When leukemia is present, a complete blood count often shows anemia (a low number of red blood cells), a low platelet count and an abnormal white blood cell count (either high or low). Other blood abnormalities may be detected as well, depending on the type of leukemia.

A chest X-ray may help the doctor detect any problems with your lungs. Other tests may be done to analyze a sample of cerebrospinal fluid (the fluid that surrounds the brain and spinal cord) and the chromosomes of blood cells, bone marrow or lymph node tissue.

To confirm the diagnosis, a sample of bone marrow may be examined through aspiration or biopsy. With aspiration, a bone marrow sample is removed with a needle attached to a syringe. During a biopsy, a fragment of bone is removed as well. The samples are usually taken from the hip, after the area is numbed with a local anesthetic.


Treatment
During the past 40 years, the five-year survival rate for all types of leukemia has improved from 14 percent to 50 percent. Lymphocytic leukemias have a higher survival rate than myelogenous leukemias. Many acute leukemias can be cured -- up to 80 percent for children who have acute lymphocytic leukemia -- and chronic leukemias can be controlled for longer periods of time than ever before.
Immediate treatment for acute leukemia is essential. Chronic leukemia may or may not require treatment at diagnosis. For any type of leukemia, treatment depends on many factors, such as the type of leukemia, your age, health status and health history, and the presence of symptoms. Treatment options may include:

Chemotherapy
Chemotherapy, or medication to destroy leukemia cells, is often the initial treatment for acute forms of leukemia. Depending on the circumstances, chemotherapy may be done in the hospital, at an outpatient facility, in your doctor's office or in your home.

A single medication or combination of two or more medications may be given through pills or injections into a vein or the cerebrospinal fluid.

Therapy is often given in two or three phases:

The first phase may be a combination of medications given over a period of three to four weeks. The goal of the first phase is to reach remission -- when blood and bone marrow tests return to normal and the leukemia cells are undetectable.

A second phase of treatment is often given to destroy residual leukemia cells.

Then, a maintenance phase of chemotherapy may be recommended for up to two to three years. When no leukemia cells are detected in the blood or bone marrow for a certain period of time, the cancer is considered cured. The definition of cure may depend on the type of leukemia.
New medications that target only leukemia cells but don't hurt normal cells are being developed. One such medication, imatinib mesylate (Gleevec) was recently approved to treat chronic myelogenous leukemia. This special type of targeted therapy is often associated with fewer side effects and less overall risk.

Benefits: Chemotherapy may lead to remission for up to 90 percent of acute leukemias. It may also cure the cancer. Chemotherapy injected into the cerebrospinal fluid can prevent leukemia from spreading to the brain.

Risks: Chemotherapy destroys not only abnormal cells, but healthy cells as well. Specific side effects depend on the particular medication and its dosage. Chemotherapy causes low white blood cell counts (which increases the risk of infection), low red blood cell counts (which may cause fatigue) and low platelets (which increases the risk of bruising and bleeding). The cells in the digestive tract may be damaged, leading to gastrointestinal symptoms such as nausea, vomiting and diarrhea. Sores in the mouth may also develop. Certain chemotherapy medications may cause hair loss. Infertility after treatment is also possible.
Biological therapy
Biological therapy, or immunotherapy, boosts the body's defenses against cancer cells through cytokines (a natural substance that helps fight disease) made in the lab. Biological therapy is usually injected intravenously. Interferon is one type of biological therapy used to treat CML. Monoclonal antibodies are a newer form of biological therapy used to treat CLL and AML. Examples include alemtuzumab (Campath-1H) and rituximab (Rituxan).

Benefits: Biological therapy may lead to remission. Success rates vary depending on the type of leukemia, the specific therapy used and other individual factors.

Risks: Specific side effects depend on the particular therapy. Common side effects include flu-like symptoms, low red blood cell counts (which may cause fatigue), rash and swelling at the injection site.
Radiation therapy
Radiation is occasionally used for certain types of leukemia. This treatment uses high-energy radiation rays to destroy the abnormal cells. It's typically used to target a specific part of the body that has collected a large number of leukemia cells, such as the spleen or brain. Radiation may also be given to the entire body, particularly before a bone marrow transplant.

Benefits: Radiation to the brain and spinal column, done alone or in combination with chemotherapy given through the cerebrospinal fluid, significantly reduces the spread of leukemia to the cerebrospinal fluid and brain.

Risks: Fatigue is a common side effect of radiation. Red, dry skin may also develop. Long-term health problems after radiation may include learning or thinking difficulties, especially for young children after brain radiation.
Bone marrow or stem cell transplantation
A bone marrow or stem cell transplant, in which the leukemia cells are replaced with healthy blood cells, may be done to treat cases of acute leukemia. Transplantation may also be an option when the cancer hasn't responded to traditional treatment or the cancer has relapsed (returned) after treatment with chemotherapy.

Before the transplant, high doses of chemotherapy or radiation are used to destroy the leukemia cells. (Unfortunately, healthy white blood cells are also destroyed during this process.) Then, healthy stem cells (or immature blood cells) are injected intravenously. The stem cells are expected to mature into normal functioning blood cells. If the stem cells are taken from bone marrow, the procedure is called a bone marrow transplant. If the stem cells are taken from blood samples from the patient or a donor, it's called a stem cell transplant.

Benefits: Transplantation can cure some cases of acute leukemia, and it may provide an option when traditional chemotherapy doesn't work. The best outcomes are typically from siblings or other close family members who are good donor matches. Transplantation may help treat chronic myelogenous leukemia in patients younger than 30 when the transplant is done within one year of the diagnosis. Researchers are studying transplantation as a possible treatment for chronic lymphocytic leukemia.

Risks: While the new blood cells are maturing, the body can't fight infection. It can be difficult to get a good bone marrow match. If the tissue of the person receiving the bone marrow reacts to the donated cells, a serious condition known as graft-versus-host disease may develop. Because the risk increases with age, transplantation isn't usually offered to adults older than 55. After transplantation, there's a risk of infections such as pneumonia.

Complications
Various complications are possible.
Leukemia and its treatment may cause low blood cell and platelet counts that require blood transfusions.

Leukemia and chemotherapy both lower immunity, which increases the risk of bacterial and fungal infections.

Chemotherapy can cause nausea, vomiting, diarrhea, mouth sores and possible infertility.

Radiation may cause fatigue, red skin and tissue damage.
Recurrences of leukemia are possible after any type of treatment, so it's important to consult your doctor for regular follow-up visits and let him or her know of any changes in your health status.


Pregnancy-specific information
Pregnancy doesn't increase the risk of developing leukemia. During pregnancy, leukemia increases the risk of slowed fetal growth, premature birth, miscarriage and stillbirth.
Treatment of acute leukemia during the first trimester poses a risk of birth defects, but treatment is considered safe for the baby during the second and third trimesters. For chronic leukemia, conservative therapy during pregnancy may be recommended.


Senior-specific information
Aging increases the risk of developing acute myelogeneous leukemia. Chronic lymphocytic leukemia is most common in adults older than 50, with 65 as the average age of diagnosis.

Prevention
Researchers haven't identified a way to prevent leukemia. However, it's best to avoid possible risk factors, such as smoking.
Limit any potential exposure to benzene, fomaldehyde or other chemicals. If necessary, consult your doctor or employer about ways to do this.

If you've received high levels of radiation as part of the treatment for another medical condition or have other risk factors for leukemia, keep all follow-up visits with your doctor and let him or her know of any changes in your health status.


On the research front
Researchers are studying new biological therapies, medications and combinations of therapies. Clinical trials testing new treatments may be open to those who want to participate voluntarily. For more information, consult your doctor.