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Leukemia is cancer of the blood cells. It begins in the bone marrow when abnormal cells multiply out of control to such an extent that normal blood cells are unable to develop. Leukemia starts in the bone marrow—the soft, spongy material inside bones where blood cells develop from stem cells. Leukemia most often affects the white blood cells, which protect the body against infection. The disease begins when normal development of stem cells into white blood cells goes wrong, creating abnormal white blood cells. Eventually the abnormal white cells overtake other types of blood cells, including red blood cells, which carry oxygen to the body tissues; and platelets, which enable the blood to clot. Leukemia therefore interferes with the blood’s ability to clot and carry oxygen.
The abnormal white cells may also spread to other parts of the body, including the lymph nodes, skin, spleen, liver, brain, and spinal cord.
Leukemia is not one disease but a complex group of diseases. There are four main types of leukemia: acute lymphocytic leukemia (ALL), acute myeloid (or myelogenous) leukemia (AML), chronic lymphocytic leukemia (CLL), and chronic myeloid leukemia (CML).

• Acute lymphocytic leukemia (ALL). ALL develops from white blood cells called lymphocytes. Immature cells that normally grow into lymphoctyes become cancerous and build up rapidly in the bone marrow, replacing normal stem cells. The blood transports these abnormal cells to the lymph nodes, spleen, liver, kidneys, and other organs. These cells can cause meningitis, kidney and liver failure, anemia, and other conditions.
• Acute myeloid leukemia (AML). AML develops from cells in the bone marrow that normally grow into specific white blood cells called granulocytes. Instead of developing normally, the cells become cancerous and multiply rapidly in the bone marrow. These abnormal cells may grow under the skin, forming small tumors, and result in anemia, meningitis, and damage to the liver, kidneys, and other organs.
• Chronic lymphocytic leukemia (CLL). In CLL, mature lymphocytes become cancerous and begin to multiply, starting in the lymph nodes. The abnormal cells spread to the bone marrow, and then the spleen and liver, which become enlarged. The shortage of normal blood cells and an abnormal reaction by the immune system causes anemia. The immune system attacks normal tissues, destroys normal red blood cells and platelets, and causes joint inflammation and thyroid gland inflammation (thyroiditis). Subtypes of CLL are named according to the type of lymphocyte affected. The most common type of CLL is B-cell leukemia. Less common are T-cell leukemia, Sézary syndrome, and hairy cell leukemia, in which the abnormal cells have hair-like projections when viewed under a microscope.
• Chronic myeloid leukemia (CML). In CML, bone marrow cells become cancerous and produce large amounts of abnormal granulocytes that may be either immature or mature. These abnormal cells crowd out the normal bone marrow cells. As larger numbers of immature granulocytes enter the bloodstream and bone marrow, the number of red blood cells and platelets decreases. Most often, CML progresses to a stage called blast crisis, in which the bone marrow produces only immature granulocytes. This is a sign that the disease has worsened.

Causes

The cause of leukemia is unknown. At present, no one knows what causes leukemia. However, scientists have discovered some risk factors that increase a person’s chance of getting the disease. These may include excess exposure to radiation, or prior treatment for a malignancy, or having had a previous blood disorder. However, most people who develop leukemia do not have any of these risk factors.
CLL is rare in China and Japan, and remains rare among Japanese people who move to the U.S. This suggests that genetic factors play some role in the development of CLL.
Symptoms

The symptoms of leukemia, such as frequent infections and easy bruising and bleeding, result from the blood cells’ inability to perform their normal functions. However, at the time of diagnosis of either CLL or CML, patients may have no symptoms. People with leukemia get infections because their white blood cells do not protect them from disease. They become anemic because of a shortage of healthy red blood cells. They bleed and bruise easily because they lack enough platelets to enable their blood to clot.
Other symptoms depend on which parts of the body the leukemia cells invade. In acute leukemia, cells often collect in the brain and spinal cord, causing headaches, confusion, vomiting, loss of muscle control, and seizures. Some people develop sores on the skin or in the eyes. In both chronic and acute leukemia, various organs may be affected, including the skin, central nervous system, digestive tract, testicles, and kidneys.
Common symptoms of leukemia include:

• fever, chills, and other flu-like symptoms
• fatigue and weakness
• frequent infections
• loss of appetite and/or weight
• swollen or tender lymph nodes, liver, or spleen
• easy bruising or bleeding
• swollen or bleeding gums
• small red spots under the skin
• sweating, especially at night
• bone or joint pain

In acute leukemia, symptoms appear suddenly and worsen rapidly. Symptoms of acute leukemia include:

• severe infection
• paleness (a sign of anemia)
• feeling weak and short of breath
• nosebleeds
• easy bruising
• purple blotches on the skin
• headaches
• irritability
• vomiting
• joint and bone pain
• swollen glands
• swollen, painful, bleeding gums.

The symptoms of chronic leukemia may take a long time to develop, and may be quite mild at first. Frequently the doctor finds chronic leukemia when you have a blood test during a routine checkup. About a fifth of the people who get chronic leukemia have no symptoms when their cancer is found by a blood test. Often the first symptoms are very general, such as enlarged lymph nodes. You may also lose your appetite, lose weight, feel tired, become short of breath when you exercise, and have a sense of fullness in your abdomen, which is caused by an enlarged spleen.
As the disease develops, you may grow pale and start to bruise easily. Chronic leukemia usually does not lead to infections until the later stages of the disease. Because CLL progresses slowly, you may not need treatment for years. Treatment is not given until you develop symptoms, or until it is clear that the disease is progressing. In the later stages of CML, you may develop fever, enlargement of the lymph nodes, and lumps under the skin.
Risk Factors

In general, more adults than children get leukemia. Children usually get acute leukemia (particularly ALL), while adults are more likely to have chronic leukemia. The American Cancer Society estimates that every year about 28,800 adults and 2,600 children in the US get leukemia. Most people with chronic leukemia are adults; only about 2% of cases of chronic leukemia occur in children.

• ALL is the most common cancer in children. Most children who get it are between the ages of 3 and 5, but it can also affect adolescents, and sometimes adults.
• AML affects mostly adults, but still causes nearly half of the cases of leukemia among children.
• CLL affects only adults, most of whom are over the age of 60. Men are two to three times more likely to get this form of leukemia than women.
• CML affects mostly adults. Children get it only rarely.

Several other factors can increase your risk of getting leukemia.

• Smoking is a known risk factor for leukemia. Cancer-causing substances in tobacco smoke can travel through the bloodstream and affect other parts of the body, as well as the lungs.
• High-voltage power lines. Some research suggests that exposure to electromagnetic fields from high-voltage power lines may be a risk factor for leukemia.
• High-dose radiation. Exposure to high-dose radiation, as from a nuclear reactor accident or from therapeutic radiation, increases the risk for most types of leukemia.
• Chemicals. Workers exposed to benzene and farm workers exposed to pesticides or herbicides over long periods of time are at greater risk for developing leukemia.
• Genetic conditions. Certain genetic conditions can increase the risk for leukemia. For example, children with Down syndrome are more likely to get the disease.
• Chemotherapy. Being treated with certain chemotherapy drugs for other types of cancer increases the risk for AML.
• A virus known as HTLV-1, which is similar to the virus that causes AIDS, increases a person’s risk for T-cell leukemia.
• Family history. Having a first-degree relative (parent or sibling) who has had CLL increases a person’s chance for getting CLL.

Diagnosis

To diagnose leukemia, the doctor will first perform a physical exam. Your doctor will ask about your medical history; particularly whether you have any of the general symptoms listed above. In the physical examination, the doctor will feel for swelling of the liver, the spleen, and the lymph nodes in the groin, neck, and underarms. You will also be examined for abnormal bleeding.
The doctor will then order laboratory and other tests to detect whether you have leukemia, and find out what type it is. Depending on whether you have acute or chronic leukemia, your doctor may conduct one or several tests.

• Complete blood count (CBC). For this test, a blood sample is examined under the microscope to see how the cells look and to count the numbers of different types of cells. In acute leukemia, there will usually be too many white cells, and most of them will be immature. There will also be too few red cells and platelets. In chronic leukemia, there are also too many white blood cells (although many are mature), and too few red blood cells and platelets.
• Bone marrow tests. To confirm the diagnosis and to learn what type of leukemia you may have, a sample of bone marrow is examined under a microscope. Bone marrow is obtained either by bone marrow aspiration or biopsy. In a bone marrow aspiration, a doctor inserts a thin needle into a large bone (usually the hip) and draws out a sample of liquid bone marrow. A bone marrow biopsy is done with a larger needle, and extracts a sample of bone as well as bone marrow.
• Spinal tap. In this test, also called lumbar puncture, the doctor inserts a needle into the space around the spinal cord to draw out fluid, which is then examined to see if it contains leukemia cells. This procedure is done only if a diagnosis of leukemia is made, and is performed to determine if the leukemia cells have spread to other parts of the body.
• Lymph node biopsy. In a few cases, it may be necessary to remove an entire lymph node to test for leukemia cells.
• Cytogenetics (chromosome analysis). This test analyzes the shape and number of the chromosomes in the leukemia cells. It can identify chromosome alterations typical of specific types of leukemia.
• Immunophenotyping. This method uses antibodies that react with substances called antigens on cell membranes. It can distinguish normal cells from leukemic cells, or lymphocytic from myelogenous leukemia cells. It can also identify cell subtypes, which helps your physician decide on the best treatment.
• Imaging studies. Your doctor may use various methods of creating pictures of the inside of the body to find masses of leukemia cells in different organs.
  • X-rays can reveal a mass in the chest.
  • Ultrasound, which uses sound waves, shows whether the kidneys, liver, or spleen have been invaded by leukemia cells.
  • Gallium scan or bone scan. For these tests, the doctor injects a radioactive chemical that collects in an area where there is cancer or infection. The location of this area then shows up on an x-ray. These tests can reveal whether bone pain is caused by cancer or infection.

Prevention and Screening

Since the cause of leukemia is unknown, there is no way to prevent it. You can, however, reduce your risk by not smoking and avoiding exposure to chemicals known to cause leukemia. Since smoking is a known risk factor for AML, avoiding or quitting smoking can reduce your risk for getting that type of leukemia. Avoiding excess exposure to benzene and other cancer-causing chemicals is also advisable.
Treatment

Self-Care
Know what questions to ask your doctor so that you can play an active role in your treatment. The shock of a diagnosis may make it hard to remember all the questions you want to ask, or to remember everything the doctor says. It's helpful to write down all your questions in advance, and to take notes or tape record the doctor’s answers, or to bring someone with you. Some questions you may want to ask include:

• What kind of leukemia do I have?
• What are my treatment choices? Which do you recommend? Why?
• What are the benefits of each treatment?
• What are the risks and possible side effects of each treatment?
• Is there anything I can do to decrease any side effects?
• If I have pain, how can you relieve it?
• How long will the treatment last?
• Will I have to change my everyday activities?
• How much will the treatment cost? How do I find out whether my insurance will cover it?
• What is the risk of the leukemia returning if I am in remission?
• Can I be cured of this leukemia?

It may be helpful to get a second opinion about your diagnosis or treatment plan. Your own doctor may be able to refer you to another hematologist or a cancer specialist. You can also get names from your local medical society, a hospital, or a medical school. Call the National Cancer Institute’s Cancer Information Service (1-800-4-CANCER) for information about cancer centers and other treatment centers in your area.
Minimize your risk of infection. Washing your hands thoroughly and not eating raw vegetables and fruits will help you to avoid infection. While you are receiving treatment for leukemia, you should avoid people who are sick and stay away from crowds. However, this is not necessary for people with stable-phase CML.
Drug Therapy

Your doctor is the best source of information on the drug treatment choices available to you.
Other Therapies

Some leukemia patients may have radiation therapy in addition to chemotherapy.
Radiation therapy uses high-energy x-rays to shrink tumors and stop cancer cells from growing.
Most often it targets a specific area of the body, such as an enlarged spleen. Radiation can also relieve bone pain caused by growth of leukemia cells in the bone marrow. For people with acute leukemia, radiation could be used on collections of leukemia cells in the testicles or central nervous system. Some patients might have radiation over their entire body before a bone marrow transplant.
If you receive radiation you may experience a number of side effects, including tiredness, hair loss, red, dry, tender, and itchy skin, nausea and vomiting, and loss of appetite. These effects are temporary.
Bone marrow transplantation (also called stem cell transplantation) replaces diseased stem cells with healthy ones to restore the bone marrow’s ability to produce blood cells. In bone marrow transplantation, diseased bone marrow is destroyed by high doses of radiation and chemotherapy. It is then replaced by healthy bone marrow cells. The healthy cells may be taken from the patient's own marrow before the procedure, treated to remove the diseased cells, and stored. The healthy cells may also come from a donor. Most often donor marrow is used, since most people with leukemia do not have enough cancer-free cells in their bone marrow. The donor usually must be a close relative with a matching tissue type. For a patient without an appropriate family donor, searches for a matched donor can be done through registries.
The healthy cells are delivered via blood transfusion, after which they begin growing in the bone marrow and producing normal blood cells. This may take three weeks or longer. During this time, you must stay in the hospital where you are protected from germs until you have enough white blood cells to fight infection. If you have received stem cells from a donor, you will be given drugs to prevent your body from rejecting the cells or from attacking your own body. You will also be given drugs to prevent infection.
Bone marrow transplantation may help people with acute leukemia who have not responded to chemotherapy, or whose disease has come back after a remission. For people with CML, this procedure has been the only hope for cure. For chronic leukemia, bone marrow transplantation can provide a good remission. There are, however, side effects of bone marrow transplantation:

• Increased risk of infection, hair loss, nausea, and vomiting from the radiation and chemotherapy
• Graft-versus-host disease. This is a serious post-transplant reaction in which the donor (graft) cells reject the host (body) cells into which they were implanted. This condition may occur right away, or not for years. You will receive drugs to prevent this.
• Damage to your lungs from radiation, resulting in shortness of breath. Specifically, the damage is due to pneumonia, which may be permanent and/or lethal.
• Infertility for women caused by damage to the ovaries.
• Damage to the thyroid gland, leading to problems with metabolism.
• Cataracts caused by damage to the lens in your eye.

Infusion of donor lymphocytes is a new technique that shows promise. Infusing lymphocytes (as opposed to stem cells) from a donor has led to remission for patients with CML who had a relapse after bone marrow transplantation. Scientists are currently studying this procedure to see if it will work for other conditions.
Medications and other supportive care is important to relieve or prevent many side effects and complications caused by leukemia and its treatment. Your doctor will use a variety of measures to manage the symptoms of leukemia and the side effects of your treatment.

• Anti-emetics. Drugs you take while receiving chemotherapy can prevent or decrease nausea and vomiting.
• Growth factors. Drugs called growth factors can raise your blood count and lower your risk of infection.
• Anti-toxins. When leukemia cells are destroyed, they release toxins that travel through the body in the bloodstream and can damage the heart, kidneys, and nervous system. To prevent this damage, you may be given drugs and extra fluids that flush these toxins from the body.
• Red blood cell transfusion. If you are tired or short of breath due to low levels of red blood cells, you may be given a transfusion of these cells.
• Platelet transfusion. If your platelet count is low, you may receive a platelet transfusion to decrease the risk of uncontrolled bleeding.
• Mouth sensitivity, bleeding, and risk for infection. Leukemia can cause sensitivity and bleeding in your mouth, as well as a greater risk of mouth infection. Your doctor may tell you to have a dental exam before you start treatment. Your dentist can tell you how to keep your mouth healthy and clean during your treatment.

Clinical trials are research studies that test new treatments on people after these treatments have been studied in the lab. Many leukemia patients take part in clinical trials, which give them access to promising new drugs and other treatments. Ask your doctor if there is a clinical trial that might benefit you. Clinical trials involve risks as well as benefits, and it is important to understand what these are. Call the National Cancer Institute at 1-800-4-CANCER for more information about clinical trials.
Surgery

The only operation used in treating leukemia is removal of the spleen. Since leukemia affects the blood and bone marrow, there is no solid tumor to cut out to cure the disease. Surgery, however, may still be used to increase your comfort. If the spleen is affected by leukemia, it may become so large that it presses on other organs and causes discomfort. In that case an operation to remove the spleen will bring relief, though it will not cure the leukemia.
A surgical procedure may be used to insert a tube into a large vein. This allows chemotherapy or other drugs to be given without repeated injections with a needle.
Alternative Medicine

Alternative therapies may help you by relieving the side effects of leukemia treatments or by boosting your immune system. Some alternative therapies have been well-studied, so their effects are scientifically proven. Others have not undergone study, and their effects are unproven. Consult your physician before embarking on alternative therapies.
Special Circumstances

Most children who get leukemia have the acute type. The treatment they receive depends on whether they are at high risk or low risk. Children with leukemia are put into either a high-risk or low-risk group based on their white blood cell count (lower is better), features of their chromosomes, and their response to treatment (an early response means the child will do better). Those at high risk receive more intensive treatment.
Children may suffer long-term side effects from radiation and chemotherapy. Some of these long-term side effects may include:

• Difficulty with learning and coordination. This can occur in children who have had radiation to the brain, and can result in poor school performance. For this reason, children receive radiation only when chemotherapy fails to work or in patients with high-risk acute lymphoblastic leukemia.
• Infertility. Boys who receive radiation to their testicles usually cannot have children when they grow up. The radiation may also decrease hormone production, so they need to take hormones later on.
• Heart damage. Both drugs (particularly anthracyclines and radiation) can cause damage to the heart such that it cannot pump adequately.
• Risk of AML. A small number of children who are given certain chemotherapy drugs for ALL—particularly alkylating agents—develop AML. This risk must be weighed against the benefit of using chemotherapy to treat ALL.

Prognosis

Many cases of acute leukemia can be cured; however, chronic leukemia can only rarely be cured. Your prognosis will depend on the particular type of leukemia you have and on the particular features of your case. If you have gone five years after treatment without any signs of disease (two years for children), the chance that your leukemia will recur is small.

• ALL. In over 90% of cases, the first course of chemotherapy brings about a remission. Fifty percent of children who have ALL are free of disease five years after their treatment. Young children between the ages of three and seven have the best prognosis, while the outlook for people over 20 is less favorable. Both children and adults whose first white blood cell counts are under 25,000 per microliter of blood have a better prognosis than people whose counts are higher.
• AML. For 50% to 85% of people with AML, treatment brings about a remission. Between 20% and 40% of people with this disease remain disease-free after 5 years. People who get AML after having radiation and chemotherapy for another disease, as well as those over 50, have the poorest prognosis.
• CLL. For those with CLL, the chances for recovery depend on how advanced their disease is. This is indicated by the numbers of lymphocytes and platelets, whether they have anemia, and whether they have an enlarged spleen or lymph nodes. People who have B-cell leukemia, the most common type of CLL, may live 10 to 20 years after the disease is diagnosed. Severe anemia and a low platelet count are signs of a worse prognosis. Another factor is that having CLL increases the chance that you will develop another form of cancer.
• CML. A bone marrow transplant during the early stages of CML offers a chance for cure. However, 20% to 30% of people with this disease die within 2 years after receiving a diagnosis. Another 25% die in each following year. Others may survive another 4 years or more until blast crisis occurs. Most often patients die within 2 months of a blast crisis, but some live another 8 to 12 months with chemotherapy. Interferon-alpha and Gleevec have led to remission in some patients, so there is hope that new treatments will improve the outlook for people with CML.

Follow-up

For several years after your treatment ends, you will need to see your doctor often for follow-up visits. Follow-up exams are extremely important. They enable your doctor to check for signs that your leukemia has recurred, and to watch for the appearance of any long-term side effects of treatment. It is essential that you tell your doctor if you experience any new symptoms.