Childhood acute lymphoblastic leukemia

What is childhood acute lymphoblastic leukemia?

Childhood acute lymphoblastic leukemia (also called acute lymphocytic leukemia or ALL) is a disease in which too many underdeveloped lymphocytes are found in a child's blood and bone marrow. Lymphocytes are infection-fighting white blood cells. ALL is the most common form of leukemia in children, and the most common kind of childhood cancer.

Lymphocytes are made by the bone marrow and by other organs of the lymph system. The bone marrow is the spongy tissue inside the large bones in the body. The bone marrow makes:

• Red blood cells (which carry oxygen and other materials to all tissues of the body)
• White blood cells (which fight infection)
• Platelets (which make the blood clot)

Normally, the bone marrow makes cells called blasts . Blasts develop (mature) into several different types of blood cells that have specific jobs to do in the body.

The lymph system is made up of thin tubes that branch, like blood vessels, into all parts of the body. Lymph vessels carry lymph , a colorless, watery fluid that contains lymphocytes. Along the network of vessels are groups of small, bean-shaped organs called lymph nodes . Clusters of lymph nodes are found in the underarm, pelvis, neck, and abdomen. The spleen (an organ in the upper abdomen that makes lymphocytes and filters old blood cells from the blood), the thymus (a small organ beneath the breastbone), and the tonsils (an organ in the throat) are also part of the lymph system.

Lymphocytes fight infection by making substances called antibodies . Antibodies attack germs and other harmful bacteria in the body. In ALL, the developing lymphocytes become too numerous and do not mature. These immature lymphocytes are then found in the blood and the bone marrow. They also collect in the lymph tissues and make them swell. Lymphocytes may crowd out other blood cells in the blood and bone marrow. If your child's bone marrow cannot make enough red blood cells to carry oxygen, your child may have anemia. If your child's bone marrow cannot make enough platelets to make the blood clot normally, your child may bleed or bruise easily. The cancerous lymphocytes can also invade other organs, the spinal cord, and the brain.

Leukemia can be acute (progressing quickly with many immature cancer cells) or chronic (progressing slowly with more mature-looking leukemia cells). Acute lymphoblastic leukemia progresses quickly, and can occur in both children and adults. Treatment is different for adults than it is for children.

Early symptoms

Early signs of ALL may be similar to those of the flu or other common diseases, such as:

• A fever that won't go away
• Feeling weak or tired all the time
• Aching bones or joints
• Swollen lymph nodes

Diagnosis

If your child has symptoms of leukemia, his or her doctor may order blood tests. These blood tests are used to count the number of each of the different kinds of blood cells. If the results of the blood tests are not normal, a bone marrow biopsy may be performed. During this test, a needle is inserted into a bone in the hip and a small amount of bone marrow is removed and examined under the microscope. This helps the doctor to determine what kind of leukemia your child has and plan the best treatment.

Your child's doctor may also do a spinal tap . A needle is inserted through the back to remove a sample of the fluid that surrounds the brain and spine. The fluid is then examined under a microscope to see if leukemia cells are present.

Your child's chance of recovery (prognosis) depends on:

• Your child's age at diagnosis
• The number of white blood cells in the blood (the white blood cell count) at diagnosis
• How far the disease has spread
• The biologic characteristics of the leukemia cells
• How well the leukemia cells respond to treatment.

Stages of childhood acute lymphoblastic leukemia

There is no staging for childhood acute lymphoblastic leukemia. The treatment depends on age, the results of laboratory tests, and whether or not the patient has been previously treated for leukemia.

Untreated

Untreated acute lymphoblastic leukemia (ALL) means that no treatment has been given except to reduce symptoms. There are too many white blood cells in the blood and bone marrow, and there may be other signs and symptoms of leukemia.

In remission

Remission means that treatment has been given and the number of white blood cells and other blood cells in the blood and bone marrow is normal. There are no signs or symptoms of leukemia.

Recurrent/refractory

Recurrent disease means that the leukemia has come back (recurred) after going into remission. Refractory disease means that the leukemia failed to go into remission following treatment.

Treatment

There are treatments for all patients with childhood acute lymphoblastic leukemia (ALL). The primary treatment for ALL is chemotherapy. Radiation therapy may be used in certain cases. Bone marrow transplantation is being studied in clinical trials.

• Chemotherapy
  Chemotherapy uses drugs to kill cancer cells. Chemotherapy drugs may be taken by mouth, or may be put into the body by a needle in a vein or muscle. Chemotherapy is called a systemic treatment because the drug enters the bloodstream, travels through the body, and can kill cancer cells throughout the body. For ALL, chemotherapy drugs may sometimes be injected (usually through the spine) into the fluid that surrounds the brain and spinal cord. This is known as intrathecal chemotherapy .
• Radiation therapy
  Radiation therapy uses x-rays or other high-energy rays to kill cancer cells and shrink tumors. Radiation for ALL usually comes from a machine outside the body (external beam radiation therapy).
• Bone marrow transplantation
  Bone marrow transplantation is a newer type of treatment. First, high doses of chemotherapy with or without radiation therapy are given to destroy all of the bone marrow in the body. Healthy marrow is then taken from another person (a donor) whose tissue is the same as or almost the same as the patient's. The donor may be a twin (the best match), a brother or sister, or another person not related to the patient. The healthy marrow from the donor is given to the patient through a needle in a vein. The marrow replaces the marrow that was destroyed. A bone marrow transplant using marrow from a relative or person not related to the patient is called an allogeneic bone marrow transplant.
  
  An even newer type of bone marrow transplant, called autologous bone marrow transplant , is being studied in clinical trials. During this procedure, bone marrow is taken from the patient and may be treated with drugs to kill any cancer cells. The marrow is frozen to save it. The patient is then given high-dose chemotherapy with or without radiation therapy to destroy all of the remaining marrow. The frozen marrow that was saved is thawed and given through a needle in a vein to replace the marrow that was destroyed.

Four phases of treatment

There are generally four phases of treatment for ALL.

1. The first phase, remission induction therapy , uses chemotherapy to kill as many of the leukemia cells as possible to cause the cancer to go into remission.
2. The second phase, called central nervous system (CNS) prophylaxis , is preventive therapy. It involves using intrathecal and/or high-dose systemic chemotherapy to the CNS to kill any leukemia cells present there. It is also used to prevent the spread of cancer cells to the brain and spinal cord even if no cancer has been detected there. Radiation therapy to the brain may also be given, in addition to chemotherapy, for this purpose. CNS prophylaxis is often given in conjunction with consolidation/intensification therapy.
3. Once a child goes into remission and there are no signs of leukemia, a third phase of treatment called consolidation or intensification therapy , is given. Consolidation therapy uses high-dose chemotherapy to attempt to kill any remaining leukemia cells.
4. The fourth phase of treatment, called maintenance therapy , uses chemotherapy for several years to maintain the remission.

Treatment by stage

Treatment for childhood acute lymphoblastic leukemia depends on the prognostic group to which your child is assigned. This is based primarily on your child's age and white blood cell count at diagnosis. Your child may receive treatment that is considered standard based on its effectiveness in a number of patients in past studies. Or you may choose to have your child take part in a clinical trial. Not all patients are cured with standard therapy and some standard treatments may have more side effects than are desired. For these reasons, clinical trials are designed to test new treatments and to find better ways to treat cancer patients. Clinical trials are ongoing in most parts of the country for most stages of childhood ALL. For more information, call the Cancer Information Service at 1-800-4-CANCER (1-800-422-6237); TTY at 1-800-332-8615.

Untreated childhood acute lymphoblastic leukemia

Your child's treatment will probably be remission induction chemotherapy to kill cancer cells and cause the leukemia to go into remission. Induction chemotherapy is almost always successful in inducing remission. Intrathecal and/or high-dose systemic chemotherapy, with or without radiation therapy to the brain, may also be given. This helps to prevent the spread of cancer cells to the brain and spinal cord. Clinical trials are testing new ways of inducing remission.

Childhood acute lymphoblastic leukemia in remission

Your child's treatment will probably be intensive chemotherapy to kill any remaining cancer cells. Intrathecal and/or high doses of systemic chemotherapy, with or without radiation therapy to the brain, may also be given during this phase of treatment. This is given to prevent the spread of cancer cells to the brain and spinal cord. Following intensification therapy, chemotherapy generally continues until the child has been in continuous remission for several years.

Recurrent childhood acute lymphoblastic leukemia

Treatment depends on the type of treatment your child received before, how soon the cancer came back following treatment, and whether the leukemia cells are found outside the bone marrow. Your child's treatment will probably be systemic or intrathecal chemotherapy, radiation therapy, or bone marrow transplantation. You may want to consider entering your child into a clinical trial of new chemotherapy drugs or bone marrow transplantation.