(also referred to as acute lymphocytic leukemia and acute lymphoid leukemia)
Acute lymphoblastic leukemia (ALL) is the most common form of childhood cancer. It affects lymphocytes, a class of white blood cells. Leukemic cells accumulate in the bone marrow, replace normal blood cells and spread to the liver, spleen, lymph nodes, central nervous system, kidneys and gonads. About 2,000 children are diagnosed each year in the United States. Peak incidence occurs from ages 3 to 5 years old. The Philadelphia Chromosome Positive aspect of Travis' diagnosis is much more rare and makes finding a potential donor match more difficult, while also making a bone marrow transplant one of the only treatment options as this strain does not respond to conventional therapies which include:
Chemotherapy, treatment with anticancer drugs, is the mainstay of treatment for leukemia. Chemotherapy is considered systemic treatment because the drugs travel through the bloodstream and can kill cells throughout the body. Combinations of two or more anticancer drugs may be given orally or intravenously. Some patients receive drugs intrathecally to destroy cancer cells in the central nervous system. Anticancer drugs are injected directly into the cerebrospinal fluid, which surrounds the brain and the spinal cord. High-dose chemotherapy is treatment with large doses of anticancer drugs in an effort to kill all the leukemic cells.
Radiation therapy, the use of high-energy rays to destroy cancer cells, also may be used to treat leukemia. Radiation therapy is a local treatment because only cells in the treated area are damaged.
* Involved field irradiation is the use of radiation therapy to kill cancer cells in an area of the body where they are known to be present. This area is called the involved field.
* Total-body irradiation may be used before bone marrow transplantation (see below) to kill leukemic cells. In this form of therapy, radiation is generally given in multiple doses over the course of several days to all areas of the body.
Bone marrow transplantation (BMT) is done to allow the administration of very high doses of chemotherapy and, in some cases, to provide the leukemia patient with disease-free bone marrow (see NCI's Research Report: Bone Marrow Transplantation). Marrow for transplantation can be obtained in three ways and is described by its source: another person (allogeneic), an identical twin (syngeneic), or the patient (autologous).
To prepare for BMT, patients receive large doses of drugs and/or radiation in an effort to destroy all leukemic cells. Dosages are so great that the patient's own bone marrow is destroyed, and the patient is totally dependent upon supportive care for control of bleeding and defense against infection.
In allogeneic transplantation, marrow is taken from a matched donor and infused into the patient's bloodstream. The donated cells travel from the blood to the bone marrow where, in time, they usually become functioning marrow.
The success of allogeneic BMT depends partly upon how closely the donor's marrow genetically matches the recipient's marrow. Matching bone marrow involves comparing six characteristic proteins - markers called human leukocyte antigens (HLAs) - on the surface of white blood cells. The more closely the donor's HLAs match the patient's, the greater the chance of successful transplantation. Matching is also important to reduce the chance that the patient's body will reject the donor's marrow. The only perfect HLA match is between identical twins. The next best choice is between close relatives, such as siblings.
Matching also is important to decrease the risk of graft-versus-host disease (GVHD), a major complication of allogeneic BMT. In this disease, the donated marrow reacts against the patient's body. Although mild GVHD may be beneficial in some patients (because the donor's cells can destroy leukemic cells that remain in the body), severe GVHD is potentially fatal. In spite of improved matching techniques, GVHD is not uncommon. Currently, studies are in progress to find techniques that will help prevent GVHD.
Because the patient's own bone marrow is used, autologous bone marrow transplantation eliminates the risk of GVHD. During remission, marrow is removed, frozen, and stored for reinfusion should the patient relapse. To be sure any undetectable leukemic cells that may remain in the patient's marrow are destroyed, the marrow removed from the patient must be treated in a process called purging. Researchers continue to look for more effective methods of purging and better ways to prepare patients for BMT. Therapy using BMT for leukemia patients with advanced, resistant disease has not been successful. Use of BMT earlier in the treatment plan has been more effective.