What is acute lymphocytic leukemia (ALL)?

Related conditions:
Acute myeloid leukemia, chronic lymphocytic leukemia, chronic myeloid leukemia

Definition:


Acute lymphocytic leukemia (ALL) is a cancer of the white blood cells. A lymphocyte is a type of white blood cell made in the bone marrow that helps fight infection. In this fast-growing type of cancer, for unknown reasons, the bone marrow begins to make lymphocytes that develop abnormally. “Acute” means that the disease affects lymphocytes before they are fully formed and that it progresses rapidly if not treated.

Risk factors: Few risk factors exist for ALL. Receiving high doses of radiation, usually as treatment for another type of cancer, is one risk factor. Exposure to benzene may also be a factor. Risk increases in people with certain other diseases, such as Down syndrome, Fanconi anemia, Bloom syndrome, and some other genetic diseases. In about 25 percent of ALL cases, the patient has a chromosome mutation in which parts of chromosome 9 and chromosome 22 have changed places. Having a sibling, especially a twin, with ALL also increases the risk for this disease. Researchers are exploring lifestyle or environmental relationships, but it appears that many factors, including a combination of genetic and environmental factors, may be involved in developing ALL.

Etiology and the disease process: Through a genetic process that is not completely understood, cells in bone marrow begin to form abnormally. ALL can begin in two different types of lymphocytes, either B cells or T cells. As the abnormal lymphocytes quickly grow, they crowd out the red and white blood cells and platelets that the body needs and that are also created in the bone marrow. The symptoms of ALL come from the crowding out of these normal, healthy cells. These cells may then spread into the lining of the spine and brain.

Incidence: The American Cancer Society estimates that about 6,020 people in the United States were diagnosed with ALL in 2014. It is slightly more common in men than in women, and slightly more common in white children than in children of other races. ALL occurs in people of all ages but has a peak incidence in children between the ages of two and five. After age five, risk decreases, then increases again in people over age fifty. It is the most common type of leukemia in children under the age of fifteen, accounting for about 75 to 80 percent of childhood leukemias, according to the Dana-Farber Cancer Institute. It occurs more often in developed countries and in people with higher socioeconomic status.

Symptoms: Symptoms of ALL include anemia, body aches, bone pain, bruises without any injury, enlarged lymph nodes, an enlarged spleen, excessive bleeding from minor injuries, fever with no illness or lasting low-grade fever, frequent infections, headaches, joint pain, nosebleeds, paleness, shortness of breath during activity, tiredness, vomiting, and unexplained weight loss.

Screening and diagnosis: There is no screening test for ALL. Blood and bone marrow tests are necessary to diagnose ALL. These tests look for abnormal lymphocyte cells. A bone marrow aspirate test and a bone marrow biopsy are two possible tests. The bone marrow aspirate test looks for abnormal cells in the bone marrow and can also be used for other types of analysis. A bone marrow biopsy can show how much disease is already in the bone marrow. The results of these tests help determine which type of drug therapy to use and how long treatment should last.

If a patient has been diagnosed with ALL, a lumbar puncture may be performed to see if the abnormal cells have moved into the fluid surrounding the spine and brain. Chest X rays, ultrasounds, or additional blood tests may also be used to determine the spread of the disease.

Depending on where the cancer started and the results of testing, ALL may be categorized into early pre-B-cell ALL, common ALL, pre-B-cell ALL, mature B-cell ALL, pre-T-cell ALL, or mature T-cell ALL. The type of ALL helps determine which therapy to use and how long treatment should last. According to the American Cancer Society, about 85 percent of ALL cases begin in B cells, and these cases are generally classified as lower risk.

ALL may also be classified or staged using the French-American-British (FAB) classification system. In this older system, ALL is classified according to the type of abnormal cells as follows:

• ALL-L1: small, uniform abnormal cells





• ALL-L2: large, varied abnormal cells





• ALL-L3: large, varied, bubble-like cells

This system, however, has largely been replaced, as newer tests allow for more accurate classification.

Treatment and therapy: Patients diagnosed with ALL should start treatment immediately. The course and length of treatment chosen depend on the results of the patient’s bone marrow tests, the patient’s age, the number of ALL cells in the blood, whether certain chromosomal changes have already happened, whether ALL cells began in the B cells or the T cells, and whether ALL has spread to the brain covering or spinal cord. During therapy, bone marrow tests may be done again to make sure the treatment is destroying the cancer cells.

The first part of treatment for ALL is called induction therapy. This therapy helps kill ALL cells and get a patient’s blood counts back to normal (remission). Some of the drugs used in induction therapy are given by mouth. Others are given in a vein, usually through the patient’s chest. Most often, this chemotherapy for ALL involves combining drugs to improve the effects of the drugs. Often, ALL spreads into the lining of the spinal cord and the brain. To kill these ALL cells, drugs are injected directly into the spinal fluid. Radiation therapy may be used on the spine and brain either with or without the injected drugs.

Post-induction therapy, the second part of treatment for ALL, begins when a patient has reached remission. This type of therapy is needed because usually some ALL cells that cannot be detected by tests remain in the body. Post-induction therapy usually happens in two- or three-year cycles. The drugs used in post-induction therapy are usually different from those used in induction therapy, and the type of drugs used depends on how the patient responded to induction therapy and whether the patient has certain chromosome abnormalities. A patient may also need maintenance therapy after post-induction therapy to prevent the cells from regrowing.

T-cell ALL, infant ALL, and adult ALL are all forms of high-risk ALL. These types of ALL are usually treated with higher doses of drugs during both induction and post-induction therapy. Some patients with high-risk types of ALL may respond well to bone marrow or cord blood transplant therapy.

A bone marrow or cord blood transplant may be used when high doses of drugs are given to kill the ALL cells. These high doses of drugs may also kill healthy cells in the bone marrow. This transplant gives a patient healthy cells to replace the killed bone marrow cells. A transplant is a high-risk procedure and will probably not be used unless a patient does not have a good possibility of long-term remission with chemotherapy. High-risk ALL patients are more likely to have a transplant. The timing of a transplant is important; a patient has a better chance of a successful transplant when he or she is in remission at the time of transplant.

Prognosis, prevention, and outcomes: There is no known way to prevent ALL. Most children with ALL can be cured of this disease with proper treatment. In 2012, the American Cancer Society announced that children diagnosed with ALL between 2000 and 2005 had a five year survival rate of 90.4 percent, up from 83.7 percent for those diagnosed between 1990 and 1994.

Most adults also improve with treatment; the number of adults who have remissions has increased, and the length of adult remissions has improved. The overall survival rate for adults after chemotherapy is about 40 percent, according to the American Cancer Society, and adults with low-risk ALL have even higher survival rates.

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