Leukemia Adult Acute
Acute Lymphocytic Leukemia
Acute lymphocytic leukemia (ALL), also called acute lymphoblastic leukemia, is a type of cancer that starts from white blood cells in the bone marrow (the soft inner part of the bones) called lymphocytes. In most cases, ALL quickly moves into the blood. It can then spread to other parts of the body including the lymph nodes, liver, spleen, central nervous system (brain and spinal cord), and testes.
Other types of cancer that start in these organs and then spread (metastasize) to the bone marrow are not leukemia. In ALL, this difference is very important because the patient may have a lymphoma, a cancer of lymphocytes that generally begins in lymph nodes. Sometimes it is difficult to tell whether a patient with malignant lymphocytes in lymph nodes and bone marrow has leukemia or lymphoma. One rule of thumb is, if more than 25% of the bone marrow is replaced by malignant lymphocytes, it is called leukemia. Another depends on the size of lymph nodes. The bigger they are, the more likely the disease is a lymphoma.
Acute means that the leukemia develops quickly, and if not treated, would probably be fatal in a few months. Lymphocytic or lymphoblastic means it develops from cells called lymphocytes or lymphoblasts. It is different from acute myeloid leukemia that develops in a different white blood cell type found in the bone marrow. For more information on this leukemia see the ACS document, Acute Myeloid Leukemia.
What Causes Acute Lymphocytic Leukemia?
Although some people with acute lymphocytic leukemia have one or more known risk factors mentioned earlier, most do not. The cause of their cancer remains unknown at this time. Even when a patient has one or more risk factors, there is no way to tell whether it actually caused the cancer. And many people with one or more cancer risk factors never develop this disease.
The development of normal human cells mostly depends on the information contained in the cells’ chromosomes. Chromosomes are large molecules of DNA. DNA is the chemical that carries the instructions for nearly everything our cells do. We usually resemble our parents because they are the source of our DNA. However, DNA affects more than the way we look. During the past few years, scientists have made great progress in understanding how certain changes in DNA can cause normal bone marrow cells to become leukemic cells. DNA is the chemical that carries the instructions for nearly everything our cells do. We usually resemble our parents because they are the source of our DNA. However, DNA affects more than the way we look..
Some genes (parts of our DNA) contain instructions for controlling when our cells grow and divide. Certain genes that promote cell division are called protooncogenes. Others that slow down cell division or cause cells to die at the appropriate time are called tumor suppressor genes. We know that cancers can be caused by DNA mutations (gene defects) that turn on protooncogenes or turn off tumor suppressor genes. Every time a cell prepares to divide into two new cells, it must duplicate its DNA. This process is not perfect and copying errors can occur. Fortunately, cells have repair enzymes that proofread DNA. But some errors may slip past, especially if the cells are growing rapidly.
What Are the Risk Factors for Acute Lymphocytic Leukemia?
A risk factor is anything that increases a person's chance of getting a disease such as cancer. Risk factors are lifestyle-related, environmental, or genetic (inherited).
Lifestyle-related risk factors for some types of cancer include such things as smoking or unprotected exposure to strong sunlight. At this time there are no known lifestyle-related risk factors for acute lymphocytic leukemia.
Environmental risk factors are influences in our surroundings such as radiation, chemicals, and infections. Only radiation exposure (such as being a survivor of an atomic bomb blast or nuclear reactor accident) has been linked to ALL.
There is conflicting evidence about electromagnetic field (EMF) exposure (such as that occurring near very high-voltage power lines) as a potential risk factor for developing leukemia. The United States National Cancer Institute has several large studies going on now to look into this question. Most studies published so far suggest either no increased risk or a very slightly increased risk. Clearly, most cases of leukemia are not related to EMF exposure. Infection with the human T-cell lymphoma/leukemia virus (HTLV-1) can cause a rare type of acute lymphocytic leukemia.
Most cases occur in Japan and the Caribbean area, and this disease is not common in the United States. Burkitt lymphoma, a disease more common in Africa, can form a type of acute lymphocytic leukemia. It has been linked to infection with the Epstein-Barr (EB) virus (the virus that causes infectious mononucleosis, or "mono"). Acute lymphocytic leukemia does not appear to be an inherited disease, although some syndromes with a genetic basis, such as Down syndrome, seem to raise the risk. ALL is more common in whites than in African Americans, and is slightly more common in males than in females, although the reasons for this are not clear.
How Is Acute Lymphocytic Leukemia Treated?
Adult acute lymphocytic leukemia (ALL) is not a single disease. It is really a group of related diseases, and it is important to remember that patients with different subtypes of ALL vary in their prognosis and response to treatment. Treatment options for each patient are based on the FAB subtype of the leukemia as well as certain prognostic features (described in the previous section). Several different types of treatment may be used in people with acute lymphocytic leukemia. The major therapy is chemotherapy. Surgery and radiation therapy may be used in special circumstances.
Credit: National Institute of Health.