Introduction
Acute lymphoblastic leukemia (ALL) is a cancer of the bone marrow that arises from immature white blood cells that normally form cells called lymphocytes. Lymphocytes are one of several types of white blood cells. The two subtypes of lymphocytes are known as T and B cells. Approximately 80% of cases of ALL arise from immature B lymphocytes with the remaining 20% arising from T lymphocytes. ALL is more common in children but is also seen in adults, and there is an increased incidence in elderly people.
Cause
The cause of ALL in most cases is unknown. In children, genetic disorders such as Down syndrome can predispose to the development of ALL. Heavy exposure to radiation or toxic chemicals may also predispose to the development of ALL, although in most instances, this has been difficult to prove.
Symptoms and signs
As ALL develops, there is a build-up of abnormal immature white blood cells in the bone marrow and blood. These are known as blast cells (hence the name ‘acute lymphoblastic leukemia’). These abnormal blast cells crowd out the normal cells in the bone marrow and result in a lowering of blood counts. People, therefore, become anemic from low red blood cells and can feel more fatigued and short of breath. Normal white blood cells can decrease in number and cause individuals to be more prone to infection including infections of the sinuses, bronchitis, or pneumonia among others. Cells in the blood, called platelets, that help our blood to clot decrease and sometimes cause bleeding. Because lymphocytes populate our lymph nodes and spleen, some people can have enlargement of lymph nodes in their neck or under their arms or have enlargement of the spleen.
Tests
The most important test is a complete blood count. This will show a low hemoglobin level which causes anemia and an increase or decrease in white blood count depending on how many blast cells are in the blood. Normal white blood cells and platelets will decrease. A bone marrow biopsy is usually done where a needle is inserted in the pelvic bone in the back, and a small portion of bone marrow is extracted for examination under the microscope and for additional genetic testing to look for abnormal genes. These results can help determine the best treatment and the prognosis. Additional blood tests to assess the clotting system and internal organ function are done. Radiologic studies such as computed tomographic (CT) scans are done to assess the lymph nodes and spleen. A needle is inserted in the lower back to sample spinal fluid to look for leukemia cells.
| • | Complete blood count | ||||
| • | Blood clotting function | ||||
| • | Bone marrow biopsy | ||||
| • | Kidney and liver function | ||||
| • | Blood group testing | ||||
| • | Radiologic studies such as CT scan | ||||
| • | Spinal fluid analysis | ||||
Treatment options
Treatment requires the use of multiple chemotherapy drugs to treat the leukemia wherever it is affecting the body. Chemotherapy drugs are administered either by mouth or through a special intravenous line that is placed in a vein in the arm or chest and that can remain in place for many months. The initial goal of chemotherapy is to reduce the number of leukemia cells in the body to a very low level to allow the normal blood cells to grow and put a person in remission. At that point, they should feel better with improvement in their blood counts. Additional treatment known as ‘intensification or consolidation’ is then needed to attack additional leukemia cells that may not be as readily evident with the hope of providing long-term control of the leukemia. Subsequently, maintenance chemotherapy in the form of pills and occasional intravenous injections are given to maintain the remission achieved. Overall, treatment can take up to two to three years to complete.
Drug treatments
The chemotherapy drugs are given in a variety of doses and schedules that have been worked out over many years. Chemotherapy is also given into the spinal fluid to prevent leukemia cells from growing there. The spinal fluid injections occur periodically through the treatment course.
Transfusion of red blood cells and platelets are also frequently required because chemotherapy can lower blood counts.
Radiation treatment
Radiation treatment is sometimes utilized, especially if there is involvement of the spinal fluid. Radiation is needed less frequently than in the past. Radiation is given usually daily on weekdays for several weeks.
Blood or marrow transplantation
In some situations, a blood or marrow transplant (BMT) is recommended and is for situations where it is not felt that chemotherapy alone will be sufficient to control the leukemia. BMT involves the administration of high doses of chemotherapy and/or radiation to the entire body, which severely lowers the blood counts. A new source of stem cells from bone marrow or blood of a donor is administered. These cells, then, are subsequently administered to the patient through a vein to allow their blood counts to recover more quickly and help keep them in remission. BMT also works because the immune system of the donor can help to fight the leukemia.
Outlook
The treatment of ALL has progressively improved over the years. The vast majority of children can now be cured. The chemotherapy regimens used in children are increasingly being applied to young adults, and this has improved their outlook significantly. The treatment of ALL in older adults remains a challenge. Although some adults with ALL can be cured of their leukemia, there exists a continued risk of relapse of the ALL. The use of new forms of BMT in adults has made this approach more available and may contribute to improved outcomes. New treatment types that harness various components of the immune system also appear promising in improving outcomes.
| • | The cause of ALL is unknown. | ||||
| • | Treatment involves the use of multiple chemotherapy agents administered in varying schedules of fluctuating intensity over several years. | ||||
| • | Radiation therapy is sometimes incorporated into the treatment. | ||||
| • | Cure rates for ALL vary based on the subtype of ALL and the patient's age. | ||||
| • | A BMT is sometimes indicated to help improve the outcome. | ||||
Additional resources
There are several online resources available to assist patients in understanding their leukemia and providing financial assistance. In the United States, the Leukemia and Lymphoma Society (http://www.lls.org) provides many helpful resources for patients with ALL as they face their journey through treatment and recovery. For patients who may require a BMT, the Blood and Marrow Transplant Information Network is an excellent resource and advocacy group for BMT patients (http://www.bmtinfonet.org).
Figure 1. Bone marrow sample from a patient with ALL. Large cells with purple nuclei are leukemia cells.
