What Is Acute Lymphocytic Leukemia?
Acute lymphocytic
leukemia (ALL) is a type of cancer in which the bone marrow makes too many lymphocytes, which is a type of white blood cell. Acute lymphocytic leukemia, which is also called acute lymphoblastic leukemia, accounts for about 3,800 new cases of leukemia each year. Although acute lymphocytic leukemia is the most common type of leukemia in young children, it can also affect adults.
Understanding Blood Cells
Normally, the body produces bone marrow stem cells (immature cells) that develop into mature blood cells.
The three types of mature blood cells include:
- Red blood cells that carry oxygen and other materials to all tissues of the body
- White blood cells that fight infection and disease
- Platelets that help prevent bleeding by causing blood clots to form.
In acute lymphocytic leukemia, too many stem cells develop into a type of white blood cell called lymphocytes. These lymphocytes may also be called lymphoblasts or
leukemia cells.
The three types of lymphocytes include:
- B lymphocytes that make antibodies to help fight infection
- T lymphocytes that help B lymphocytes make the antibodies that help fight infection
- Natural killer cells that attack cancer cells and viruses.
In acute lymphocytic leukemia:
- The lymphocytes are not able to fight infection very well
- The number of lymphocytes increases in the blood and bone marrow
- There is less room for healthy white blood cells, red blood cells, and platelets.
This may cause infection, anemia, and easy bleeding. Acute lymphocytic leukemia can also spread to the central nervous system (brain and spinal cord).
Risk Factors for Acute Lymphocytic Leukemia
No one knows the exact causes of acute lymphocytic
leukemia, and doctors can seldom explain why one person will get ALL and another person will not. However,
leukemia research has shown that people with certain risk factors are more likely than others to develop acute lymphocytic leukemia. A risk factor is anything that increases a person's chance of developing a disease.
- Being male
- Being white
- Being older than 70 years of age
- Past treatment with chemotherapy or radiation therapy
- Exposure to atomic bomb radiation
- Having a certain genetic disorder, such as Down syndrome.
Risk factors for childhood acute lymphocytic leukemia can include:
- Having a brother or sister with leukemia
- Being Caucasian or Hispanic
- Living in the United States
- Being exposed to x-rays before birth
- Being exposed to radiation
- Past treatment with chemotherapy or other drugs that weaken the immune system
- Having certain genetic disorders, such as Down syndrome.
Like all blood cells,
leukemia cells travel through the body. Depending on the number of abnormal cells and where these cells collect, patients with acute lymphocytic leukemia may have a number of symptoms of acute lymphocytic leukemia.
Diagnosing Acute Lymphocytic Leukemia
Tests and procedures that may be used to diagnose acute lymphocytic
leukemia include:
- Physical exam and history
- Complete blood count
- Peripheral blood smear
- Bone marrow aspiration and biopsy
- Cytogenetic analysis
- Immunophenotyping.
Physical Exam and History
A physical exam entails an exam of the body to check general signs of health, including checking for signs of disease, such as lumps or anything else that seems unusual. A history of the patient's health habits and past illnesses and treatments will also be taken.
Complete Blood Count (CBC)
A complete blood count is a procedure in which a sample of blood is drawn and checked for:
- The number of red blood cells, white blood cells, and platelets
- The amount of hemoglobin (the protein that carries oxygen) in the red blood cells
- The portion of the blood sample made up of red blood cells.
Peripheral Blood Smear
A peripheral blood smear is a procedure in which a sample of blood is checked for:
- The presence of blast cells
- The number and kinds of white blood cells
- The number of platelets
- Changes in the shape of blood cells.
Bone Marrow Aspiration and Biopsy
A bone marrow aspiration and biopsy entails the removal of a small piece of bone and bone marrow by inserting a needle into the hipbone or breastbone. A pathologist will then view both the bone and bone marrow samples under a microscope to look for abnormal cells.
Cytogenetic Analysis
A cytogenetic analysis is a test in which the cells in a sample of blood or bone marrow are looked at under a microscope to find out if there are certain changes in the chromosomes in the lymphocytes. For example, doctors will find that part of one chromosome has moved to another chromosome. This is called the Philadelphia chromosome.
Immunophenotyping
Immunophenotyping is a test in which the cells in a sample of blood or bone marrow are looked at under a microscope to find out if malignant (cancerous) lymphocytes began from the B lymphocytes or the T lymphocytes.
Once a person has been diagnosed with acute lymphocytic
leukemia, tests are done to find out if the cancer has spread to the central nervous system (brain and spinal cord) or to other parts of the body. The extent or spread of cancer is usually described in stages. It is important to know whether the leukemia has spread outside the blood and bone marrow in order to plan the appropriate ALL treatment.
There is no standard staging system for adult or childhood acute lymphocytic leukemia. For adults, acute lymphocytic leukemia is classified as untreated, in remission, or recurrent.
For childhood acute lymphocytic leukemia, risk groups are used instead of stages. Risk groups for childhood acute lymphocytic leukemia include:
- Standard (low) risk
- High risk
- Recurrent.
Treatment for Acute Lymphocytic Leukemia
Different types of treatment are available for patients with acute lymphocytic
leukemia. Some types of treatment are standard (the currently used treatment), and some types of treatment are being tested in clinical trials.
- Chemotherapy
- Radiation therapy
- Chemotherapy with stem cell transplant.
There are also three phases of ALL treatment, which include:
- Induction therapy
- Consolidation/intensification therapy
- Maintenance therapy.
Current adult acute lymphocytic treatment options include:
- Chemotherapy
- Radiation therapy
- Chemotherapy with stem cell transplant.
There are also two phases of adult acute lymphocytic leukemia treatment, which include remission induction therapy and maintenance therapy.
Choosing the most appropriate acute lymphocytic leukemia treatment is a decision that ideally involves the patient, the family, and the healthcare team.
The improvement in survival for childhood acute lymphocytic
leukemia over the past 35 years is one of the great success stories of cancer treatment. In the 1960s, less than 5 percent of children with acute lymphocytic leukemia survived for more than five years. Today, approximately 85 percent of children with acute lymphocytic leukemia live 5 years or more.
The chance of survival for children with ALL is dependent upon a number of factors. The most important factor is receiving optimal care at a center experienced in the treatment of childhood acute lymphocytic leukemia. Even with optimal care, however, some children with ALL are much more difficult to treat successfully than others. It is also now clear that the patient's subtype of ALL has a powerful impact on survival.
The prognosis (chance of recovery) for acute lymphocytic leukemia will depend on:
- The age of the patient
- Whether the cancer has spread to the brain or spinal cord
- Whether the Philadelphia chromosome is present
- Whether the cancer has been treated before or has recurred (come back).
(Click Acute Lymphocytic Leukemia Death Statistics for more information.)
Key information about acute lymphocytic leukemia includes:
- Acute lymphocytic leukemia (ALL) is a type of cancer in which the bone marrow makes too many lymphocytes (a type of white blood cell).
- With the exception of prenatal exposure to x-rays and specific genetic syndromes, such as Down syndrome, little is known about the causes of and risk factors for acute lymphocytic leukemia.
- Tests that examine the blood and bone marrow are used to detect and diagnose acute lymphocytic leukemia.
- Certain factors affect prognosis and treatment options for acute lymphocytic leukemia.
- The American Cancer Society estimated that 3,970 people in the United States (2,180 men and 1,790 women) would be diagnosed with acute lymphocytic leukemia in 2005.
