What is Acute Lymphocytic Leukemia (ALL)?
Acute lymphocytic leukemia (ALL) is a cancer that affects the bone marrow and the blood. ALL may also be called acute lymphoblastic leukemia or acute lymphoid leukemia.
This blood cancer begins in the lymphoid cells, which can become B cells, T cells, and natural killer cells. "Acute" means that this type of cancer grows fast and can progress quickly if not treated. However, many types of ALL tend to respond well to treatment.1,2
Each of these blood cells are created in the bone marrow, the spongy center of bones. The bone marrow contains blood stem cells. These are immature cells that can become different types of cells in the body. Stem cells can be myeloid cells or lymphoid cells. Lymphoid cells become cells such as B cells, T cells, and natural killer cells.
How does ALL develop?
The cells that make up the blood, including white blood cells, red blood cells, and platelets, are made in the bone marrow. When a lymphoid cell becomes cancerous, it multiplies and crowds out normal, healthy cells. ALL begins in the bone marrow, but it can quickly spread to other areas of the body, including the central nervous system and the lymph nodes.1,2
ALL is a blood cancer that begins in the lymphoid cells, and ALL can be divided into subtypes including B cell leukemias and T cell leukemias.2-4
How genes impact ALL
A gene is a segment of DNA that is passed from parent to child. Genes are arranged into structures called chromosomes, and each person has 23 pairs of chromosomes.5 Each time any cell in the body divides, it makes a new copy of its DNA. Sometimes errors occur during this division.1
These errors can cause a cell to grow abnormally. This may lead to cancer if cells called oncogenes are turned on or tumor suppressor genes are turned off. Oncogenes can cause the cells to replicate more, which can result in cancer. Tumor suppressor genes are normally a stop mechanism that cause damaged cells to die or slow cell growth. When tumor suppressor genes are turned off, cancer cells can divide and grown more easily.1
The Philadelphia chromosome
The Philadelphia chromosome is one of the most common DNA errors in people with ALL. It occurs in about 1 in 4 cases of ALL in adults.1
The Philadelphia chromosome is named for the city it was discovered in, and its discovery, in the 1960's, made it the first chromosomal abnormality conclusively linked to a type of cancer. If a person's cancer has the Philadelphia chromosome, it is called Philadelphia chromosome-positive ALL, or Ph+ ALL.6
Figure 1. Philadelphia chromosome
What are the different types of acute lymphocytic leukemia (ALL)?
There are several different types of ALL, and finding the type is important for treatment recommendations. There are two main subtypes: B cell ALL and T cell ALL. Each is named for the type of white blood cell they develop from. Most cases of ALL are B cell ALL.2
Additional types of ALL include:
- Acute B lymphoblastic leukemia
- Early precursor B ALL (also known as early pre-B ALL or pro-B ALL)
- Common ALL
- Pre-B ALL
- Mature B cell ALL (also known as Burkitt leukemia)
- Philadelphia-positive ALL (Ph+ ALL)
- Acute T-lymphoblastic leukemia
- Natural killer cell leukemia1,2
Who gets acute lymphocytic leukemia (ALL)?
ALL is more common in children than adults, with more than 50 percent of cases occurring before age 20. The risk of ALL is greatest in children younger than 5 years old. The risk declines after age 5 until the mid-20s. Other groups that have a greater risk of ALL are adults between ages 20 and 34 and 55 to 64.1,6
ALL is slightly more common in males than females. It is more common in whites and Hispanics than African Americans, Asian Americans, and Native Americans.1
Risk factors for acute lymphocytic leukemia
Risk factors are things that may increase someone's chances of developing a disease, like ALL. Only a few risk factors for ALL are known, including:
- Being exposed to chemotherapy or radiation, including from treatment for another cancer
- Exposure to some chemicals, like benzene (found in gasoline, the rubber industry, the chemical industry, cigarette smoke, and some cleaning products)
- Some viral infections, including human T cell lymphoma/leukemia virus-1 (HTLV-1) or Epstein-Barr virus (mononucleosis or "mono")
- Genetic disorders, like Down's syndrome, Klinefelter syndrome, Fanconi anemia, Bloom syndrome, ataxia-telangiectasia, or neurofibromatosis
- Being male
- Being white or Hispanic
- Having an identical twin with ALL1,2
What are common symptoms of acute lymphocytic leukemia (ALL)?
The crowding out of the healthy blood cells by ALL can cause problems such as:
- Anemia, a lack of red blood cells, which can cause fatigue
- Neutropenia, a lack of neutrophils (a type of white blood cell) that puts a person at risk of infections
- Thrombocytopenia, a lack of platelets that puts a person at risk for bleeding or bruising
- Pancytopenia, a lack of all three: red blood cells, white blood cells, and platelets2
These complications can create symptoms of:
- Frequent bruises, especially without a reason (like a fall or bump)
- Fatigue, weakness, or tiredness
- Repeated infections, or infections that don't go away
- Dizziness or feeling lightheaded
- Easily bleeding, such as from cuts, from the gums, or frequent nose bleeds
- Shortness of breath
- Achiness in the arms, legs, or hips
- Weight loss with no apparent reason1,2
How does acute lymphocytic leukemia progress (ALL)?
As an acute leukemia, ALL can progress very quickly. The type of damaged lymphoid cell that becomes cancerous is called a leukemic lymphoblast. These can grow rapidly and can block the production of normal blood cells.
The leukemic cells fill the blood and bone marrow and can progress to the lymph nodes, spleen, liver, central nervous system (the brain and spinal cord), and potentially the testicles in males. Because ALL can progress so quickly, treatment is usually begins soon after diagnosis.2
How is acute lymphocytic leukemia (ALL) staged?
A standard staging system does not exist for ALL.2 ALL is generally classified by its subtype, which helps guide treatment decisions. B cell ALL and T cell ALL are the two main subtypes, named for the type of white blood cell they develop from.
What is the prognosis for acute lymphocytic leukemia (ALL)?
While most cases of ALL happen in children, 4 out of 5 deaths from ALL occur in adults. This may be due to differences in the cancer between children and adults. Or, it may be because children’s bodies can often tolerate more aggressive treatment than adults.1-6
Over the past few decades, the survival rate for all leukemias, including ALL, has steadily increased. Based on data from 2009-2015, the National Cancer Institute has determined the 5-year survival rate for ALL overall is 68.6 percent, and the 5-year survival rate for children and adolescents (younger than 15 years) with ALL is 91.8 percent.2,6
Survival rates are based on previous outcomes of people who survive a certain amount of time after diagnosis. In cancer estimates, experts use the “5-year survival rate” as a marker. It is important to keep in mind that many people live more than 5 years after diagnosis. These statistics do not necessarily predict what will happen for any single person.