Acute Myeloid Leukemia Types / AML Types
Acute Myeloid Leukemia is a cancer of the blood and bone marrow. This fast growing cancer starts in the bone marrow when blasts, cells that are not fully formed, are created. Normally, these blasts would form white blood cells that would help the body to fight off infections, however, in patients with AML these blasts never fully mature.
According to the American Cancer Society, “Bone marrow is made up of blood-forming cells, fat cells, and supporting tissues that help the blood-forming cells grow. A small fraction of the blood-forming cells are a special type of cell known as stem cells. Stem cells are needed to make new cells. When a stem cell divides, it makes 2 cells: one cell that stays a stem cell and another cell that can keep changing and dividing to make blood cells.” These stem cells form the three types of blood cells: red blood cells, white blood cells and platelets. AML affects the normal production of these cells.
As AML progresses the bone marrow may also begin to make abnormal platelets and red blood cells. These abnormal cells begin to outnumber the normal, healthy cells. Many of the symptoms of AML are actually a result of these changes in the blood cells. Frequent infections can develop as a result of the decrease in the white blood cells. Anemia can develop from the lower number of red blood cells carrying oxygen to the different parts of the body. Bruising or a tendency to bleed can result from the low numbers of fully developed platelets. Joint and bone pain is also a common symptom that results from the increase in the number of abnormal blood cells.
While AML starts in the bone marrow and blood, it can spread to and affect other areas of the body. Treatment may include addressing both the underlying cancer and the symptoms that are caused by the spread of the leukemia through the bloodstream into the organs of the body. New research is helping to inform the treatment of AML and increase the options for each patient in the healthcare system.
How many different types of AML are there?
AML can be called a variety of names, which is sometimes confusing for patients. Acute refers to the quick onset of the disease. Leukemia is a cancer of the blood forming tissues. The middle terms of each type of leukemia gives more meaning to the type of AML. However, if we examine the meaning of each of these terms, it makes sense why all of these refer to the same cancer:
Acute myelocytic leukemia
A myelocyte is simply a bone-marrow cell. According to Webster’s Dictionary, a myelocyte is “a motile cell with cytoplasmic granules that gives rise to the granulocytes of the blood and occurs abnormally in the circulating blood.”
Acute myelogenous leukemia
Myelogenous is defined as relating to, or produced by the bone marrow. The white blood cells are sometimes referred to as myeloid cells. These myeloid cells are what normally develop into the three types of blood cells – white blood cells, red blood cells and platelets.
Acute granulocytic leukemia
A granulocyte is any of a group of white blood cells that destroy bacteria. This includes the basophils, eosinophils, and neutrophils.
Acute nonlymphocytic leukemia
A lymphocyte is an immune cell that is made in the bone marrow. Some lymphocytes create antibodies for your body’s immune defenses. Other lymphocytes kill the germs directly. Nonlymphocytic means that the leukemia does not affect these immune cells.
Acute promyelocytic leukemia
Promyelocytes are immature white blood cells. APL is characterized by the overproduction of these promyelocytes and consequently, the underproduction of healthy white blood cells. APL is an aggressive form of acute myeloid leukemia and typically occurs in middle-aged adults and occurs because of a change in a person’s chromosomes. This change creates a specific protein which can be detected through a blood test. This blood test is how APL is diagnosed.
How is AML classified?
One of the main differences in AML and other cancers is that AML has 8 different subtypes. The French-American-British classification system of subtypes is based on where the leukemia cells develop and how mature the leukemia cells are. This is the most common classification system for leukemia used in the United States. It is important to know the subtype of AML that you have been diagnosed with as this will affect both the treatment options that your healthcare provider outlines, and the overall outlook of the cancer prognosis. Certain subtypes respond better to various AML Treatments.
The 8 Subtypes of the FAB System:
- M0 AML: Undifferentiated acute myeloblastic leukemia.
- M1 AML: Acute myeloblastic leukemia with minimal maturation
- M2 AML: Acute myeloblastic leukemia with maturation
- M3 AML: Acute promyelocytic leukemia (APL)
- M4 AML: Acute myelomonocytic leukemia
- M4 AML eos: Acute myelomonocytic leukemia with eosinophilia
- M5 AML: Acute monocytic leukemia
- M6 AML: Acute erythroid leukemia
- M7 AML: Acute megakaryoblastic leukemia
The World Health Organization also developed a classification system that tries to include newly discovered factors that can affect prognosis and treatment. The WHO divides AML into several groups based on the chromosome or gene affected by the cancer and is a much more extensive classification system.
The WHO Subtypes are:
- AML with certain recurrent genetic abnormalities (gene or chromosome changes)
- AML with myelodysplasia-related changes
- AML related to previous chemotherapy or radiation
- AML not otherwise specified
- Myeloid sarcoma (also known as granulocytic sarcoma or chloroma)
- Myeloid proliferations related to Down syndrome
- Blastic plasmacytoid dendritic cell neoplasm
- Acute leukemias of ambiguous lineage
- Myeloid neoplasms with germline predisposition
- Undifferentiated and biphenotypic acute leukemias are not strictly AML, but are leukemias that have both lymphocytic and myeloid features. They are sometimes called mixed phenotype acute leukemias (MPALs).
Can AML spread? Which parts of the body are typically affected by this cancer?
AML is a type of cancer that can spread to other parts of the body. While AML starts in the bone marrow and blood cells, the progression of the disease involves spreading to the lymph nodes, organs, cerebral spinal fluid, liver, skin, spleen, spine and brain.
How is acute myeloid leukemia diagnosed?
When a physician suspects acute myeloid leukemia as the cancer, they may perform a variety of tests to look for chromosome abnormalities and the composition of the patient’s blood. Antigens, a specific protein that appears on the surface of leukemia cells, are also sometimes created in patients with AML and can be measured through simple blood tests.
The average age of diagnosis is 72, and this cancer is more prevalent in men than women.
What is the most common type of Acute Myeloid Leukemia Treatment?
Because AML is a cancer, chemotherapy is the most common treatment for acute myeloid leukemia. A stem cell transplant may be used in conjunction with or autonomously from the chemotherapy treatment. Radiation therapy to target leukemia cells in specific parts of the body may be used again as either a stand alone treatment or also in conjunction with a stem cell transplant.
Immunotherapy is another type of cancer treatment sometimes utilized in the treatment of acute myeloid leukemia. This biological therapy is designed to help the immune system to fight infections and other diseases.
Finally, Sierra Trial is investigating the use of 131I apamistamab (Iomab-B) in patients age 55+ with active, relapsed or refractory Acute Myeloid Leukemia (AML), to enable bone marrow transplant (BMT). This innovative new drug therapy is currently awaiting approval by the FDA.
The type of treatment you receive and your treatment outcome depend on your individual risk factors and the subtype of AML being treated. The number of adults and their remission lengths have grown significantly over the past 30 years.
What are Other Common Types of Leukemia?
All cancer starts when cells begin to grow uncontrollably and then start to spread to other parts of the body. All leukemias are a hematologic (blood) cancer as opposed to a solid tumor cancer. Leukemia starts in the blood or bone marrow before it spreads to other parts of the body. The main difference in the various types of leukemia involve how quickly the disease progresses (acute vs chronic) and which cells of the blood and bone marrow are affected first.
Acute Lymphocytic Leukemia
Acute lymphocytic leukemia (ALL) is a rare cancer of the blood that progresses very quickly as the immature blood cells (blasts) take over a patient’s bone marrow. Lymphoid cells are cells that normally develop into lymphocytes, a type of white blood cell. The symptoms of ALL are very similar to acute myeloid leukemia symptoms. The main difference is that in AML, the bone marrow is taken over by myeloid blasts, whereas in ALL lymphoid blasts take over the bone marrow.
Chronic Lymphocytic Leukemia
Chronic lymphocytic leukemia (CLL) is the most common type of leukemia in adults. It is a slow building cancer, and as such, many people don’t have symptoms for at least a few years. Like ALL, CLL produces immature lymphoid cells that should have formed normal lymphocytes. Eventually the lymphoid blasts begin to grow and spread to other parts of the body including the lymph nodes, liver and spleen. The onset of this leukemia is slower than the onset of both AML and ALL.
Chronic Myeloid Leukemia
Chronic myeloid leukemia (CML) is also known as chronic myelogenous leukemia. CML occurs when the bone marrow produces abnormal granulocytes. Like AML, these white blood cells then affect other parts of the body as they travel through the bloodstream. The main difference between CML and AML is the time that it takes for the disease to progress. With AML, the onset of the cancer is acute or sudden. With CML, the onset of the cancer is more gradual.
Chronic Myelomonocytic Leukemia
Chronic myelomonocytic leukemia (CMML) mainly affects older adults. CMML is often characterized by a monocyte (a type of immune cell) count that is too high. According to the American Cancer Society, CMML develops into acute myeloid leukemia in about 15% – 30% of patients.
If I have AML, what questions should I ask my doctor?
If you’ve recently been diagnosed with one of these types of AML, you will have many questions related to your ongoing care. Here are a few that you should ask your healthcare provider as well.
- What subtype of AML do I have?
- What are the treatment options and outcomes for the different types of AML?
- What are the risks or side effects of each treatment option?
- What complications can arise from the treatment?
- What additional information do I need to decide on a course of treatment?