Leukemias

Acute myeloid leukemia

Acute myeloid leukemia (AML) usually starts from cells that ultimately give rise to white blood cells (other than lymphocytes), red blood cells and the cells that make platelets. AML starts in the bone marrow, the spongy inner part of some bones where new blood cells are made. The “acute” in AML means that it can progress quickly without treatment.

Diagnosing AML

In addition to a physical exam, blood, bone marrow and genetic tests may be used to diagnose AML. These can include the following:

  • Complete blood count (CBC) measures the number of white blood cells, red blood cells and platelets in the blood.
  • Bone marrow aspiration and biopsy are often done at the same time. During these procedures, bone marrow tissue samples are removed for examination. A bone marrow biopsy involves removal of a sample of the bone along with the marrow from within the bone (usually the pelvic bone). For bone marrow aspiration, liquid bone marrow only is removed, usually from the back of the pelvic bone or breastbone.
  • Flow cytometry helps identify the type of leukemia by indicating the presence of substances associated with different leukemia cells.
  • Cytogenetic and genetic tests help determine whether chromosomal and genetic changes exist in the AML cells.

Imaging tests, such as computed tomography (CT), magnetic resonance imaging (MRI), ultrasound and X-ray are not necessary to diagnose AML but may be done to look for infections or other problems or help determine the extent of the disease.

Classifying AML

Most types of cancer are staged, which means they are assigned a category based on the tumor size and how far the cancer has spread. Knowing the stage of a cancer helps doctors choose the best treatment and determine a patient’s prognosis (prediction of the outlook).

AML usually does not form tumors, so it is not staged like most other cancers. Instead, it is classified into different subtypes based on the appearance of the leukemia cells, as well as the presence or absence of certain mutations or chromosomal changes. Knowing the subtype of AML can help doctors choose treatment and determine the prognosis. Two main systems are used to classify AML: the French-American-British (FAB) classification and the newer World Health Organization (WHO) classification.

FAB divides AML into seven subtypes, M0 through M7, based on the type of cell the leukemia started in and how mature the cells are. The WHO classification system takes into account more factors that can affect prognosis and is used more commonly than the FAB classification. The WHO system classifies AML into the following groups:

  • AML with certain genetic abnormalities
  • AML with myelodysplasia-related changes
  • AML related to previous chemotherapy or radiation therapy
  • AML not otherwise specified
  • Myeloid sarcoma
  • Myeloid proliferations related to Down syndrome
  • Undifferentiated and biphenotypic acute leukemias

Treating AML

After AML is diagnosed and classified, your medical team will work with you to choose the best treatment option for you. The main treatment for AML is chemotherapy, sometimes with stem cell transplantation. In certain rare circumstances, radiation therapy may also be used to treat AML. Since AML can progress quickly, treatment should start as soon as possible. Participating in a clinical trial is something that should definitely be considered by you and your physician.

Chemotherapy

Chemotherapy is the main treatment for AML. Chemotherapy drugs, also called cytotoxic drugs, are used to stop the growth of cancer, either by killing cancer cells or by preventing them from dividing and growing. Chemotherapy is considered a systemic treatment because the drugs travel throughout the body in the bloodstream.

Chemotherapy for AML is usually given over two distinct phases. Induction is the first phase of treatment and is designed to kill leukemia cells, clearing the blood of them. In the second phase, consolidation, chemotherapy is given after the patient has recovered from induction. The goal of consolidation chemotherapy is to kill the few remaining leukemia cells that are still present but cannot be detected because their level is low.

For some people with acute promyelocytic leukemia (APL) (the M3 subtype of AML) who are at a higher risk for relapse, a third phase called maintenance is often given. It involves low doses of oral chemotherapy drugs for up to two years after the consolidation phase ends.

The initial chemotherapy drugs often used to treat AML include cytarabine, daunorubicin (Cerubidine) or idarubicin (Idamycin). Treatment for APL differs. It initially requires treatment with all-trans-retinoic acid (ATRA) and either idarubicin or arsenic trioxide (Trisenox).

Stem cell transplantation

Stem cell transplantation (also known as a bone marrow transplant) is an infusion of healthy stem cells into the body. After a person receives high-dose chemotherapy to kill the cancer cells, a transplant can occur. The healthy cells can be collected from blood or bone marrow from the patient. It can also be collected from umbilical cord blood, a family member or another donor.

An autologous stem cell transplant is a transplant of the patient’s own stem cells, from either the bone marrow or blood. In an allogeneic stem cell transplant, the stem cells come from a volunteer donor whose tissue type closely matches that of the patient. If available, a sister or brother offers the best chance of a close match. If a sibling or another family member is not a good match, an unrelated volunteer donor may be found through a national registry.

Using the patient’s own stem cells could reintroduce leukemia cells, so allogeneic stem cell transplants are the preferred type of stem cell transplants for people with AML. Allogeneic transplants are associated with serious risks, so they are usually used for people who are relatively healthy other than the leukemia.

Radiation therapy

Radiation therapy is rarely used to treat AML but may be appropriate in some cases. This treatment, which uses high-energy X-rays and other particles to kill cancer cells, may be used for AML that has spread to the brain and spinal fluid or the testicles.

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