Acute Myeloid Leukemia (AML) is a malignant disease of the myeloid line of blood cells. It is characterized by the rapid growth of abnormal cells that build up in the bone marrow and blood, especially the myeloid cells. Myeloid cells generally develop into various types of mature blood cells like red blood cells, white blood cells, and platelets. This cancer rapidly progresses and is typically fatal within weeks or months if left untreated.
Causes and Risk Factors for Developing AML
The normal myeloid stem cells usually develop into red blood cells, granulocytes, or platelets. This process is regulated by certain signals generated in the body to ensure that an adequate number of blood cells are made. In AML, however, the myeloid stem cells become immature white blood cells (myeloblasts), abnormal red blood cells, or defective platelets. These cells, called leukemia cells or blasts, build up in the bone marrow and blood, leaving less room for healthy blood cells.
While the exact cause is yet to be ascertained, several factors which contribute to the development of AML have been discovered. Genetic mutations on chromosome 15 and the presence of the abnormal gene PML-RARA affects the maturation of the blood cells and may lead to AML. Other risk factors for the development of AML are:
- · Genetic disorders like Down syndrome, Bloom syndrome, Fanconi anemia, Li-Fraumeni syndrome, trisomy 8, and neurofibromatosis type 1.
- · High levels of radiation exposure,
- · Treatment with chemotherapeutic drugs like epipodophyllotoxins and cyclophosphamide,
- · Blood disorders like myelodysplastic syndrome, thrombocythemia, or polycythemia vera,
- · Exposure to chemicals like benzene, and
- · Smoking.
Signs and Symptoms of Acute Myeloid Leukemia
The early symptoms of Acute Myeloid Leukemia are similar to that of the flu or other common diseases. The characteristic signs and symptoms of AML are:
- · Generalized weakness
- · Anemia
- · Fatigue
- · Headache, vomiting, lethargy,
- · Paleness
- · Weight loss
- · Loss of appetite
- · Palpitations
- · Bleeding with minor trauma
- · Small blood vessels on the skin (Petechiae)
- · Pitting edema in lower limbs
- · Bleeding from the nose (epistaxis)
- · Shortness of breath
- · Mild and asymptomatic spleen enlargement
- · Vasculitis
- · Swelling of the gums
Diagnosis and Treatment of Acute Myeloid Leukemia
Screening tests
The screening tests used for diagnosing AML are (1), (2), (3), (4), (5) :
Ø Blood tests – These reveal the number of white blood cells, red blood cells, and platelets. Blood tests are commonly used to see the presence of leukemic blast cells, which is an indicator of acute myelogenous leukemia.
Ø Bone marrow test – A sample of the bone marrow is taken from the hipbone or breastbone via biopsy and tested for leukemia cells.
Ø Immunophenotyping – This is a laboratory test that uses antibodies to identify cancer cells based on the types of antigens or markers present on the surface of the cells. It helps diagnose specific types of leukemia.
Ø Flow cytometry – It is a laboratory test that gives an estimate of the number of cells in a sample and the percentage of live cells in a sample. The morphological features of the cells as well as the presence of tumor markers on the cell surface, can also be seen in this test.
Ø Spinal fluid test – Spinal tap or lumbar puncture test is carried out to determine whether the cancer cells have spread to the spinal fluid. Besides this, it is infrequently used for the delivery of chemotherapeutic drugs into the CSF to prevent or treat leukemia of the brain and spinal cord.
Treatment
The treatment of Acute Myeloid Leukemia falls into two phases, namely –
Ø Remission induction therapy – It is initiated to kill most of the leukemia cells in the blood and bone marrow. The main goal of this phase is to reach complete remission, which implies that no disease can be detected with the available diagnostic methods. The preferred drug of choice in this phase is cytarabine, along with anthracyclines like daunorubicin or idarubicin.
Ø Consolidation therapy – In this phase, the remaining leukemia cells that may not be active or could cause relapse are killed. It is crucial in ensuring the patients’ well-being as it controls the relapse of AML.
The treatment protocols for Acute Myeloid Leukemia are:
· Chemotherapy – This is the initial treatment of choice which combines multiple antileukemic drugs tailored to each person. Some of the commonly used chemotherapeutic drugs are vincristine, cytarabine + methotrexate, etoposide, mercaptopurine, etc.
· Radiation therapy – High-powered beams such as x-rays or protons are used to kill the cancer cells. It is often recommended as a part of the preparations for bone marrow transplants.
· Stem cell transplant or bone marrow transplant – During chemotherapy, the healthy cells, along with the tumor cells, get destroyed. Transplantation of healthy blood-forming cells, stem cells that are removed from the blood or bone marrow of the patient or a donor, is beneficial in restoring the body’s blood cells.
