Myeloid leukemia is a type of malignancy that occurs in the blood and bone marrow. It attacks immature cells and spreads quickly in the absence of treatment. Usually, it is of two types - acute myeloid leukemia (AML) with immediate onset and chronic myeloid leukemia (CML) which develops slowly. Risk factors associated with myeloid leukemia include age, sex, exposure to dangerous chemicals, previous treatment, smoking, other blood disorders, and familial predisposition. Although the exact etiology of myeloid leukemia is not known, it is evident that CML is brought on by abnormalities in a single chromosome (the Philadelphia chromosome), and AML is brought on by genetic mutations that cause the body to overproduce white blood cells. Early diagnosis and prompt treatment will improve the chances of survival in these patients.
Symptoms of acute myeloid leukemia include:
Weakness and lethargy
Bruises all over the skin.
Unusual bleeding, including frequent nosebleeds and gum bleeding.
Symptoms of chronic myeloid leukemia are:
Fatigue, weight loss, and night sweats.
Swelling and pain on the left side of the abdomen.
Feeling of fullness in the stomach after having a small meal.
Breathing difficulties and pale skin.
Rise in temperature
Readily bruising and bleeding.
There are several tests to detect myeloid leukemia. Age, general health of the patient, type of myeloid leukemia(acute or chronic), signs, and symptoms are the factors that are considered when selecting a diagnostic test. The following is the list of tests for the diagnosis of myeloid leukemia:
General history taking and physical examination: A proper medical, family, and occupational history of the patient is taken, and they are questioned about the symptoms experienced. They are also examined for any signs of the disease like the presence of tiny red spots on the skin (petechiae) and recurrent nosebleeds. Organs such as abdomen, lymph nodes, and spleen are also examined to detect any lumps or overgrowths that seems unusual.
Routine blood investigations: Routine lab tests can be carried out to determine the patients’ immunological status and the presence of risk factors. They include complete blood count, blood glucose test, lipid profile, thyroid function test, and urine analysis. In complete blood count, presence of immature white blood cells (myeloblasts) indicates the presence of leukemia.
Bone marrow biopsy and aspiration: Blood investigations will only indicate the presence of leukemia. To confirm the type of leukemia, a piece of tissue is taken from the larger bone(usually pelvis or hip) for histopathological examination and liquid is aspirated from the same with the help of the needle. When examined under microscope, sudden appearance or uncontrolled growth of myeloblasts is seen in acute myeloid leukemia (more than 20% of myeloblasts), whereas in chronic myeloid leukemia, there will be constant number of these myeloblasts.
Genetic tests: Samples of blood or bone marrow are examined using specialized assays to determine whether the BCR-ABL gene or the Philadelphia chromosome are present. These tests could use immunohistochemistry, flow cytometry, cytogenetics, and reverse transcription–polymerase chain reaction test (RT–PCR).
Imaging modalities: They may be used to help myeloid leukemia patients in diagnosing other infections or to learn more about the causes of their symptoms. They are generally not recommended in this leukemia diagnosis, because the disease has frequently expanded throughout the bone marrow by the time it is identified. They include computed tomography (CT, used for staging of leukemia), magnetic resonance imaging and 18F-Fluorodeoxyglucose (FDG)-positron emission tomography (PET, used to evaluate the extent of leukemia).
A multidisciplinary team composed of medical oncologists, radiologists, radiation oncologists, and pathologists is most suited to manage the course of treatment. The stage and the cellular type of the cancer, the patient's general health, and any other co-morbid conditions associated with myeloid leukemia are the factors that help in deciding the choice treatment . The main treatment of myeloid leukemia comprises of:
Chemotherapy: The most frequently prescribed drugs for the treatment of this form of leukemia include cytarabine, daunorubicin, cladribine, fludarabine, mitoxantrone, etoposide, 6-thioguanine, hydroxyurea, methotrexate, 6-mercaptopurine, azacitidine, and dexamethasone. But care should be taken while prescribing these drugs, as they are associated with side effects such as hair loss, nausea, vomiting, diarrhea, constipation, low blood cell counts, and recurrent infections.
Radiotherapy: In patients with advanced or recurrent leukemia, preoperative radiation therapy is primarily utilized to reduce the burden of the disease. It has been utilized, primarily as an adjuvant treatment along with chemotherapy.
Chemoradiation: Combining chemotherapy and radiation therapy increases the effectiveness of both treatments. It is indicated in remission cases.
Chemotherapy with stem cell transplant: One of the adverse effects of chemotherapy is that it reduces the normal blood cell count. To overcome this, a stem cell transplant can be given after chemotherapy or radiotherapy. They are the immature blood cells that are extracted from the blood or bone marrow of the patient or a donor and are frozen and kept. After completion of the treatment(chemo/radiotherapy), these stored cells are thawed and given back to the patient by infusion. They replace the blood-forming cells and restore the normal cell count.
Targeted therapy: Targeted medications function differently and tend to have different adverse effects, compared to conventional chemotherapy treatments. They can occasionally supplement chemotherapy or be used in conjunction with it to enhance its effectiveness. Some of these medications that are helpful for myeloid leukemia patients are ivosidenib, enasidenib, olutasidenib, midostaurin, gilteritinib, gemtuzumab, and venetoclax.
Immunotherapy: For the treatment of high-risk, early-stage leukemia, immunotherapeutic drugs are recommended for myeloid leukemia patients. Examples are monalizumab (protein kinase inhibitor),monoclonal antibodies, and CAR T -cell therapy. These medications inhibit a number of proteins that aid in cell growth, either directly or indirectly by encouraging angiogenesis (formation of new blood vessels).
Myeloid leukemia can be somewhat controlled with all these treatment options, but it cannot be cured completely. The stage of the disease affects the overall prognosis. Moreover, numerous environmental and genetic factors can also affect the development of this disease. So greater knowledge of these elements holds the prospect of preventing myeloid leukemia and helps in producing cutting-edge treatments.