Myeloid malignancies are a group of cancers that originate in the bone marrow, the soft, spongy tissue inside bones where blood cells are produced. These conditions involve the abnormal growth or function of specific types of blood cells. They are clonal diseases, arising from a single abnormal hematopoietic stem cell.
Understanding Myeloid Malignancies
The bone marrow houses hematopoietic stem cells that differentiate into various blood components, including red blood cells, white blood cells, and platelets. Myeloid malignancies develop when these myeloid stem cells undergo genetic or epigenetic changes, leading to uncontrolled proliferation and impaired differentiation. This abnormal growth results in an accumulation of immature or dysfunctional cells, which interferes with the normal production of healthy blood cells by crowding them out, leading to a reduction in red blood cells, white blood cells, and platelets.
Common Types of Myeloid Malignancies
Myeloid malignancies encompass several distinct conditions, each with unique characteristics. Acute Myeloid Leukemia (AML) is an aggressive cancer characterized by the rapid growth and accumulation of immature myeloid cells, called myeloblasts, in the bone marrow and blood. Chronic Myeloid Leukemia (CML) is a slower-progressing cancer involving the overproduction of mature granulocytes, a type of white blood cell. Most individuals with CML have an abnormal gene called BCR-ABL, which promotes the uncontrolled growth of these cells.
Myelodysplastic Syndromes (MDS) are disorders where the bone marrow’s stem cells are defective, leading to ineffective production of healthy blood cells and low blood counts. While considered cancers, MDS can progress to AML in some cases. Myeloproliferative Neoplasms (MPN) involve the overproduction of one or more types of blood cells—red blood cells, white blood cells, or platelets. Examples include Polycythemia Vera (PV), where too many red blood cells are produced, and Myelofibrosis (MF), where scar tissue replaces bone marrow, hindering blood cell production.
Recognizing the Signs and Diagnosis
Symptoms of myeloid malignancies arise from the reduction in normal blood cells and include fatigue, weakness, and paleness due to a low red blood cell count (anemia). A decrease in normal white blood cells leads to frequent or persistent infections and slow healing. A low platelet count causes easy bruising, unexplained bleeding from the nose or gums, or small red spots on the skin. Other general signs include fever, unexplained weight loss, night sweats, and bone or joint pain. An enlarged spleen, which causes discomfort or fullness in the upper left abdomen, is a symptom.
Diagnosis begins with a complete blood count (CBC) to assess the levels of different blood cells. Abnormalities, such as an excess of white blood cells, or low red blood cell and platelet counts, indicate a myeloid malignancy. A blood film, where a sample of blood is examined under a microscope, reveals abnormal cells like leukemic blasts. A definitive diagnosis requires a bone marrow biopsy, which involves taking a small sample of bone marrow for microscopic examination. Genetic testing on blood or bone marrow samples is performed to identify chromosomal abnormalities or gene mutations, which helps determine the type of malignancy and guide treatment decisions.
Treatment Approaches
Treatment for myeloid malignancies is individualized, depending on the malignancy type, stage, and patient’s overall health. Chemotherapy is a common approach, administered in phases such as induction and consolidation. Induction therapy aims to reduce the number of cancerous cells to an undetectable level, while consolidation therapy seeks to eliminate any remaining disease to achieve a sustained remission. Different chemotherapy regimens, sometimes involving drug combinations, are used.
Targeted therapy uses drugs that block or inhibit abnormal proteins or pathways within cancer cells, identified through genetic testing. Certain targeted drugs focus on gene mutations that regulate blood cell development. These therapies aim to be more precise than traditional chemotherapy, leading to fewer side effects.
Stem cell transplantation, or bone marrow transplantation, involves replacing diseased bone marrow with healthy blood-forming stem cells. This procedure follows high-dose chemotherapy that eliminates the patient’s own bone marrow. The healthy stem cells can come from a matched donor (allogeneic transplant) or from the patient’s own previously collected stem cells (autologous transplant).
Supportive care measures are integrated throughout the treatment process to manage symptoms and complications. This includes blood transfusions to address anemia (low red blood cells) or thrombocytopenia (low platelets), and antibiotics or antifungals to prevent or treat infections due to suppressed immune function. The overall treatment strategy is tailored to each individual, considering age, disease characteristics, and specific genetic changes.