By Cat Troiano
In the United States alone, nearly 400,000 individuals are either currently living with leukemia or in remission, and more than 60,000 additional individuals are projected to be newly diagnosed with the disease during 2019. Although leukemia is most commonly diagnosed in adult patients over the age of 60, it is the most commonly diagnosed form of childhood cancer in patients under the age of 20. In fact, one out of every three cancer cases in children and teens is leukemia.
What Is Leukemia?
Leukemia is one form of blood cancer. Other examples of blood cancer include:
- Myelodysplastic syndromes
- Myeloproliferative neoplasms
More specifically, leukemia is a form of cancer that affects the body’s tissues that are responsible for the production of blood cells, namely the marrow component in bone as well as the lymphatic system.
Leukemia typically affects the production of white blood cells, which are the group of cells responsible for boosting the immune system to fight off invading pathogens. The white blood cells are abnormally formed, and the number of leukocytes exceeds the normal level. When blasts, which are immature blood cells, are abnormal and multiply too rapidly, the disease is categorized as acute leukemia. These immature cells are unable to carry out normal cellular functions. Conversely, in the case of what is considered chronic leukemia, mature white blood cells multiply too quickly, but less rapidly than the replication of the immature cells in the acute scenario. Because they are mature cells, they are able to carry out some normal cellular functions for a short time. The abnormal white blood cells that replace healthy white blood cells are leukemia cells.
Types of Leukocytes
White blood cells are collectively known as leukocytes. There are five different types of leukocytes in the human body:
Neutrophils are the body’s initial responders to target and fight infection. With a lifespan of only hours, the body must produce approximately 100 billion neutrophils a day. Neutrophils account for roughly half of the body’s white blood cells.
Eosinophils, which account for up to five percent of the body’s white blood cells, are responsible for fighting invading pathogens, such as bacteria as well as parasitic infections. When an individual suffers from allergy symptoms, it is because their eosinophils mistakenly interpret allergens as pathogenic elements and are working overtime to combat them.
Basophils make up only one percent of the body’s white blood cells. Basophils contain histamine, which act as a vasodilator to promote blood flow to the body’s tissues. Heparin, which is an anticoagulant, is also found in basophils to balance out the clotting effect of platelets so that the blood doesn’t clot too rapidly. Basophils play a role in inflammation when the body launches an immune response, such as when an allergen prompts an asthma attack.
Lymphocytes are subdivided into two types, which are known as T-cells and B-cells. These two groups of cells work together to fight illnesses. The T-cells are the army that is responsible for destroying invading pathogens, and the B-cells are those responsible for producing antibodies to recognize and fight future threats of infection when the body is exposed to pathogens.
Monocytes are the cleanup crew of the immune system, targeting destroyed pathogens and dead cells to remove them from the body’s tissues. Monocytes make up between five and twelve percent of the body’s white blood cells, and they are the largest of these cells.
Lymphocytic leukemia affects the body’s lymphocytes, which are found in lymph, the fluid that circulates the lymphatic system from the body’s tissues through the lymph nodes to aid in removing toxins and impurities.
Myelogenous leukemia affects the myeloid cells, which are the cells that play a role in the bone marrow’s production of white blood cells as well as red blood cells, also known as erythrocytes, and platelets.
Types of Leukemia
Leukemia, like many cancers, occurs in a number of different forms. The four most common types of leukemia are:
- Acute lymphocytic leukemia (ALL) can affect any age group, but it remains the most commonly diagnosed form of leukemia in children.
- Chronic lymphocytic leukemia (CLL) is the most commonly diagnosed form of leukemia in adults aged 55 and older.
- Acute myelogenous leukemia (AML) can affect any age group, but it is the most commonly diagnosed acute form of leukemia in adults.
- Chronic myelogenous leukemia (CML) is considerably more prevalent in adult patients than in children.
There are other types of leukemia, such as myelodysplastic syndrome, hairy cell leukemia, chronic myelomonocytic leukemia, large granular lymphocytic leukemia, myeloproliferative disorder, acute promyelocytic leukemia and juvenile myelomonocytic leukemia, but these are rarer forms of the disease.
Acute leukemias develop rapidly and the presentation of symptoms comes on soon after the onset of the disease. Chronic leukemias can take years to develop and for symptoms to present.
Risk Factors and Symptoms
Leukemia occurs more frequently in men than in women, it is more common in Caucasian individuals than in African-Americans, and the risk for developing leukemia increases with advancing age.
Other definitive risk factors are still being determined. Some potential factors that may increase one’s risk for developing leukemia include:
- Prior chemotherapy or radiation treatment for another form of cancer
- Chemical exposure, such as to benzene and formaldehyde
- Genetic disorders, such as Down’s syndrome
- Family history
Patients with leukemia are at increased risk for infections and anemia. Signs and symptoms of leukemia include the following:
- Swollen lymph nodes
- Pale skin
- Unexplained weight loss
- Liver or splenic enlargement
- Frequent infections
- Bone pain
- Bruising and/or bleeding
- Abdominal swelling or discomfort
A complete blood count with differential test should be ordered for any patient who presents with any of these symptoms and carries any of the potential risk factors.
Testing for Leukemia Diagnosis
A complete blood count (CBC) with differential takes an inventory of each of the body’s blood cells, including the different types of leukocytes. This test may be used to detect the presence of a blood disease, to confirm the presence of a suspected blood disease, and to monitor the progression of the patient’s disease and efficacy of the patient’s disease treatment protocol.
The normal reference range for the total number of white blood cells (WBCs) in an adult patient is between 4,500 and 10,000 cells per mcL. The normal reference range for each type of WBCs in adult patients is as follows:
• Neutrophils – 2.0–7.0×109/l (40–80%)
• Lymphocytes – 1.0–3.0×109/l (20–40%)
• Monocytes – 0.2–1.0×109/l (2–10%)
• Eosinophils – 0.02–0.5×109/l (1–6%)
• Basophils – 0.02–0.1×109/l (< 1–2%)
Abnormally high white blood cell counts are indicative of infection, inflammation or a condition such as leukemia.
The normal reference range for red blood cells (RBCs) is:
- Males: 4.5 to 5.9 cells per mcL
- Females: 4.1 to 5.1 cells per mcL
Abnormally low red blood cell counts are indicative of anemia.
Hemoglobin is the oxygen-carrying protein component in blood. The normal reference range for hemoglobin (Hg or Hgb) is:
- Males: 14 to 17.5 gm/dL
- Females: 12.3 to 15.3 gm/dL
Hematocrit represents the percentage of the blood’s erythrocyte component. The normal reference range for hematocrit (Hct) is:
- Males: 41.5 percent to 50.4 percent
- Females: 36.9 percent to 44.6 percent
Mean corpuscular volume (MCV) evaluates the average size of the blood’s erythrocytes. The normal reference range for MCV is 80 to 95 fl.
The normal reference range for the blood’s platelet count is 150,000 to 450,000 platelets per mcL
The normal reference ranges for infants, children and teens vary, depending on the gender and age of each patient.
Abnormally elevated leukocyte counts in a leukemia-suspect patient should prompt the ordering of additional diagnostic tests, which may include any of the following to confirm the diagnosis, to determine the type of leukemia and to evaluate the extent of which the leukemia has advanced:
- Bone marrow biopsy and histopathology
- Lymph node biopsy and histopathology
- Spinal tap
- PET scan
- CT scan
As the disease advances, leukemia cells in the bloodstream accumulate in such organs as the liver, spleen, lymph nodes and other organs. Periodic comprehensive metabolic profiles should be ordered in conjunction with CBC with differential tests to monitor organ function, and additional diagnostic imaging tests, such as ultrasounds and magnetic resonance imaging, of any affected organs should also be considered.
Treatment and Prognosis
The treatment plan and prognosis for a leukemia case depends on the patient’s age, which type of leukemia the patient has and how far along the disease has progressed. Treatment options include:
- Radiation treatment
- Stem cell transplant
- Biologic therapy
- Targeted therapy
- Chimeric antigen receptor T-cell treatment
As research continues in an ongoing search for a cure, clinical trials for new treatment protocols may be available to qualifying patients. As with most health conditions, the earlier a diagnosis is made and treatment can be implemented, the higher the chances are for achieving remission, and early detection begins with laboratory testing.