Leukemia is a cancer that begins in the blood-forming (lymphoid) cells in the bone marrow. Most often, it affects white blood cells.
Healthy white blood cells normally grow and divide in an orderly fashion as needed by the body. Leukemia occurs when these cells are damaged and acquire DNA mutations that cause them to function poorly and reproduce at a rapid rate. The leukemic cells then build up in the bloodstream, eventually crowding out healthy blood cells and leaving the body susceptible to infection.
In the United States, leukemia accounts for approximately 3.5% of newly diagnosed cancer cases. Compared to children, adults are diagnosed at a far greater rate, particularly those aged 65 to 74.
There are four main types of leukemia, which are classified based on the cancer’s rate of progression and the blood cells affected. Acute types of leukemia grow very quickly, while chronic types tend to develop gradually over time. Also, in chronic leukemia, the leukemic cells mature partially, but not completely, and therefore do not function as effectively as healthy blood cells.
Leukemia may form in lymphoblasts or myeloid blasts in the bone marrow. These precursor cells play a role in the formation of new blood cells (hematopoiesis). Lymphoblasts give rise to lymphocytes involved in the immune system, while myeloid blasts mature into a broader range of blood cells with various functions, including red blood cells, platelets and most white blood cells.
Acute myeloid leukemia (AML)
The most commonly diagnosed type of leukemia in adults, AML is a fast-growing cancer that develops in myeloid blasts, causing those cells to mature into abnormal white blood cells. As the leukemic cells multiply, they can overwhelm the healthy cells in the bone marrow and blood and sometimes spread to other parts of the body.
Acute lymphocytic leukemia (ALL)
A fast-growing cancer that occurs more often in children than adults, ALL originates in lymphoblasts. As a result, the bone marrow produces an abundance of immature leukemic cells that do not develop into properly functioning lymphocytes.
Chronic myeloid leukemia (CML)
CML is relatively uncommon and typically affects older adults. Although the leukemic cells tend to grow faster and survive longer than healthy blood cells, CML doesn't completely interfere with the development of mature white blood cells, red blood cells or platelets. However, it usually causes healthy blood cell counts to be lower than normal.
Chronic lymphocytic leukemia (CLL)
CLL mainly affects older adults and accounts for approximately one-third of all leukemia cases. This slow-growing cancer originates in lymphoblasts.
Leukemia causes and risk factors
The precise causes of leukemia are not yet fully understood. However, scientists have identified certain risk factors, such as advanced age and exposure to ionizing radiation, which may play a role in its development.
Researchers continue to study certain genetic and environmental factors that may be linked to the cellular mutations that cause leukemia, including:
- Specific genetic conditions, such as Down syndrome and certain blood disorders
- Human T-lymphotropic virus (HTLV)
- Human immunodeficiency virus (HIV)
- Exposure to petrochemicals, such as benzene
- Alkylating chemotherapy agents administered to treat another type of cancer
- Smoking and other forms of tobacco use
Leukemia signs and symptoms
Leukemia symptoms can vary based on the type and stage of the cancer. Also, because acute types of leukemia tend to progress much more quickly than chronic types, their symptoms generally appear earlier and worsen faster. Some warning signs include:
- Flu-like symptoms, including fever, chills and body aches
- Night sweats
- Overwhelming weakness or fatigue
- Loss of appetite
- Severe or recurrent infections
- Easy bleeding and bruising
- Frequent nosebleeds
- Tiny red skin spots (petechiae)
- Swollen lymph nodes
- Enlarged liver or spleen
- Unexplained weight loss
- Bone pain or tenderness
Usually, a leukemia diagnosis is made through the analysis of a blood sample. This can be accomplished with a complete blood count (CBC) or flow cytometry. The latter is a highly sensitive technology that uses a laser beam to identify cell types.
Typically, bone marrow testing is performed in conjunction with blood testing because it provides additional information that can aid in confirming a leukemia diagnosis and planning treatment. When performing a bone marrow biopsy, a physician will use a long needle to remove a core of bone and a liquid sample. The bone sample will be microscopically examined by a pathologist and the liquid sample can be used for flow cytometry and molecular testing.
Through molecular testing, a physician can evaluate the chromosomes within a cell (cytogenetics) and identify chromosomal variations and cellular abnormalities. Certain cytogenetic abnormalities are specific to leukemia and their presence or absence can help the physician determine the best course of treatment, such as a particular chemotherapy regimen or bone marrow transplant.
Leukemia treatment can vary depending on the type and extent of the cancer and the patient’s age and overall health. Many patients benefit from a customized combination of:
- Chemotherapy - After being administered intravenously, injected or swallowed in pill form, powerful cancer-fighting drugs enter the bloodstream and circulate throughout the body to destroy leukemia cells or prevent them from multiplying.
- Immunotherapy (biologic therapy) - Special medications are taken to boost the power of the body’s immune system and harness its natural ability to fight leukemia.
- Targeted therapy - Drugs are designed in a laboratory to target specific molecules (such as proteins) in leukemic cells that are signaling the cells to grow or divide.
- Radiation therapy - High-energy beams or X-rays are generated by a machine (linear accelerator) and precisely directed to a cancer site or distributed throughout the body before a stem cell or bone marrow transplant.
- Stem cell or bone marrow transplant (hematopoietic cell transplant) - The cancerous blood-forming cells are destroyed by chemotherapy or radiation therapy and then replaced with new, healthy hematopoietic cells derived from the blood or bone marrow of the patient or a donor.
- Chimeric antigen receptor (CAR) T-cell therapy - The body’s natural infection-fighting T-cells are removed, re-engineered to fight leukemic cells and then reinfused into the patient.
Frequently asked questions (FAQs) about leukemia
The following FAQs-related articles provide additional information about leukemia:
- What is the difference between acute and chronic leukemia?
- What are the risk factors for the different types of leukemia?
- What are the environmental risk factors for leukemia?
- Who is most at risk for developing leukemia?
- What are the signs of leukemia?
- What are the early warning signs of leukemia in children?
- Three symptoms that you might not know are related to leukemia
- What do leukemia spots look like?
- How does leukemia affect the body?
- What tests are done to diagnose leukemia?
- Questions to ask after a leukemia diagnosis
- Five things to know about leukemia treatment
- Five ways to prepare for leukemia treatment
- What are the most likely side effects of leukemia treatment?
- Are clinical trials right for me?
Benefit from world-class care at Moffitt Cancer Center
Moffitt Cancer Center is a high-volume cancer center and the multispecialty team in our renowned Malignant Hematology Program has extensive experience in diagnosing and treating leukemia, including relatively uncommon types. We take an individualized approach to cancer treatment, determining the optimal course of action depending on the type and stage of the cancer as well as the patient’s unique characteristics and preferences.
If you would like to learn more, you are welcome to talk with a leukemia specialist in our Malignant Hematology Program. You can request an appointment by calling 1-888-663-3488 or submitting a new patient registration form online. We do not require referrals.