Leukemia is a cancer of the blood cells. There are several types of blood cells, including red blood cells (RBCs), white blood cells (WBCs), and platelets. Generally, leukemia refers to cancers of the WBCs. Two types of WBCs often involved in leukemia are granulocytes and lymphocytes.
White blood cells are a vital part of your immune system. They protect your body from invasion by bacteria, viruses, and fungi. WBCs also protect your body from abnormal cells and other foreign substances. In leukemia, the white blood cells have mutated. These mutant white blood cells may divide too quickly and eventually crowd out normal cells. Often, they do not function as normal WBCs.
Blood cells are made in the bone marrow. When WBCs leave the marrow, they are found in the lymph nodes and spleen. They also circulate throughout the blood and lymphatic systems.
The onset of leukemia can be acute (sudden onset) or chronic (slow onset). In chronic leukemia, cancer cells increase slowly. Early symptoms can be very mild. Acute leukemia develops quickly. Cancer cells increase rapidly and symptoms occur early.
Acute and chronic leukemia are also classified according to the cell type. Leukemia involving myeloid cells is called myelogenous leukemia. These cells are immature blood cells that would normally become granulocytes or monocytes. Leukemia involving lymphocytes is called lymphocytic leukemia. There are four main types of leukemia.
Acute Myelogenous Leukemia (AML) has a rapid onset. It can occur in children and adults. About 13,000 new cases of AML are diagnosed annually.
Chronic Myelogenous Leukemia (CML) has a slow onset and affects mostly adults. About 5,000 new cases of CML are diagnosed annually.
Acute Lymphocytic Leukemia (ALL) has a rapid onset and occurs mostly in children. 5,000 new cases of ALL are diagnosed annually.
Chronic Lymphocytic Leukemia (CLL) is slow in onset. It is most likely to affect people over the age of 55. It is very rarely seen in children. There are about 15,000 new cases of CLL diagnosed every year.
Hairy cell leukemia is another type of leukemia. It is very rare.
The causes of leukemia are not known. However, several factors have been identified which may increase your risk. These include:
- family history of leukemia
- smoking (AML)
- genetic disorders such as Down syndrome
- blood disorders - myelodysplastic syndromes are sometimes known as pre-leukemia
- prior treatment for cancer with chemotherapy or radiation
- exposure to high levels of radiation
- chemical exposures, such as to benzene
The symptoms of leukemia include:
- excessive sweating, especially at night
- fatigue and weakness that do not go away with rest
- unintentional weight loss
- bone pain and tenderness
- painless, swollen lymph nodes (especially in the neck and armpits)
- enlargement of the liver or spleen
- red spots on the skin (petechiae)
- bleeding and bruising easily
- fever or chills
- frequent infections
Leukemia can also cause symptoms in organs that have been infiltrated or affected by the cancer cells. For example, central nervous system involvement can cause:
- nausea and vomiting
- loss of muscle control
Leukemia can also involve the lungs, gastrointestinal tract, heart, kidneys, and testes.
Leukemia may be suspected if you have certain risk factors or symptoms. Then diagnosis begins with a complete history and physical examination. The physical exam looks for pale skin, tender bones, enlarged lymph nodes, and enlargement of the liver and spleen. Leukemia can not be fully diagnosed by physical exam. Instead, doctors will use blood tests, biopsies, and imaging studies to see if you have this cancer.
There are a number of different tests that can be used to diagnose leukemia:
Complete Blood Counts determine the numbers of RBCs, WBCs, and platelets in the blood. Looking at your blood under a microscope can also determine if the cells have an abnormal appearance.
Tissue biopsies can be taken from the bone marrow or lymph nodes to look for evidence of leukemia. These small samples can identify the type of leukemia and its growth rate. Biopsies of other organs such as the liver and spleen can show if the cancer has spread.
Flow Cytometry examines the DNA of the cancer cells and determines their growth rate.
Liver Function Tests show whether leukemia cells are affecting or invading the liver. These tests look for elevated liver enzymes and bilirubin levels. Bilirubin is a substance made by the liver from the breakdown of RBCs.
Lumbar puncture is performed by inserting a thin needle between the vertebrae of your lower back. This allows your doctor to collect spinal fluid and determine if cancer has spread to the central nervous system.
Imaging studies help doctors look for damage leukemia has caused in other organs. These may include:
- CT scan
- PET scan
- 2D echocardiogram
- pulmonary function tests
Once your leukemia is diagnosed, it will be staged. Staging helps your doctor determine your prognosis. AML and ALL are staged based on how cancer cells look under the microscope and the type of cell involved. ALL and CLL are staged based on the WBC count at the time of diagnosis. The presence of immature cells white blood cells (myeloblasts) in the blood and bone marrow is also used to stage AML and CML.
Leukemia is usually treated by a hematologist-oncologist. These are doctors who specialize in blood disorders and cancer. Treatment depends upon the type and stage of the cancer. Some slow growing forms of leukemia do not need immediate treatment. This is called “watchful waiting.” However, treatment of leukemia usually involves chemotherapy, radiation therapy, and possibly stem cell transplantation.
The cells in your bone marrow which make new blood are known as stem cells. Stem cell transplantation replaces your stem cells with cells from a healthy donor. This can keep your body from making more cancerous cells. The diseased bone marrow has to be destroyed before a stem cell transplant can be performed. Doctors do this with chemotherapy and radiation. Radiation therapy can be directed to a specific part of the body or applied to the entire body. This is known as whole body radiation.
Biological therapy can also be used to treat leukemia. It uses medications to boost your immune system. Targeted therapy uses drugs that take advantage of specific vulnerabilities in cancer cells. Imatinib (Gleevec) is a targeted drug that acts against a protein found in CML cells.
The long-term outlook for leukemia patients depends on the type of the cancer and the stage at diagnosis. The sooner the disease is diagnosed and the faster it is treated, the better the chance of recovery.
The following factors can negatively affect the prognosis of leukemia:
- older age
- high WBC or low platelet count
- past history of blood disorders
- enlargement of the liver or spleen
- presence of bone damage
- chromosome mutations