Leukemia - Cancer Institute Overview
Blood and lymph node cancers
Cleveland Clinic Taussig Cancer Institute hematologists and medical oncologists provide diagnosis and treatment for patients with hematologic malignancies, including chronic and acute leukemia, Hodgkin’s and non-Hodgkin’s lymphoma, and multiple myeloma. They rely on the diagnostic expertise of Clinic pathologists who specialize in such areas as the lymphomas. Treatments offered include chemotherapy and biologic response modifier therapy, as well as bone marrow transplantation.
Cleveland Clinic Taussig Cancer Institute oncologists administer more than 18,000 courses of chemotherapy every year, often involving investigational drugs or drug combinations not available elsewhere. Their participation in the Southwest Oncology Group, Children’s Cancer Study Group, National Cancer Institute and other trials gives hematologic cancer patients access to more than 100 national trials. These group studies enhance the gathering of data on relatively rare cancers and expedite testing of new therapies for common cancers.
What is leukemia?
Leukemias are cancers of the blood and bone marrow cells. The bone marrow is responsible for producing most of our blood cells – similar to the way a factory may produce different parts. All of the blood cells start out from a single cell type called a stem cell (also called pleuripotential cells). Seven different types of cell lines develop from the stem cell, each of the types controlled by a specific growth factor.
When the stem cell divides, one of the “daughter cells” remains a stem cell and the other becomes either a lymphoid cell or myeloid cell (known as precursors). These cells will continue to mature into various blood cells, including red blood cells (erythrocytes) which deliver oxygen to the tissues; white blood cells (including basophils, eosinophils, neutrophils, lymphocytes and monocytes) which fight infections (this is your immune system); and platelets (thrombocytes) which help stop bleeding. Different types of leukemia can develop at any point during the process of stem cell maturation.
Leukemia may result in an overproduction of immature cells of a certain cell line, which then fill up the space in the bone marrow and can cause underproduction of other important cell lines. The type of cell that has become cancerous, as well as the number of these cells, helps to determine the type of leukemia (discussed in a later section).
What causes leukemia?
Most leukemias have no known cause. There is some evidence that people who have prolonged or significant exposure to radiation may be at higher risk to develop leukemia. There is also evidence that people who have been exposed to toxic chemical compounds (such as benzene) and certain types of chemotherapy may be at higher risk.
People with certain diseases of the bone marrow, such as myelodysplastic syndrome (MDS), myeloproliferative diseases (MPD), polycythemia vera (PV), or essential thrombocytosis (ET) are at higher risk for developing acute leukemia.
What are the symptoms of leukemia?
Many people with leukemia have no symptoms at all and are diagnosed during a routine medical examination. The doctor may find an enlarged lymph node or spleen. Likewise, the physical examination may be normal but there is an abnormality on a routine blood test (usually a complete blood count – CBC).
People who do have leukemia symptoms commonly complain of generalized weakness, fatigue, fevers (flu-like symptoms), frequent infections, and easy bruising or bleeding (often from the gums or nose). Some people may have enlarged lymph nodes or abdominal fullness or bone pain. Rarely, people will have a rash or headaches.
How is leukemia diagnosed?
Leukemia may be suspected if a person presents with any combination of the symptoms above. A complete blood count (CBC) blood test may further increase the doctor’s concern. The CBC may show abnormally high or abnormally low white blood cell counts. In addition, there may be abnormalities of the red blood cells or platelets. In some cases, there may be blasts (immature white blood cells) present in the CBC.
In most cases, the diagnosis of leukemia is confirmed by a bone marrow biopsy. Pathologists (doctors who look at tissue under the microscope) and hematologists (doctors specializing in blood diseases) will analyze the bone marrow and determine which type of cell has become cancerous and whether the leukemia is acute or chronic. In many cases, cytogenetic studies (studies of the genetic material in cells) may be done to provide additional information about the leukemia that will help the doctors determine the best treatments.
Leukemia is not staged numerically (I, II, III, or IV), the way many other cancers are staged, with the exception of chronic lymphocytic leukemia (CLL). Rather, its classification as acute or chronic will give some indication as to the seriousness of the disease. In addition, various prognostic factors, such as the blood counts, cytogenetics and persons general health will help to guide treatment decisions.
Types of leukemia and Treatment of leukemia
There are two main classifications of leukemia, acute leukemia and chronic leukemia. Within each of these categories, the cancerous cell type determines the type of either acute or chronic leukemia.
Acute leukemia is an aggressive, life-threatening disease. Acute leukemia is usually defined by a blast (immature white blood cell) count of greater than 20 percent in the bone marrow. Treatments that are given with the goal of curing the leukemia require intense chemotherapy, which may also have life-threatening complications in the medically frail (people who are not in good health).
The decision regarding what treatment will be pursued involves the doctor, patient and family based on the information about the disease and the expected response to therapy.
Acute myelogenous leukemia (AML)
Acute myelogenous leukemia (AML) is when the myeloid cell becomes cancerous. There are several subtypes of AML that are very similar in terms of prognosis and treatment. The patient who has been diagnosed with AML is usually hospitalized right away in order to start therapy. The usual treatment is intensive induction chemotherapy.
The goal of therapy is to achieve a remission (the bone marrow biopsy shows no evidence of leukemia). In most cases, it will take weeks before the results of therapy are known.
If there is a successful remission, the doctor will prescribe post-remission therapy – usually either more chemotherapy or bone marrow transplantation if a suitable donor is available and the benefits outweigh the risks. The length of initial hospitalization may be four to six weeks.
Acute promyelocytic leukemia (APL)
Acute promyelocytic leukemia (APL) is a subtype of AML that differs slightly from the other subtypes of AML. APL is associated with bleeding and will respond better when a specific drug (all-trans-retinoic acid – ATRA) is used in combination with standard chemotherapy.
Acute lymphocytic leukemia (ALL)
Acute lymphocytic leukemia (ALL) is the most common leukemia in children but may also occur in adults. In ALL, the lymphoid cells become cancerous. Treatment for acute lymphocytic leukemia includes induction chemotherapy with the goal of achieving remission (the bone marrow biopsy shows no evidence of leukemia).
If a remission is achieved, post-remission therapy will be done often followed by maintenance therapy. A bone marrow transplant may be considered in acute lymphocytic leukemia cases if there is a suitable donor available and the benefits outweigh the risks.
Chronic leukemia has a slower onset and is not usually life-threatening at the time of diagnosis. Chronic leukemia has a longer natural history, meaning that if the disease were untreated, people would survive significantly longer than those with acute leukemia. There are significant differences in the approaches to the various types of chronic leukemia.
Chronic myelogenous leukemia (CML)
Chronic myelogenous leukemia affects the myeloid cells. The disease usually affects people in their 50s and 60s but may affect a person at any age. The diagnosis of CML can be confirmed in most cases by the presence of an abnormal gene or chromosome - the Philadelphia chromosome.
There are three phases of CML: the chronic phase, which may last years; the accelerated phase, which may last months; and blast crisis, which is treated more like acute myelogenous leukemia (AML).
Treatment for CML in the chronic phase and accelerated phase may include a classification of drugs called tyrosine kinase inhibitors (such as imatinib mesylate, commonly known as Gleevec?). Research indicates that these drugs are well tolerated and demonstrate prolonged responses.
At present, the only documented cure for CML is bone marrow transplant. The question about whether to do a bone marrow transplant will depend upon the health and age of the patient and whether a suitable bone marrow donor is present and how well the leukemia is responding to therapy.
The other consideration regarding bone marrow transplant is when it should be done – weighing risks versus benefits. As more is learned about the long-term responses to tyrosine kinase inhibitors, the role of bone marrow transplant will continue to be evaluated.
Chronic lymphocytic leukemia (CLL)
Chronic lymphocytic leukemia generally occurs in older adults and progresses slowly. People generally have no or few symptoms and since CLL is not curable, it is usually treated conservatively. CLL is the one type of leukemia that has a formal staging system.
Early disease (RAI Stages 0-I) consists of elevated lymphocytes and enlarged lymph nodes. Intermediate stage disease (RAI Stage II) includes an enlarged spleen. Advanced disease (RAI Stage III and IV) includes disturbed bone marrow function and significant decreases in the red blood cells and platelets.
Treatment in early stage disease may include observation, as most patients will live 10-15 years without treatment and earlier treatment does not appear to increase survival. Treatment usually begins in stage II if the patient has symptoms or in advanced disease. Treatment usually includes chemotherapy most people will respond well to therapy.
Hairy cell leukemia
Hairy cell leukemia is a rare type of chronic leukemia in which the leukemia cells appear to have hair when examined under the microscope. About 85 percent of people with hairy cell leukemia will respond very well to the chemotherapy. Many remissions will last longer than 10 years and treatment can be repeated.