Leukemia and lymphomas are cancers that leave our bodies vulnerable to attack from without or within.
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The blood and lymphatic system play key roles in defending the body from attack by infectious agents. Leukemia and lymphomas are cancers that sometimes develop in these defensive areas, leaving our bodies vulnerable to attack from outside as well as from within our own blood and lymph systems. New drugs and treatment methods are turning the tide in the battle against these difficult targets.
Leukemia is a cancer of the blood cells. In the past a diagnosis of leukemia left little room for hope. Today, significant advances in treatment have seen five-year survival rates soar from only 14 percent in 1960 to 44 percent today. And for children with acute lymphocytic leukemia (ALL), survival rates are as high as 80 percent.
There were 30,000 new cases of leukemia in the United States in 2001. It can occur at any age. Some types are more likely to affect children, but more than half of all cases occur in adults over age 60. There is no single cause, but risk factors include previous cancer therapy, certain genetic disorders and exposure to intense radiation or to some chemicals.
Leukemia includes a number of types of blood cancer, but most involve an excess production of cancerous white blood cells.
Blood is made up of oxygen-carrying red blood cells, infection-fighting white blood cells, and platelets that help blood clot, all suspended in plasma. When too many defective white blood cells are produced, they crowd out both healthy white cells and red cells.
Leukemia is usually described according to the type of white blood cell affected and by the speed of cell growth, either acute or chronic. There are four main types:
Acute lymphocytic leukemia (ALL). This occurs when white lymphoid cells proliferate. It is the most common cancer in children and is responsible for a little over half the cases of childhood leukemia.
Acute myelogenous leukemia (AML). This type affects both children and adults and progresses rapidly. It accounts for a little less than half of childhood leukemias.
Chronic lymphocytic leukemia (CLL). Seen almost exclusively in adults it is the most common adult leukemia. It progresses slowly.
Chronic myelogenous leukemia (CML) affects adults, is also slow growing but is less common than CLL.
Symptoms of leukemia can include flu-like symptoms, tiredness, fever, weight loss, a tendency to bruise or bleed, night sweats, enlarged lymph nodes and vulnerability to infection. Some people have no noticeable signs. Diagnosis requires blood tests followed by a bone marrow test.
All types of leukemia can be treated. Chemotherapy is used to treat most cases. Radiation therapy may also be used in addition to chemotherapy.
When patients don’t respond or relapse after a period of remission, either bone marrow transplants or stem cell or umbilical cord blood transplants may offer patients the best hope of survival.
Immunotherapy, also known as biological therapy, may be used to stimulate the body’s immune system to fight cancer and to repair the body during treatment.
A new drug, Gleevec (imatinib mesylate) represents a new approach to treating leukemia and has shown promise in trials to date. Gleevec works by blocking the growth of white blood cells. Early trials showed it greatly reduced the level of cancerous cells in the bone marrow and blood of patients with CML. It also has the advantage of being an oral drug with a high response rate and an acceptable level of side effects.
New drugs and treatment methods are turning the tide in the battle against these cancers of the blood and lymph system.
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When the Lymph Is Attacked
Lymphomas are cancers that develop in the lymph system, a network of vessels that carry lymph fluid throughout the body. Lymph fluid contains white blood cells charged with fighting infection.
There are two main types of lymphomas: Hodgkin’s disease, which is less common and has been on the decline in recent years; and non-Hodgkin’s lymphoma, a form that is becoming more common, the incidence having doubled since the 1970s.
Monoclonal antibodies, stem cells, umbilical cord blood transplants and new drugs offer patients increased hope.
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Hodgkin’s disease is most often seen in men in their 20s and 60s. There is a link with it and Epstein-Barr virus.
Non-Hodgkin’s lymphoma is diagnosed in 54,000 Americans annually, making it the sixth most common form of cancer. An estimated 24,000 persons die from the disease annually. It is characterized by uncontrolled growth of lymphocytes (white blood cells) in the lymphatic system.
Risk factors for non-Hodgkin’s lymphoma include a weakened immune system (persons who take immunosuppressive drugs or persons with HIV/AIDS); infection with certain viruses (Epstein Barr virus and Human T-cell leukemia/lymphoma virus, known as HTLV-1); and environmental exposure to certain chemicals including pesticides, solvents and fertilizers. Farmers have a high rate of non-Hodgkin’s lymphoma, probably because of their exposure to pesticides and fertilizers.
Treatment depends on the form the disease takes. With aggressive forms treatment needs to begin immediately. Long-term remission is possible for about half of these patients. Other patients have a more chronic form of lymphoma that may cycle through more active stages followed by remission over a number of years. Sometimes patients with the chronic form are watched carefully and treatment may not begin until the disease progresses.
Treatment options include chemotherapy, radiation therapy (often when it can be targeted to a specific area such as lymph nodes in the neck), bone marrow and stem cell transplants, and immunotherapy.
Immunotherapy uses monoclonal antibodies, man-made genetically engineered proteins that are designed to selectively target and destroy lymphoma cells, leaving healthy cells unharmed.
A recent European trial of 400 patients found that adding monoclonal antibody therapy using the drug rituximab to standard chemotherapy drugs improved survival in patients over age 60 with large B-cell lymphoma.
Of the patients receiving rituximab plus chemotherapy, 76 percent were in complete remission after one year with an overall survival rate of 83 percent. In the chemotherapy-only group 60 percent of patients were in complete remission and overall survival was 68 percent.
Further trials are currently underway in the United States. If the early promise shown by rituximab holds up, it will represent a major advance against large B-cell lymphoma, the most common type of non-Hodgkin’s lymphoma, accounting for about 17,000 new cases per year.
A further benefit of this new therapy is that it was very successful in patients over age 60, a group that doesn’t respond well to chemotherapy.
Progress against both leukemias and lymphomas has been slow but steady in recent decades. Monoclonal antibodies, the use of stem cells and umbilical cord blood transplants as well as the continued development of new drugs for chemotherapy offer patients hope that survival rates will continue to improve in the future.
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