According to results recently presented at the 43rd annual meeting of the American Society of Hematology, an allogeneic bone marrow transplantation may produce long-term, cancer-free survival for patients with recurrent chronic lymphocytic leukemia.
Chronic lymphocytic leukemia (CLL) is a cancer involving the lymph (immune) system, which includes lymph nodes, blood and blood vessels found throughout the body, as well as the spleen, thymus and tonsils. This cancer is found in high quantities throughout circulating blood and in bone marrow (spongy material inside large bones that produces blood forming cells). CLL is characterized by the production of atypical lymphocytes. Lymphocytes are specialized immune cells, of which there are two types: B and T-cells. These cells are produced in the bone marrow and each has a very specific function in aiding the body to fight infection. The large majority of CLL cases involve mature B-lymphocytes that tend to live much longer than normal, accumulating in the blood, bone marrow, lymph nodes and spleen. This results in overcrowding of these areas, suppressing the formation and function of blood and immune cells that are normally present. Additionally, the cancerous lymphocytes themselves do not function normally, leading to a further decrease in the ability of the body to fight infection. CLL is considered a slow-growing or low-grade cancer.
There is no standard therapy for patients with CLL that continues to progress following initial treatment, but high-dose chemotherapy followed by stem cell transplantation is one treatment option for patients with this stage of disease. High-dose chemotherapy and/or radiation tend to be more effective at killing cancer cells than lower doses of therapy. However, the high doses also kill blood-forming cells (stem cells) that are produced in the bone marrow, leaving patients susceptible to infection, anemia and uncontrolled bleeding. In order to rescue low levels of blood cells caused by high-dose therapy, stem cells are collected from either blood or bone marrow, stored and then infused into the patient following the high-dose therapy. In an allogeneic transplant, stem cells are collected from a related or unrelated donor. Although high-dose therapy and stem cell transplantation may be very effective at producing a cure in some cancers, it is also associated with a high incidence of severe side effects, leaving some physicians and patients hesitant to utilize this treatment option.
Researchers in Vancouver and Toronto recently conducted a clinical trial examining the efficacy of allogeneic bone marrow transplantation (BMT) in 34 patients with recurrent CLL. Patients received one of two high-dose chemotherapy regimens, followed by allogeneic BMT. Over 3 years following therapy, the overall survival rate was 45.5%. Only 22% of patients have experienced a recurrence of their cancer. The incidence of acute and chronic graft-versus-host-disease (donor lymphocytes attacking cells in the recipient’s body) occurred in 50% and 80% of patients, respectively. Approximately 14 patients died from treatment and/or graft-versus-host disease.
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Results of Canadian research suggest that an allogeneic bone marrow transplant may produce long-term, cancer-free survival in patients with recurrent CLL. The use of stem cells instead of bone marrow in the future may reduce treatment-related mortality. Individuals with CLL may wish to speak with their physician regarding the risks and benefits of allogeneic BMT or about participating in a clinical trial. Two sources of information regarding ongoing clinical trials include comprehensive, easy-to-use listing services provided by the National Cancer Institute (cancer.gov) and www.eCancerTrials.com. eCancerTrials.com also provides personalized clinical trial searches on behalf of patients.
(Proceedings from the 43rd American Society of Hematology, abstract #1752, Orlando, Florida, December 2001)
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