Allogeneic Stem Cell Transplants Effective for Long-Term Remission of CLL
According to results recently presented at the 43rd annual meeting of the American Society of Hematology, allogeneic stem cell transplantation (SCT) improves cancer-free survival compared to autologous SCT in patients with 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.
High-dose chemotherapy followed by SCT is an effective treatment for patients with CLL. 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. In an autologous transplant, stem cells are collected from the patient prior to high-dose treatment. Because SCT is associated with severe side effects, current research is exploring which type of SCT is more effective at producing long-term remissions in patients with CLL.
The International Project on CLL/Transplant of the European Bone Marrow Transplant Group reported registry data comparing allogeneic and autologous SCT for 178 patients with different stages of CLL. Forty-six patients had undergone allogeneic SCT and 124 had completed autologous SCT.
Autologous SCT produced complete remission (disappearance of cancer) in 87% of the patients, with only 6% dying due to treatment. Five years following transplant, 63% of patients were alive, however, almost 60% of patients experienced a cancer recurrence. Patients receiving autologous SCT as an early treatment for CLL appeared to survive longer than patients with cancer resistant to chemotherapy agents when undergoing autologous SCT. Allogeneic SCT produced complete remissions in 67% of the patients, but 31% died from treatment-related complications within three months of completing allogeneic SCT. Five years following treatment, 45% of those patients surviving treatment remained free of cancer.
Results from this European research suggest that allogeneic SCT may produce a cure in a significant portion of CLL patients, despite the high treatment-related mortality rate and autologous SCT appears to prolong survival over conventional treatments. Individuals with CLL may wish to speak with their physician regarding the risks and benefits of a SCT 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 #2013, Orlando, Florida, December 2001)
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