According to results recently presented at the 43rd annual meeting of the American Society of Hematology, allogeneic and autologous stem cell transplantation (SCT) appear to increase survival rates and reduce frequency of relapses in adults with ALL in first complete remission. These results also suggest that allogeneic SCT appears even more effective than autologous SCT.
ALL, also called acute lymphoblastic leukemia, is a cancer of the bone marrow and lymph system. The bone marrow produces early blood-forming cells, called stem cells, which grow and mature into the three blood cell types: white blood cells, which fight infection; red blood cells, which carry oxygen to tissue; and platelets, which help blood to clot. ALL is characterized by uncontrolled production of immature lymphocytes (white blood cells), of which there are two types: B and T cells. These immature lymphocytes never mature enough to perform their specific function of fighting infection. In addition, these rapidly dividing cells crowd out and suppress the formation of other important blood cells, such as red blood cells, platelets and other white blood cells. ALL is an aggressive cancer that must be treated aggressively for optimal chances of a cure.
Standard treatment for adults with ALL consists of remission induction, which is initial therapy utilized to induce a remission (disappearance of cancer) followed by consolidation therapy, which is therapy used during a complete remission to kill any cancer cells that may have remained following previous therapy. Maintenance therapy is sometimes given following consolidation therapy to help prevent relapse in patients whose cancer is in remission. Remission induction therapies, consolidation therapies and maintenance therapies most often consist of chemotherapy.
However, because standard consolidation/maintenance therapy has a high relapse rate, researchers are exploring the effects of high-dose chemotherapy followed by SCT instead of chemotherapy alone following remission induction. 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 bone marrow, stored and then infused into the patient following the high-dose therapy. In an allogeneic SCT, stem cells are collected from a related or unrelated donor. In autologous SCT, stem cells are collected from the patient. Because SCT may cause severe side effects and has high rates of mortality, there is reluctance among patients and physicians to use SCT unless scientific evidence suggests it is highly effective.
Recently, researchers conducted a clinical trial investigating the efficacy of allogeneic SCT and autologous SCT as post-induction treatment in adult patients with ALL in first complete remission. All patients received standard induction therapy followed by one course of consolidation chemotherapy. Forty-six patients fifty years of age or younger with an HLA-matched family donor underwent allogeneic SCT. Seventy-eight patients who were too old or who lacked a family donor underwent autologous SCT. No maintenance therapy was given. Patients were followed on average for 49 months.
At five years following treatment, relapse rates were 61% for patients treated with an autologous SCT, compared to only 20% for patients treated with an allogeneic SCT. Overall survival was approximately 40% for patients treated with an autologous SCT and 53% for patients treated with an allogeneic SCT.
The researchers conducting this clinical trial concluded that both allogeneic and autologous SCT appear to be effective post-induction treatments for patients with ALL; however, allogeneic SCT appears to produce significantly greater long-term survival for these patients. Individuals with ALL may wish to speak with their physician regarding the risks and benefits of allogeneic and autologous SCT or about participating in a clinical trial evaluating novel therapeutic approaches. Two sources of information regarding ongoing information on clinical trials include comprehensive, easy-to-use listing services provided by the National Cancer Institute (
Proceedings from the American Society of Hematology, abstract #3567, Orlando, Florida, December, 2001)