Acute Lymphocytic Leukemia - Treatment After Relapse

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Investigational Drugs

Tyrosine kinase inhibitors. Tyrosine kinase is a growth-stimulating protein. Tyrosine kinase inhibitor drugs block the cell signals that trigger cancer growth. Several tyrosine kinase inhibitors, including imatinib (Gleevec) and dastinib (Sprycel), have recently been approved for treating Philadelphia chromosome-positive ALL. In 2006 clinical trials, Nilotinib (AMN-107) produced excellent results in patients with Philadelphia chromosome positive ALL who are resistant to imatinib.

Monoclonal antibodies (MAbs). Used alone or in combination with chemotherapy, MAbs target specific antigens on ALL blast cells. Although MAbs have been studied primarily in the treatment of B-cell non-Hodgkin's lymphoma, drugs demonstrating benefit in preliminary trials of ALL include anti-CD20 (rituximab) and anti-CD22 (epratuzumab). Alemtuzumab (MabCampath) is also showing promise in treating relapsed or refractory T-ALL. More studies are needed to determine the best MAb regimens in ALL.

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Transplantation Procedures for Acute Lymphocytic Leukemia

In order to administer high-dose chemotherapy for advanced cancer cases, stem cell transplantation procedures may be used. These procedures are based on removal and replacement of stem cells, which are produced in the bone marrow. Stem cells are the early forms for all blood cells in the body (including red, white, and immune cells). Cancer treatments harm growing cells as well as cancer cells, and so the healthy stem cells must be replaced by transplanting them from the donor into the patient.

Collecting the Stem Cells

Sources of Cells. Stem cells must first be collected either from:

• Bone marrow (bone marrow transplantation)
• Blood (peripheral blood stem cell transplantation). Evidence suggests that peripheral blood stem cell transplantation may be the superior approach. Studies report survival rates of 45% in bone marrow transplant patients compared to 65 - 70% in stem cell transplant patients, with benefits being significant in those with more severe disease.
• Fetal umbilical cord or placentas. This procedure uses donor cells but has a lower risk for immune system rejection of the cells than with a standard donor transplant. It takes longer to restore blood cells with this process, however, so at this time its use is limited to children and sometimes adults with low weight. (Some studies indicate success for adults with normal weights.)