Umbilical Cord Blood Transplant for Children With Lymphoid Hematological Malignancies

The purpose of this study is to determine the safety and effectiveness of UCBT to treat patients with lymphoid hematological diseases and to see if this treatment can decrease the incidence of leukemia relapse, GVHD and infections. These patients have a type of blood cell disorder that is very hard to cure. This treatment that is being used in this trial is known as a stem cell transplant. This treatment might help the patient live longer without the disease. It uses much stronger doses of drugs and radiation to kill the diseased cells that could be given without the transplant. We also think that the healthy cells from the donor may help fight any diseased cells left after the transplant. For the transplant to take place, we will administer stem cells from a 'donor' whose cells best 'match' the patient's. In this study umbilical cords will be the source of the stem cells. Before the transplant, two very strong drugs plus total body irradiation will be given to as preconditioning. This treatment will kill most of your blood-forming cells in the bone marrow. The patient will then get then healthy stem cells. If the patient has the disease in the central nervous system (CNS), they will receive radiation to the head and spine before starting the conditioning. This is to try to get disease control in the CNS. Radiation will not be given for children under 2 yrs old. Currently, many umbilical cord blood units are available in public banks for transplantation in patients lacking bone marrow donors. UCB transplants (UCBT) may offer several advantages over adult bone marrow or peripheral blood stem cell transplants, including: 1. rapid availability, 2. absence of donor risk, 3. low risk of transmissible infectious diseases, 4. low risk of acute GvHD (Graft vs. Host Disease) The three main causes of death after umbilical cord blood transplantation for these kind of disorders are graft failure, infection and disease relapse. In this study we are trying to address these three problems: To help improve engraftment we will add the drug Fludarabine to Cytoxan and total body irradiation. Fludarabine is a very strong medicine. We will try to decrease infections and reduce leukemia relapse by using fludarabine instead of antithymocyte globulin (ATG).