Rituximab to the Preparative Regimen of Etoposide and Total Body Irradiation in Acute Lymphoblastic Leukemia

Primary Objective: * To determine the progression free survival (PFS) of the preparative regimen rituximab, etoposide and total body irradiation (TBI), in patients with acute lymphoblastic leukemia (ALL) receiving allogeneic hematopoietic stem cell transplantation (SCT). Secondary Objectives: * To determine the effect of rituximab on the incidence of acute graft vs. host disease (GVHD). * To determine the efficacy of adding imatinib mesylate post transplant in ALL patients with the t(9;22)(q34;q11) cytogenetic abnormality. * To estimate the probability of molecular complete remission at one year for the described treatment approach as determined by serial minimal residual disease (MRD) monitoring. * To determine the rate of GVHD, engraftment, toxicity, and overall survival (OS) for this treatment regimen.