Reduced Intensity Donor Stem Cell Transplant in Treating Patients With High Risk Acute Lymphocytic Leukemia in Complete Remission

PRIMARY OBJECTIVES: I. To determine if a one-year disease-free survival (DFS) of \> 25% can be achieved among adult patients with high risk acute lymphocytic leukemia (ALL) in complete remission (CR) who undergo nonmyeloablative allografting. II. To determine if a one-year DFS of \>= 40% can be achieved among pediatric patients with high risk ALL in CR who undergo nonmyeloablative allografting. SECONDARY OBJECTIVES: I. To determine if a day +200 transplant-related mortality (TRM) of \< 25% can be achieved among patients with high risk ALL in CR who undergo nonmyeloablative allografting. II. To evaluate the efficacy and toxicity of donor lymphocyte infusion (DLI) in the treatment of minimal residue disease (MRD) after nonmyeloablative allografting for patients with high risk ALL in CR. OUTLINE: NONMYELOALATIVE CONDITIONING REGIMEN: Patients receive fludarabine phosphate intravenously (IV) on days -4 to -2 and undergo total body irradiation (TBI) on day 0. TRANSPLANTATION: Patients undergo allogeneic peripheral blood stem cell transplantation (PBSCT) on day 0. Patients with minimal residual disease may receive donor lymphocyte infusion IV. IMMUNOSUPPRESSION: Patients receive cyclosporine orally (PO) every 12 hours on days -3 to 100 with taper to day 177 and mycophenolate mofetil PO very 8 hours on days 0 to 40 with taper to day 96. After completion of study treatment, patients are followed up at days 28, 56, 84, 120, 180, and 360; at 18 months; and annually for up to 5 years.