Fludarabine Phosphate and Total-Body Irradiation Before Donor Peripheral Blood Stem Cell Transplant in Treating Patients With Chronic Lymphocytic Leukemia or Small Lymphocytic Leukemia

PRIMARY OBJECTIVES: I. To determine whether nonmyeloablative allogeneic hematopoietic stem cell transplantation (HSCT) from matched-related donors can improve the probability of survival 18 months after treatment for fludarabine (fludarabine phosphate)-refractory, fludarabine phosphate, cyclophosphamide, and rituximab (FCR)-failed, or del 17p chronic lymphocytic leukemia (CLL) beyond that observed in historical controls (30%). SECONDARY OBJECTIVES: I. To assess the rate of relapse with allogeneic HSCT using nonmyeloablative conditioning for patients with fludarabine-refractory, FCR-failed, or del 17p CLL compared with historical data on autologous HSCT. II. To estimate the incidence of grade 2-4 acute graft-versus-host disease (GVHD) and chronic GVHD in patients with CLL treated with low-dose TBI, fludarabine, peripheral blood stem cell (PBSC) infusion and immunosuppression with cyclosporine and mycophenolate mofetil. III. To characterize the rate and types of infections with this regimen. IV. To estimate the rate of transplant-related mortality in the first 200 days. OUTLINE: NONMYELOABLATIVE CONDITIONING: Patients receive fludarabine phosphate intravenously (IV) on days -4 to -2 and TBI on day 0. TRANSPLANT: Patients undergo allogeneic peripheral blood stem cell transplant on day 0. GVHD PROPHYLAXIS: Patients receive cyclosporine orally (PO) every 12 hours on days -3 to 180 with taper beginning on day 56 and mycophenolate mofetil PO every 12 hours on days 0-27. After completion of study treatment, patients are followed up at 12 and 18 months and then annually for 5 years.