Donor Stem Cell Transplant in Treating Older or Frail Patients With Hematologic Cancer

OBJECTIVES: Primary * Determine the safety of non-myeloablative allogeneic peripheral blood stem cell transplantation, in terms of regimen-related organ toxicity and toxicity from acute graft-vs-host disease (GVHD), in older or medically frail patients with high-risk indolent hematologic malignancies. * Determine overall survival, disease-free survival, and relapse risk at 1, 2, and 3 years post-transplantation in these patients. Secondary * Determine the engraftment of donor hematopoiesis at 6 weeks, 3 and 6 months, and 1 year post-transplantation in these patients. * Determine the incidence and severity of chronic GVHD in older and medically infirm patients treated with this regimen. * Determine the safety and efficacy of collecting peripheral blood stem cells from older donors (age \> 60 years). * Determine the need and efficacy of donor lymphocyte infusions in patients with residual disease after transplant. OUTLINE: * Non-myeloablative preparative regimen:Patients receive fludarabine IV over 30 minutes on days -7 to -3, busulfan IV over 2 hours every 8 hours on days -4 and -3, and anti-thymocyte globulin IV over 8 hours on days -4 to -1. * Transplantation: Patients undergo allogeneic peripheral blood stem cell transplantation on day 0. Patients receive filgrastim (G-CSF) subcutaneously beginning on day 6 and continuing until blood counts recover. * Graft-vs-host disease (GVHD) prophylaxis: Patients receive tacrolimus orally every 12 hours or IV continuously beginning on day -2 and continuing until day 90, followed by a taper until day 180. Patients also receive methotrexate IV over 15-30 minutes on days 1, 3, 6, and 11. * Donor lymphocyte infusions (DLIs): Patients with residual disease ≥ 6 months post-transplantation who are off immunosuppression for ≥ 30 days with no evidence of GVHD may receive DLIs. DLIs are administered ≥ 12 weeks apart in the presence of persistent disease, absence of severe (grade 3-4) GVHD, and absence of persistent GVHD after the first DLI. After completion of study therapy, patients are followed periodically for 5 years. PROJECTED ACCRUAL: A total of 30 patients will be accrued for this study.