Total-Body Irradiation and Cyclophosphamide in Treating Patients Who Are Undergoing Donor Stem Cell Transplant for Hematologic Cancer and Other Diseases

OBJECTIVES: Primary * Evaluate the potential efficacy of targeting cyclophosphamide to a metabolic endpoint when given together with total-body irradiation, in terms of day 200 nonrelapse mortality, in patients with hematologic cancer and other diseases who are undergoing allogeneic hematopoietic stem cell transplantation. Secondary * Determine the overall survival of patients treated with this regimen. * Determine the rate of relapse in patients treated with this regimen. * Determine the occurrence of sinusoidal obstruction syndrome in patients treated with this regimen. * Determine the occurrence of acute renal failure in these patients. * Determine the occurrence of respiratory failure in these patients. OUTLINE: * Conditioning regimen: Patients undergo total-body irradiation twice daily on days -6 to -4. Patients also receive cyclophosphamide IV over 1 hour on day -3 and then IV at a metabolism-based dose\* on day -2. NOTE: \*Patients undergo frequent blood sampling after completion of the first cyclophosphamide infusion for pharmacokinetic studies in order to determine the dose for the second cyclophosphamide infusion. * Allogeneic stem cell transplantation: Patients undergo allogeneic bone marrow or peripheral blood stem cell transplantation on day 0. * Graft-versus-host disease (GVHD) prophylaxis: Patients receive GVHD prophylaxis as per the attending physician, including one of the following regimens: cyclosporine and methotrexate; tacrolimus and methotrexate; tacrolimus and mycophenolate mofetil; or sirolimus, tacrolimus, and methotrexate (as per the GVHD prophylaxis regimen chosen for each patient). After completion of study treatment, patients are followed periodically for at least 200 days. PROJECTED ACCRUAL: A total of 50 patients will be accrued for this study.