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

RATIONALE: Giving total-body irradiation and chemotherapy, such as cyclophosphamide, before a donor stem cell transplant helps stop the patient's immune system from rejecting the donor's stem cells and helps stop the growth of cancer or abnormal cells. When the healthy stem cells from a donor are infused into the patient they may help the patient's bone marrow make stem cells, red blood cells, white blood cells, and platelets. Sometimes the transplanted cells from a donor can make an immune response against the body's normal cells. Giving immunosuppressive therapy before or after transplant may stop this from happening. PURPOSE: This phase II trial is studying how well giving total-body irradiation together with cyclophosphamide works in treating patients who are undergoing donor stem cell transplant for hematologic cancer and other diseases.