Busulfan, Etoposide, and Total-Body Irradiation in Treating Patients Undergoing Donor Stem Cell or Bone Marrow Transplant for Advanced Hematologic Cancer

RATIONALE: Giving chemotherapy and total-body irradiation before a donor stem cell transplant or a donor bone marrow transplant helps stop the growth of cancer and abnormal cells and helps stop the patient's immune system from rejecting the donor's stem 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 mycophenolate mofetil and cyclosporine before and after transplant may stop this from happening. PURPOSE: This phase II trial is studying the side effects and best way to give busulfan together with etoposide and total-body irradiation and to see how well they work in treating patients who are undergoing a donor stem cell or bone marrow transplant for advanced hematologic cancer.