RATIONALE: Radiation therapy uses high-energy x-rays to damage tumor cells. Bone marrow transplantation may be able to replace immune cells that have been destroyed by radiation therapy used to kill tumor cells. Sometimes the transplanted cells can make an immune response against the body's normal tissues. Mycophenolate mofetil and tacrolimus may be an effective treatment for graft-versus-host disease caused by bone marrow transplantation.