Busulfan, Etoposide, and Intensity-Modulated Radiation Therapy Followed By Donor Stem Cell Transplant in Treating Patients With Advanced Myeloid Cancer

RATIONALE: Giving chemotherapy drugs, such as busulfan and etoposide, and intensity-modulated radiation therapy before a donor stem cell transplant helps stop the growth of cancer cells. It also 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 intensity-modulated radiation therapy together with busulfan and etoposide before a transplant may stop this from happening. PURPOSE: This phase I/II trial is studying the side effects and best dose of intensity-modulated radiation therapy when given together with busulfan and etoposide followed by a donor stem cell transplant and to see how well it works in treating patients with advanced myeloid cancer.