Radiation therapy uses high-energy radiation to kill cancer cells. It is usually not part of the main treatment for AML, but there are a few instances in which it may be used: A. When cancer spread outside of the bone marrow and blood, such as to the brain and spinal fluid, or to the testicles. B. Radiation to the whole body is often an important part of treatment before a stem cell transplant. C. It is used (rarely) to help shrink a tumor (myeloid sarcoma) if it is pressing on the trachea (windpipe) and causing breathing problems. D. Radiation can be used to reduce pain in an area of bone that is invaded by leukemia, if chemotherapy hasn’t helped.