Radiation treatment will last between 2 and 2 1/2 hours and will be given on 1 day about 1 to 1 1/2 weeks after you had the simulation. You will have a device (similar to plastic wrap) placed around you that will hold you still during the treatment. You will be checked for level of pain and/or discomfort before starting each session of radiation, and you may take pain medications before starting each session. All participants will be treated with radiation therapy that is guided by the CT-on-Rails procedure. On the day of radiation, you will also receive a CT scan using CT-on-Rails in the same treatment room, immediately before the radiation treatment.