If you are found to be eligible to take part in this study, you will be assigned to a dose level of radiation therapy based on when you join this study. Three (3) dose levels of radiation therapy will be tested. Three (3) participants will be enrolled at each dose level. The first group of participants will receive the lowest dose level. Each new group will be randomly assigned (as in the roll of dice) to one of the dose levels, and the assignment will also depend on how the previous participants have done. Participants will not be assigned to one of the higher 2 of the 3 dose levels unless the lower dose level is found to be tolerable. The first and second groups will receive 12 treatments and the third group will receive 14 treatments (Monday through Friday for about 2½ weeks). Your doctor will tell you how many treatments you will receive.