Radiation therapy (also called radiotherapy) is the use of high-energy rays to damage cancer cells and stop them from growing. Like surgery, radiation therapy is local therapy; it can affect cancer only in the treated area. Radiation is sometimes used before surgery to shrink a tumor so that it is easier to remove. More often, radiation therapy is given after surgery to destroy any cancer cells that may remain in the area. It may also be given to relieve pain or other problems in patients whose tumors cannot be surgically removed. Radiation therapy is usually given on an outpatient basis in a hospital or clinic five days a week for several weeks.

Researchers are conducting clinical trials to look for more effective ways of using radiation therapy. For example, some are studying the benefits of using radiation both before and after surgery ("sandwich" technique), and others are giving radiation during surgery (intraoperative radiation). Doctors are also exploring the use of radiation therapy alone (instead of surgery) for rectal cancer that has not spread.

Here are some questions you may want to ask your doctor before receiving radiation therapy:

    * How will the radiation be given?
    * What is the goal of this treatment?
    * When will the treatment begin? When will it end?
    * What can I do to take care of myself during treatment?