Radiation therapy (also called radiotherapy) is a cancer treatment that uses high doses of radiation to kill cancer cells and shrink tumors. At low doses, radiation is used in x-rays to see inside your body, as with x-rays of your teeth or broken bones.

BENEFITS

To cure or shrink early-stage cancer Some cancers are very sensitive to radiation. Radiation may be used by itself in these cases to make the cancer shrink or completely go away. In some cases, chemotherapy or other anti-cancer drugs may be given first. For other cancers, radiation may be used before surgery to shrink the tumor (this is called pre-operative therapy or neoadjuvant therapy), or after surgery to help keep the cancer from coming back

To stop cancer from coming back (recurring) somewhere else Cancer can spread from where it started to other body parts. Doctors often assume that a few cancer cells might already have spread even when they can’t be seen on imaging scans like CT scans or MRIs.

To treat symptoms caused by advanced cancer Sometimes cancer has spread too much to be cured. But some of these tumors can still be treated to make them smaller so that the person can feel better. Radiation might help relieve problems like pain, trouble swallowing or breathing, or bowel blockages that can be caused by advanced cancer. This is called palliative radiation.

To treat cancer that has returned (recurred) If a person's cancer has returned (recurred), radiation might be used to treat the cancer or to treat symptoms caused by advanced cancer. Whether radiation will be used after recurrence depends on many factors. For instance, if the cancer has come back in a part of the body that has already been treated with radiation, it might not be possible to give more radiation in the same place. It depends on the amount of radiation that was used before. In other instances, radiation might be used in the same area of the body or a different area. Some tumors do not respond as well to radiation, so radiation might not be used even if they recur.