Radiation is considered a local treatment because only cells in and around the cancer are affected. It is not useful against cancer that has already spread to distant parts of the body, because most forms of radiation therapy do not reach all parts of the body. Radiation may be used in several ways.

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 disappear completely. For other cancers, it may be used before surgery (pre-operative therapy) to shrink the tumor, or after surgery to prevent the cancer from coming back (adjuvant therapy). It may also be used along with chemotherapy in some cases. When radiation is used along with other forms of therapy, the treatment is planned by the surgeon, medical oncologist, and radiation oncologist, as well as the patient.

To stop cancer from recurring (coming back) in another area

If a type of cancer is known to spread to a certain area, doctors often assume that a few cancer cells may have already spread there, even though imaging scans (such as CT or MRI scans) show no tumors. That area may be treated to keep these cells from growing into tumors. For example, people with some types of lung cancer may get preventive (or prophylactic) radiation to the head because this type of cancer often spreads to the brain.

To treat symptoms caused by advanced cancer

Some cancers may spread too far to be cured. But this does not mean they can't be treated to make the person feel better. Radiation may help to relieve symptoms such as pain, trouble swallowing or breathing, or bowel problems that can be caused by advanced cancer. This is often referred to as palliative radiation.

Go back to Radiation Principles.

Last Medical Review: 07/17/2009
Last Revised: 07/17/2009