Goals of radiation therapy

Radiation is considered a local treatment because only cells in and around the cancer are affected. It can’t cure 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 is used to treat cancer in several ways.

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 (as pre-operative therapy) to shrink the tumor, or after surgery to prevent the cancer from coming back (this is called 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.

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) 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.

Treat symptoms caused by advanced cancer

Some cancers may have spread too far to be cured. But even some of these tumors can still be treated to make them smaller so that the person can 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 called palliative radiation.