- Radiation Therapy Principles
- How does radiation work to treat cancer?
- Types of radiation used to treat cancer
- Goals of radiation therapy
- Who gives radiation treatments?
- How is radiation given?
- External beam radiation
- Internal radiation therapy (brachytherapy)
- Safety for the patient and family
- Possible side effects of radiation therapy
- Side effects of radiation to specific areas
- Second cancers
- Other general health concerns
- What’s new in radiation therapy?
- To learn more
Goals of radiation therapy
Most types of radiation are considered local treatments because the radiation is aimed at a specific area of the body (where there is a tumor). Only cells in that area are affected. Most forms of radiation therapy cannot not reach all parts of the body and so may not be helpful in treating cancer that has spread to many distant areas.
Radiation is used to treat cancer 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. Sometimes, a few cycles of chemotherapy are given first. For other cancers, it may be used before surgery (as pre-operative or neoadjuvant therapy) to shrink the tumor, or after surgery to prevent the cancer from coming back (this is called adjuvant therapy).
In treating some types of cancer, radiation may also be used along with chemotherapy (chemo). This is because the chemo acts as a radiosensitizer, a drug that makes the cancer cells more sensitive to radiation. These drugs make the radiation work better. Some chemotherapy drugs already in use (such as 5-fluorouracil or 5-FU) are known to be radiosensitizers. The drawback of giving chemo and radiation together is that side effects tend to be worse.
In other types of cancer, it’s better to use radiation before or after chemo.
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) somewhere else
If a type of cancer is known to spread to a certain area, doctors often assume that a few cancer cells might already have 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. Sometimes, radiation to prevent future cancer can be given at the same time that radiation is given to treat existing cancer, especially if the prevention area is close to the tumor itself.
To treat symptoms caused by advanced cancer
Sometimes cancer spreads 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 might help relieve symptoms such as pain, trouble swallowing or breathing, or bowel blockages that can be caused by advanced cancer. This is often called palliative radiation.
Last Medical Review: 10/23/2013
Last Revised: 10/23/2013