Radiation therapy uses high-energy rays or particles to destroy cancer cells or slow their rate of growth. The goal of radiation therapy may change based on the situation.

For some cancers that have not spread too far from their site of origin, it can be used alone or with other treatments such as surgery with the goal of trying to cure the cancer.

If cancer has spread extensively, radiation can be used to relieve symptoms such as pain, bleeding, trouble swallowing, blocking of the intestines, compression of blood vessels or nerves by tumors, and problems caused by metastases to bones.

External beam radiation therapy

The most common way to deliver radiation to a cancer is to carefully focus a beam of radiation from a machine outside the body. This is known as external beam radiation. To reduce the risk of side effects, doctors carefully figure out the exact dose and aim the beam as accurately as they can to hit the target.

External beam radiation therapy is much like getting a diagnostic x-ray, but the radiation is more intense. The procedure itself is painless. Each treatment lasts only a few minutes, although the setup time -- getting you into place for treatment -- usually takes longer. The radiation is usually divided into many treatments over several days or weeks.

Internal radiation therapy (brachytherapy)

Another method of delivering radiation is called internal radiation, interstitial radiation, or brachytherapy. Instead of using radiation beams aimed from a large machine, a radioactive material is placed directly into, or as close as possible to, the cancer. This type of radiation travels a very short distance in the body. The material itself may be left in the body for only a short time, or it may be left there permanently.

Internal radiation therapy allows your doctor to give a dose of radiation to a smaller area and in a shorter time than is possible with external radiation treatment.

Sometimes, both internal and external beam radiation therapies are used together.

Possible side effects of radiation therapy

Side effects can vary from patient to patient and depend on the radiation dose and the part of your body treated. Some of the possible side effects are listed below:

• Radiation therapy can generally cause fatigue (feeling tired) and loss of appetite.

• External beam radiation may cause skin changes like a sunburn or suntan and hair loss at the site where the beams enter the body.

• Radiation therapy to the head and neck area often causes damage to the throat and salivary glands, which can result in dry mouth, sore throat, mouth sores, hoarseness, trouble swallowing, loss of taste, and cavities in the teeth. It may also damage the thyroid gland, which may require pills to replace thyroid hormone.

• Radiation of the abdomen can cause nausea, diarrhea, vomiting, and temporary or permanent damage to the intestines.

• Chest radiation may cause lung scarring that can eventually lead to shortness of breath.

Chemotherapy may make some of the side effects of radiation worse. There are ways to relieve many of these side effects, so it is important to discuss these symptoms with your cancer care team.

For more information on radiation therapy, see our document, Understanding Radiation Therapy: A Guide for Patients and Families.

Last Medical Review: 10/15/2009
Last Revised: 10/15/2009