What is radiation therapy?
Radiation therapy is the use of radiation to injure or destroy cancer cells. High-energy rays, including x-rays or gamma rays may be used against the cells. Radiation is often used in specific sites in the body, such as the ovary or uterus, and is considered a local therapy -- affecting cancer cells only in the treated area of the body.
How is radiation therapy administered?
There are two ways to deliver radiation therapy. However, external radiation is the usual type that is used for treatment of breast cancer. Consider the following:
- external radiation (external beam therapy) - a treatment that precisely sends high levels of radiation directly to the cancer cells. The machine is controlled by the radiation therapist. Since radiation is used to kill cancer cells and to shrink tumors, special shields may be used to protect the tissue surrounding the treatment area. Radiation treatments are painless and usually last a few minutes.
- internal radiation (brachytherapy, implant radiation) - radiation is given inside the body as close to the cancer as possible. Substances that produce radiation, called radioisotopes, may be implanted directly into the breast tumor. Internal radiation involves giving a higher dose of radiation in a shorter time span than with external radiation. Internal radiation for breast cancer is currently being studied and is considered experimental.
- radiofrequency ablation (RFA) - new technology under study uses a special probe to deliver high-energy radio waves to destroy the tumor cells.
The implants are placed in the cancer itself, or right next to it, and are usually left in place for several hours or several days and then removed. The implant gives off radiation to the surrounding tissue while it is in place. The amount of radiation administered is determined by the tolerance of the normal tissues that are also irradiated. Eventually, the implants are either removed or they die out.
New delivery methods for radiation therapy are under investigation.