Radiation Therapy

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?
Radiation therapy is administered through several different methods:

• External radiation treatment refers to treatment to an area of the body by exposing it to a beam of x-rays or gamma rays. The rays penetrate the body from the outside, and deposit energy in the tissues in its path. The rays cause injury to all cells -- the normal, as well as the cancerous. Some are killed, some are injured and repair themselves, and some are not affected. Normal cells are injured, but are often able to repair themselves better than cancer cells.

• Radiation therapy is also administered by radiation implants. (Other terms for this include intra-cavitary implant, interstitial implant, radium implant, cesium implant, high dose rate insertion, needle implant, and others. The overall term is brachytherapy which means "slow therapy.")

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.