Extracorporeal means "outside the body." Irradiation or radiation is a treatment for cancer. When something is radiated outside the body, it is called extracorporeal irradiation.

You may wonder how something in the body can be radiated outside the body. This can be done, for example, when a piece of cancerous bone is removed. Radiation is then applied to the bone before returning it to the body. This method is used only occasionally and usually in places where donor bone is not available.