External radiation (or external beam radiation): uses a machine that directs high-energy rays from outside the body into the tumor. Most people get external radiation therapy over many weeks. It’s done during outpatient visits to a hospital or treatment center.
Internal radiation: Internal radiation is also called brachytherapy. A radioactive source is put inside the body into or near the tumor.
Systemic radiation: Radioactive drugs given by mouth or put into a vein are used to treat certain types of cancer. These drugs then travel throughout the body.