Unlike external beam therapy (EBT), in which high-energy X-ray beams are
directed at the tumor from outside the body, brachytherapy involves placing
radioactive seeds or pellets (about the size of a grain of rice) directly
inside or next to the tumor. After several weeks or months, the radioactivity
level diminishes. The inactive seeds remain in the body, with no lasting
effect on the patient. Brachytherapy is most commonly used in prostate
and breast cancer, but can be used to treat cancers throughout the body,
including those of the cervix, head, neck, gallbladder, uterus, lungs and eyes.