The implantation of radioactive seeds directly into a tumor.

A type of radiation therapy in which radioactive material sealed in needles, seeds, wires, or catheters is placed directly into or near a tumor. Also called implant radiation therapy, internal radiation therapy, and radiation brachytherapy.
Brachytherapy uses radiation to destroy cancer cells and shrink tumors. The radiation source, which looks like seeds, ribbons, or wires, is put into the body by using a catheter placed in or near the cancer cells. Sometimes an applicator or a balloon attached to a thin tube is used. Depending on the type of implant, the radiation source may be permanent, or stay in place for minutes, hours, or days.