Radiation Therapy
Radiation therapy, or radiotherapy, uses high-energy rays to damage or kill cancer cells and prevent them from growing and dividing, or to ease symptoms caused by cancer.
Similar to surgery, radiation therapy is typically a local (not systemic) treatment to eliminate or eradicate visible tumors. Radiation therapy is not typically useful in eradicating cancer cells that have already spread to other parts of the body.
Radiation therapy may be externally or internally delivered.
External radiation delivers high-energy rays directly to the tumor site from a machine outside the body.
Internal radiation, or brachytherapy , involves the placement of a small amount of radioactive material in or near the cancer.