How Radiation Therapy Works

Radiation therapy is used to:

Treat cancer

Radiation can be used to cure cancer, to prevent it from returning, or to stop or slow its growth.

Ease cancer symptoms

Radiation may be used to shrink a tumor to treat pain and other problems caused by the tumor. Or, it can lessen problems that may be caused by a growing tumor, such as trouble breathing or loss of bowel and bladder control.

Radiation therapy does not kill cancer cells right away. It takes days or weeks of treatment before cancer cells start to die. Then, cancer cells keep dying for weeks or months after radiation therapy ends.

Radiation may be given before, during, or after surgery. Doctors may use radiation

  • Before surgery, to shrink the size of the cancer.
  • During surgery, so that it goes straight to the cancer without passing through the skin. Radiation therapy used this way is called intraoperative radiation.
  • After surgery, to kill any cancer cells that may remain.

Radiation may also be given before, during, or after other cancer treatments to shrink the cancer or to kill any cancer cells that might remain.