How Does Radiation Therapy Work?

Radiation in high doses destroys or slows the growth of cancer cells. As a result, radiation therapy is used to cure, stop or decrease the growth of cancer. Radiation can also be used to reduce some symptoms or shrink cancer tumors. Because cancer cells grow and divide more rapidly than normal calles around them, radiation therapy can successfully treat many kinds of cancer. Healthy cells are also affected by radiation. Electronic Brachytherapy (eBx®) uses a miniaturized X-ray tube to apply radiation directly to the tumor site, and therefore emits less radiation to healthy tissue and organs.

Radiation therapy is often used with other cancer treatments. Here are some examples:

  • Radiation therapy and surgery. Radiation may be given before, during or after surgery. Doctors may use radiation to shrink the size of the cancer before surgery, or they may use radiation after surgery to kill any cancer cells that remain. Sometimes, radiation therapy is given during surgery so that it can be delivered directly to the cancer site after the tumor is removed. This is called intraoperative radiation therapy (IORT).
  • Radiation therapy and chemotherapy. Radiation may be given before, during or after chemotherapy. Before or during chemotherapy, radiation therapy can shrink the cancer so that chemotherapy is more effective. After chemotherapy, radiation therapy can be used to kill any cancer cells that remain.


National Cancer Institute (Radiation Therapy for Cancer: Questions and Answers), accessed on October 9, 2009.


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