Radiation therapy

Radiation therapy — also called radiotherapy or X-ray therapy — involves treating cancer with beams of high-energy particles, or waves (radiation), such as gamma rays or X-rays. Although radiation can affect healthy cells as well as cancer cells, it's much more harmful to cancer cells because cancer cells divide more rapidly than most healthy cells do. Cells are more vulnerable to damage when they're dividing, making cancer cells more susceptible to radiation than normal cells are. In addition, normal cells can recover from the effects of radiation more easily than cancer cells can.
Many people with cancer undergo some type of radiation therapy. Your doctor may suggest using radiation therapy at different times during your cancer treatment and for different reasons, such as before surgery to shrink a cancerous tumor or after surgery to stop the growth of any remaining cancer cells. In addition, doctors sometimes use radiation therapy to shrink tumors to decrease the pressure, pain or other symptoms they may cause.

Chemotherapy

Chemotherapy uses medications to kill rapidly dividing cells. These cells include cancer cells, which continuously divide to form more cells, and healthy cells that divide quickly, such as those in your bone marrow, gastrointestinal tract, reproductive system and hair follicles. Healthy cells usually recover shortly after chemotherapy is complete — so, for example, your hair soon starts growing again.
Unlike radiation therapy, which treats only the part of your body exposed to the radiation, chemotherapy treats the body as a whole (systemically). Its purpose is to treat cells that may have escaped from where the cancer originated.
Depending on the type of cancer you have and whether it has spread, your doctor may use chemotherapy to:
Eliminate all cancer cells in your body, even when cancer is widespread
Prolong your life by controlling cancer growth and spread
Relieve symptoms and enhance your quality of life
In some cases, chemotherapy may be the only treatment you need. More often, doctors use it in conjunction with other treatments, such as surgery or radiation, to improve results.