How Does Radiation Therapy Work?
Radiation therapy works primarily by damaging the genetic material (DNA) within cancer cells and limiting their ability to successfully reproduce.
Cancer cells whose DNA is damaged beyond repair stop dividing or die. When the damaged cells die, they are broken down and eliminated by the body’s natural processes. Normal cells are also affected by radiation, but they are able to repair themselves more effectively than cancer cells. In addition, your radiation oncologist will develop a plan to deliver the radiation to the tumor area, shielding as much surrounding normal tissue as possible, which also helps to reduce the radiation dose to the normal tissues. As the side effects of radiation therapy are due to the radiation dose delivered to the normal tissues, anything that can reduce that dose, reduces the potential side effects.
Radiation does not always kill cancer cells or normal cells right away. It might take days or even weeks of treatment for cells to start dying, and they may keep dying off for several weeks after treatment ends. Fast growing cancers and tissues that grow quickly, such as skin, bone marrow, and the lining of the intestines are often affected right away. In contrast, slow growing tumors or tissues that grow slowly such as nerve, breast, brain, and bone tissue may not show an effect from the radiation often until the treatment is complete. For this reason, radiation treatment can have long-term side effects that might not be seen until long after treatment is over.