John D Norlund

Tumors are made up of cells that are reproducing at abnormally high rates. Radiation therapy specifically acts against cells that are reproducing rapidly. Normal cells are programmed to stop reproducing (or dividing) when they come into contact with other cells. In the case of a tumor, this stop mechanism is missing, causing cells to continue to divide over and over. It is the DNA of the cell that makes it capable of reproducing. Radiation therapy uses high energy x-rays to damage the DNA of cells, thereby killing the cancer cells, or at least stopping them from reproducing.