To control the growth and spread of cancer. To eliminate microscopic metastasis. To improve quality of life by easing symptoms associated with advanced cancer, such as pain from bone metastasis. Radiation therapy may be used either alone or in combination with other treatments. If radiation is used as part of a multimodal therapy program, it may be administered before another treatment, afterward or at the same time.
Radiation therapy can attack cancer cells in two different ways.
The ionizing rays or particles damage some cells directly. However, it is more common for radiation to interact with water in the cell nucleus to form unstable oxygen radicals, which are a group of elements or atoms that are incapable of prolonged existence in a free state. The oxygen radicals damage the cell's DNA, causing the cell to die or lose its ability to divide. Normal cells are also affected by ionizing radiation, but they are usually better able to repair the DNA damage. Tissues with fast cell turnover, such as the bone marrow, the epithelial linings and the hair follicles, are more sensitive to radiation than other tissues, such as muscles, tendons and nerves.