If cancer develops after radiation therapy, it doesn't happen immediately. Leukemias, for example, usually take 5 to 9 years to develop after exposure to ionizing radiation. Other types of cancer, however, may take much longer. Ionizing radiation is a type of high-energy radiation that has enough power to damage DNA and cause cancer.
This includes radon, x-rays, gamma rays, and other forms of radiation. Low-energy, non-ionizing forms of radiation, such as visible light and cell phone energy, have not been found to cause cancer in people. The public often misunderstands the relationship between radiation and cancer. Many people believe that any amount of radiation can cause cancer.
This is not true; a very large amount of radiation is needed to cause cancer. It is not known how this occurs or how many tumors are caused by radiation damage. Ionizing radiation has enough energy to dislodge electrons from atoms. This includes radiation used to treat cancer, radiation used in some types of medical imaging, radiation from natural radon gas, and radiation released by nuclear weapons and power plants.
Examples of non-ionizing radiation include radio waves, light, microwave and radar. The associations between exposure to ionizing radiation and the development of cancer are mainly based on the LSS cohort of Japanese atomic bomb survivors, the largest human population ever exposed to high levels of ionizing radiation. This data has been used to estimate the risk of developing cancer after exposure to ionizing radiation.