Cancer is a major public health problem worldwide and is the second leading cause of death in the United States. The most common causes of cancer death are cancers of the lung, prostate, and colorectum in men and the lung, breast, and colorectum in women. These 4 cancers ac- count for 45 percent of all cancer deaths, with one quarter due to lung cancer. It has previously been suggested that approximately 50 percent of all cancer patients receive radiation as a treatment. In Radio Therapy (RT), ionizing radiation (IR) is delivered to the tumor via an external beam. Exposure to IR causes damage to various cellular components, with the DNA being the most critical target, directly or indirectly via ionization of molecules within the cells, generating a cascade of free radicals.