Millions of people all over the world saved by the correct use of radiotherapy (1) and about 50 percent of cancer patients have at least ones in their course of treatment (2). Radiation therapy involves exposure to normal tissues as well as the tumor tissue and can cause damage to the normal cells because of the high energy of the gamma and X-ray (1). All molecules in the cell including lipids, proteins, carbohydrates and nucleic acids have potential to receive damage by radiation. However, deoxyribonucleic acid (DNA) because of its function is the most important molecule in the cell which will be affected by ionizing radiation. Gamma and X-ray by direct and indirect mechanisms induce damage to DNA (3, 4).
Damaged DNA (if does not repair)
Damaged DNA (if does not repair)