Radiotherapy: an update

Radiotherapy is defined as the treatment of malignant (occasionally non malignant) diseases by ionizing radiation. Radiation oncology is the science that deals with the study of tumor biology and application of ionizing radiation in the management of cancers. It is based on the principle that rapidly proliferating cells are more sensitive to ionizing radiation compared to normal cells. This differential cell kill is used for the treatment of tumors. A dose of radiation that is sufficient to kill cancer cells will produce considerable if not permanent damage to the normal tissues. The malignant cells which have a high rate of mitosis are highly susceptible to the action of radiation. However, the normal cells recover but not the malignant tissues. Thus the aim of radiotherapy is to deliver a homogenous dose of radiation to an accurately localized tissue target volume in order to produce tumor control with minimal effect on the surrounding normal structures