Pathogenesis of side effects of radiation therapy in normal tissues

Abstract

The key challenge in radiotherapy is to select the appropriate maximum doses of radiation reaching the cancer cells while minimizing the damage to healthy tissue. The success of radiotherapy in the treatment of tumor depends mainly on the total dose administered during treatment whereas the tolerance to radiation of normal tissues is a certain limitation in the selection of maximum doses. In order to avoid any adverse effects after radiotherapy, certain dose thresholds should not be exceeded. The risk of radiation damage to normal tissues increases with the total dose, the number of radiotherapy fractions and the volume of tissues that have been irradiated. Patients under 10 years of age and patients over 70 are particularly susceptible to complications.

            Radiation used in radiotherapy causes damage to cellular structures responsible for basic cellular processes. X-rays collide with electrons causing ionization of molecules. These electrons lose the ability to function properly within the cell. In the course of this process, deoxyribonucleic acid (DNA - deoxyribonucleic acid) is damaged, which can cause mutations. The most susceptible to radiation damage are hematopoietic cells, endothelial cells, mucous membranes and the gastrointestinal tract. Thus, several effects can be distinguished following the contact of a living cell with ionizing radiation. The first of them can be such a big damage to the cell that it may be able to perform its functions and may be killed. The cell may also lose its ability to reproduce, although it may remain alive. The DNA code might be damaged so much that the resulting cell copies would be significantly different from the original cell. Radiation may also not cause side effects or maid have not effect on the cell at all.