**Abstract**

Although radiation therapy (RT) planning and execution techniques have evolved to minimize radiotoxicity to a considerable extent, adjacent tissues still receive a substantial dose of ionizing radiation, resulting in radiotoxicities that may limit patients' quality of life. Depending on the location of tissue injury and the severity of the cellular response, there may also be a need to interrupt RT, thus interfering with the prognosis of the disease. There is a hypothesis that genetic factors may be associated with individual radiosensitivity. Recent studies have shown that genetic susceptibility accounts for approximately 80% of the differences in toxicity. The evolution of genomic sequencing techniques has enabled the study of radiogenomics, which is emerging as a fertile field to evaluate the role of genetic biomarkers. Radiogenomics focuses on the analysis of genetic variations and radiation responses, including tumor responses to RT and susceptibility to toxicity in adjacent tissues. Several studies involving polymorphisms have been conducted to assess the ability to predict RT-related acute and chronic skin toxicities, particularly in patients with breast and head and neck cancers. The purpose of this chapter is to discuss how radiogenomics can help in the management of radiotoxicities, particularly radiodermatitis.

**Keywords:** neoplasms, radiation therapy, radiodermatitis, radiation genomics, single-nucleotide polymorphism
