放射治疗是恶性肿瘤综合治疗的重要组成部分，电离辐射通过直接电离和活性氧分子间接作用导致肿瘤细胞DNA发生损伤，进而引起细胞死亡。在临床中，放疗在不同患者之间治疗效果存在明显差异，即放射敏感性差异。已有研究认为放射敏感性主要与DNA损伤识别和修复过程中的关键蛋白成分结构和功能密切相关，然而早前研究多集中于患者的生殖系基因组单细胞核苷酸多态性与放射敏感性之间的关系，忽略了肿瘤自身所发生的体细胞突变的影响。根据最近的胃癌肿瘤基因组研究，在肿瘤中DNA修复相关基因同样也会发生很多体细胞突变。因此我们推测这些DNA修复相关基因的突变同样也可能影响肿瘤的放疗效果。由此，本研究将采用靶基因捕获测序技术，对250名放疗的胃癌患者的肿瘤组织进行DNA修复相关基因的体细胞突变筛查，结合临床数据和疗效，评估DNA修复基因体细胞突变对放疗效果的影响，进而为临床治疗手段的选择提供科学依据和策略。

Radiotherapy is an important component of multidisciplinary treatment for malignant tumor, radiation can cause DAN damage to cancer cells by direct ionization and the indirect interaction of produced reactive oxygen, which leads to cell death. While respond to radiotherapy varies among patients because of different radiosensitivity. It is reported that constitutions and function of the key proteins in the DNA damage sensor and repair process is closely related with radiosensitivity, and most of researchers focus on the relationship between the patients Germline genome single nucleotide polymorphisms and radiosensitivity, while not the influence of tumor cells’ somatic mutations. According to the recent gastric genomics study, there are also many somatic mutations in the DNA repair related genes. Therefore, we speculate that these mutated genes could influence the tumor radiotherapy effect. This project will screen the DNA repair genes somatic mutation status in 250 gastric patients who received radiotherapy using target sequencing, then combine with the clinic characteristics and treatment effect, evaluate the influence of DNA repair genes mutations on radiotherapy, further to provide theory and scientific strategy for the choice of clinical treatment.