Radiotherapy refers to the killing of tumor cells by radiation, which is a kind of treatment method, including distant radiotherapy and brachytherapy, as follows: 1. distant radiotherapy: also called external radiotherapy, it refers to the use of gamma knife, radioactive knife, tommy knife, proton knife and other X-rays through extracorporeal gas pedals to irradiate tumors in the body, so as to break the double-stranded helix chain of tumor DNA at the same time and prevent tumor cells from reproducing and replicating to kill tumors; 2. brachytherapy: it refers to the placement of radiation source into the body or radiation source into the tumor, such as cervical cancer, nasopharyngeal cancer, esophageal cancer and other cavity tumors, which are treated by radiation source placement into the body.