Whether rectal cancer needs radiotherapy or not needs to be determined according to the specific situation of patients: 1. For patients with stage I rectal cancer, radical surgery can clinically achieve a relatively satisfactory survival, so radiotherapy can be disregarded; 2. For patients with stage II, III or even IV rectal cancer, who cannot undergo complete radical surgery, or corresponding risk factors will occur, radiotherapy can be considered, such as preoperative radiotherapy or preoperative simultaneous radiotherapy for some patients. or preoperative synchronous radiotherapy. This part of patients can be treated with preoperative radiotherapy and then surgery. Of course, some patients can also undergo surgery first, and then undergo postoperative radiotherapy or postoperative simultaneous radiotherapy. In this way, the local recurrence of the tumor can be reduced. Therefore, patients with stage II, III or IV rectal cancer can reduce the recurrence rate or improve the survival period through radiotherapy.