After radiotherapy, carcinoembryonic antigen usually decreases due to tumor killing, but the increase is abnormal, which may be caused by tumor progression due to insensitivity to radiotherapy, and the cause should be confirmed by relevant examinations. If carcinoembryonic antigen is still increased after radiotherapy, the first situation is that the tumor cells have poor sensitivity to radiotherapy, which leads to the disease still continues to progress, and then the patient may need to change to other treatments, such as chemotherapy, targeted drugs or immune drugs, etc., and the drugs need to be used under the guidance of the doctor. In case of elevated carcinoembryonic antigen in radiotherapy, it is necessary to consult the doctor in time, complete the relevant examination, and clarify the cause under the guidance of the doctor, so as to guide the next step of treatment.