Contraindications to radiotherapy include absolute contraindications and relative contraindications. Absolute contraindications mainly include malignant disease, etc. Relative contraindications mainly include tumors that are insensitive to radiation, tumors that are heavily sensitive to radiotherapy combined with distant metastases, etc. Radiotherapy is a kind of local treatment method using radiation to treat tumors. Absolute contraindications to radiotherapy are mainly for advanced cancer patients with obvious malignant disease, such as poor nutritional status, who cannot bear radiotherapy treatment. In addition, perforated esophageal cancer, large amount of fluid in the lumen, large amount of carcinomatous pleural fluid in lung cancer, large amount of ascites in liver cancer, etc. should be regarded as contraindications to radiotherapy. Relative contraindications to radiotherapy mainly include radiation-insensitive tumors such as soft tissue sarcoma and moderately sensitive tumors with distant multiple metastases. In addition, radiotherapy should be done after controlling the disease when the tumor is combined with other serious diseases, and radiotherapy should be considered after the blood picture is normalized when the white blood cells in the peripheral blood are lower than 4×10⁶/liter or platelets are lower than 80×10⁶/liter. For cancer patients, it is recommended to go to regular hospitals and have treatment plans formulated by specialists in combination with the patients’ examination results and physical conditions, and the patients should not diagnose and treat on their own in order to avoid delaying their conditions.