Radiotherapy differs from chemotherapy in that only one course of radiotherapy may be given to a site, but specific treatments vary. For example, after surgery, if there is no residual, a prophylactic dose of 25 doses of 5000 cGy is usually given. However, the dose of radical radiotherapy is slightly higher, usually 30-35 sessions of 6000-7000 cGy irradiation dose. In addition, the dose of palliative radiotherapy needs to be weighed against the pros and cons; if the patient tolerates it well, a slightly higher dose of up to 6000-7000 cGy is recommended, and if the patient tolerates it poorly, a lighter dose is likely to be chosen. Usually only one radiotherapy is given to a site, i.e. no second radiotherapy is allowed in the acute phase, so the target area is particularly important when radiotherapy is given, and the radiologist needs to weigh the pros and cons of the treatment. If the tumor or lymph node metastasis occurs again in or near the irradiation field, radiotherapy is not an option.