For example, if only the whole breast is irradiated after breast-conserving surgery, the patient’s reaction to radiation therapy is usually skin reaction, and this skin reaction only appears slowly after 3-4 weeks of radiation therapy, and by the end of radiation therapy, the reaction to radiation therapy is still relatively mild and only manifests as pigmentation. Then there is hair follicle expansion and some of the skin in the radiotherapy area will be red, which is the reaction of radiotherapy after breast-conserving surgery. For patients who have undergone mastectomy, their radiotherapy reactions, too, start to appear at 3-4 weeks after radiotherapy. The skin reactions after radiotherapy may include hyperpigmentation, redness, erythema, radiopharyngitis, such as sore throat and obstructive feeling when eating, such reactions. In case of breast cancer, such as brain metastasis, there may be dizziness and loss of appetite as the radiotherapy proceeds, and such reactions may occur. In general, the reaction to radiation therapy for breast cancer may vary depending on the site of radiation therapy.