The causes of bone pain after radiotherapy for breast cancer include radiotherapy side effects, osteoporosis, bone metastasis, etc. Generally, it is necessary to take medicines, radiotherapy and other treatments to reduce pain according to different causes. 1. The radiotherapy area of breast cancer is mostly the whole breast, which may cause the side effect of damage to the sternum in the radiotherapy area, and thus pain after treatment, but in recent years, with the development of radiotherapy technology, this side effect is less frequent in general. 2. Due to breast cancer and endocrine therapy, breast cancer patients are prone to osteoporosis complication, and thus are prone to the symptom of pain in many bones of the whole body. 3. Bone metastasis of breast cancer will usually cause bone pain and fracture.