Bone is one of the most common metastatic sites of malignant tumors, and the incidence of bone metastases is higher than that of primary bone tumors, and most of them are multiple bone metastases. Both cancer and sarcoma can metastasize to the bone, among which bone metastasis caused by cancer is more common, accounting for about 80%~90%. The common tumors causing bone metastasis include breast cancer (65%~75%), prostate cancer (65%~75%), thyroid cancer (60%), bladder cancer (40%), lung cancer (30%~40%), kidney cancer (20%~25%) and malignant melanoma (14%~45%). The occurrence of bone metastasis indicates that the tumor has progressed to advanced stage, so the principles of treatment for bone metastases are to relieve pain, prevent and treat pathological fractures, improve the quality of life and prolong survival. The main purpose of surgical treatment is to treat and prevent pathological fracture, and the common methods include tumor removal, bone cement filling, internal fixation, external fixation, etc. Chemotherapy has therapeutic effect on both primary tumor lesions and metastatic lesions (including bone metastases), and its therapeutic effect depends on the sensitivity of tumor to chemotherapeutic drugs. Radiotherapy is mainly used for the treatment of single bone metastases to control the development of local lesions and reduce symptoms, and the efficiency of local pain control can reach over 70%. (a) Application of bisphosphonates: Bisphosphonates are the most commonly used drugs for the treatment of cancer bone metastases, and have become the first choice for the treatment and prevention of cancer bone metastases because of their precise efficacy and low side effects. Bisphosphonate drugs are divided into two types: nitrogen-free and nitrogen-containing. Nitrogen-free bisphosphonates are metabolized intracellularly to produce cytotoxic, non-hydrolyzed adenosine triphosphate analogs. Nitrogen-containing bisphosphonates inhibit protein modification, inhibit the formaldehyde valproate biosynthetic pathway, and inhibit osteoclast-mediated bone resorption. Nitrogen-containing bisphosphonate drugs have a more potent inhibitory effect on bone resorption. The mechanism of bisphosphonate drugs for the treatment of cancer bone metastases is mainly to inhibit hydroxyapatite dissolution, inhibit osteoclast activity, prevent bone resorption, relieve bone pain, and delay the occurrence of bone complications. Commonly used drugs include disodium hydroxymethyldiphosphonate (bone phosphonate), disodium pamidronate (Acodar), ibandronate (Eben) and zoledronic acid (Zetex). Although the activity of several generations of drugs varies greatly, the efficiency of treating bone metastases and relieving bone pain is relatively close, about 53%-70%. Zettai is a new generation of nitrogen-containing bisphosphonate drugs newly marketed in China in 2005, which is powerful and convenient to use and has better efficacy in osteolytic, osteogenic and mixed bone metastases caused by various tumors. Zoledronic acid has significant efficacy in relieving bone pain. The results of multi-event analysis showed that zoledronic acid was more effective than pamidronate disodium in treating bone metastases from breast cancer and could effectively delay the occurrence of skeletal-related events. There is no consensus on the duration of treatment with bisphosphonates for cancer bone metastases, and it is generally advocated to administer the drug once every 3-4 weeks, and then determine the duration of treatment according to the patient’s change in condition and affordability. The duration of treatment in foreign clinical studies reaches 21~24 months. The duration of treatment is longer when used to prevent bone metastasis. The situation in China is different, and the main influencing factor in actual clinical treatment is still the patient’s economic status, but it should be used at least twice in order to evaluate the efficacy. The main adverse effects of bisphosphonate therapy include fever, chills, nausea, vomiting, diarrhea, general malaise, and low blood calcium. They are usually mild and can be treated symptomatically. When applying bisphosphonate treatment, calcium and vitamin D should be used together, and the change of serum creatinine level should be checked, and the drug should be temporarily stopped if renal function is found to be reduced. (ii) Radionuclide therapy The principle is to use osteophilic radioactive substances for in vivo radiation therapy, so it is also called internal irradiation therapy. The commonly used drugs are 153Sm-EDTMP, 89Sr, 32P, etc. 153Sm is an early used internal irradiation nuclide, which mainly emits b-rays to kill tumor cells directly or indirectly (by ionizing radiation effect). 153Sm also emits g-rays for lesion review, EDTMP has strong affinity and high specificity for bone metastasis lesions and inhibits osteoclasts in bone tumor tissues. After injection of 153Sm-EDTMP, 60% concentrated in bone and less than 2% distributed in non-bone tissues. 153Sm has short half-life, larger dose can be given at one time, the efficacy appears early, but the maintenance effect time is also short, about 1~2 months repeat treatment, 5~6 times continuous treatment is a course of treatment, the efficiency of bone pain treatment is 60%~80%. The radionuclide strontium 89 is a relatively new and effective internal irradiation agent for bone tumors. 89Sr emits pure b-rays with an energy of 1.46 MeV and a half-life of 50.6 days. After injected into the body, more than 70% of the b-rays can be concentrated in bone, and the concentration in bone metastases is even higher, reaching more than three times of normal bone. 89Sr produces b-rays, which can reduce the pain by concentrating the irradiation on the lesion, causing the tumor to shrink and destroy, and the bone cortical tension to decrease; on the other hand, it can achieve pain relief by reducing the osteolytic effect and thus the production of pain-causing substances in the tumor. Compared with 153Sm-EDTMP, 89Sr emits pure b-rays, and the radiation dose is smaller, which has less inhibitory effect on the bone marrow and less impact on the surrounding personnel, making it easier to treat in the ward. 89Sr has a long physical half-life and a long effective action time in the body, up to 3~6 months, which can greatly reduce the number of times patients come to the hospital for treatment. However, the price of 89Sr treatment is also much higher than 153Sm-EDTMP. Zhang Bicheng et al. treated 49 patients with multiple bone metastases with Sr internal irradiation, and the total effective rate of bone pain relief was 77.6%, which could lead to significant improvement in patients’ quality of life, reduction of blood calcium and ALP, and no significant toxic side effects. In recent years, 188Re has been used for the treatment of cancer bone metastases and has become one of the hot spots in nuclear medicine research at home and abroad.188Re is a solution of sodium perrhenate ((Na188ReO4) obtained from the 188w-188Re generator in carrier-free form by drenching with physiological saline.188Re emits b-rays with an energy of 2.12 Mev and has a range of 3.5 Mev in It also emits g-rays with an energy of 155key, which is suitable for imaging and tracking the distribution changes in the tissue. The radiation effect of 188Re can cause direct damage to biological macromolecules leading to apoptosis on the one hand, and ionize water molecules and produce oxygen radicals such as hydrogen peroxide on the other hand, which can indirectly accelerate apoptosis. In the treatment of bone metastases, the most mature research is the 188Re-labeled 1-hydroxy-1-ethylene-1,1-diphosphonate (188Re-HEDP), which is an osteophilic diphosphonate compound that participates in the metabolism of bone salts, inhibits osteolysis, and concentrates in sites of high bone metabolism, especially in bone metastases. 188Re-HEDP is mainly excreted through the urinary system, and is found in the liver, thyroid and lung. 188Re is an ideal radionuclide for the treatment of bone metastases, and 188Re-HEDP has good physicochemical properties and biological characteristics. The quality of life of all patients in the 188Re treatment group was improved without significant myelosuppression, while 83% of patients in the 186Re and 89Sr treatment groups had varying degrees of improvement in quality of life, but a significant proportion of patients had decreased white blood cells and platelets. Sang Shibiao et al. reported that the total effective rate of pain relief in patients with bone metastases treated with 188Re-HEDP was 83.7%; the total effective rate of disappearance or shrinkage of bone metastases after treatment was 23.7%. The efficacy of radionuclide therapy can be produced 24~48 hours after the drug is administered and maintained for 1~6 months. The main adverse effect of radionuclide therapy is bone marrow suppression. Therefore, special attention should be paid to bone marrow suppression when applied in combination with chemotherapy and radiotherapy. In addition to the above mentioned drugs and methods, calcitonin, some Chinese herbal medicines such as Eleuthero milk and Addy injection also have certain efficacy on bone metastases. Symptoms, MRI, CT, and nuclear examination are all valuable when making the determination of efficacy. For osteolytic bone metastases, the reduction of the area of destruction of the lesion, the appearance of a sclerotic edge or thickening of the sclerotic edge around it, the reduction or decrease of the nuclear concentration area, and the decrease of the signal of MRI T2-weighted image all indicate that the treatment is effective. The treatment of tumor requires close collaboration of multiple disciplines, and the treatment of bone metastases is an important part of comprehensive tumor treatment, so it is not possible to apply only one method, nor should the treatment of the primary tumor and other parts of metastases be neglected while only paying attention to bone metastases. There are many methods to treat bone metastases, and it is more important that doctors should reasonably choose different treatment methods such as surgery, chemotherapy, radiotherapy, nuclear therapy, bisphosphonate drugs and pain medication according to the specific conditions of patients, so as to minimize the pain of patients, improve the quality of survival and prolong the survival period.