Metastatic bone tumors are common lesions of the skeletal system. According to the literature, of the more than one million new tumor patients in the United States each year, 50% of them eventually develop bone metastases. The most common site of these metastases is the vertebral body, followed by the hip region (around the acetabulum, upper femur), femoral stem, upper humerus and humeral stem, and less commonly the knee, elbow and their distal ends. Common primary tumors involved include: breast, lung, kidney, prostate, rectal, stomach, colon, and ovarian cancers. The diagnosis and treatment of metastatic bone tumors involves multiple modalities and disciplines. In order to facilitate patients’ consultation and rational clinical treatment, it is necessary to make a generalized introduction to its imaging diagnosis and clinical treatment. Computed tomography (PET/CT). 1.X-ray radiograph The most basic judgment of metastatic bone tumor and primary bone tumor can be made based on the patient’s age, medical history, bone lesion location and the form of bone destruction. Take metastatic tumor of long bone as an example, its typical manifestations are: located at the end of long bone; the range of longitudinal intramedullary destruction is larger than the range of transverse diameter; when located in cortical bone, it mostly occurs at the trophoblastic artery, resulting in shallow disc-shaped bone cortical destruction; most soft tissue masses are not large, but patients with late diagnosis may have huge soft tissue masses. The forms of bone destruction are mainly map-like, worm-like and chisel-like, and represent progressively more aggressive and faster growing tumors. Osteogenic or osteolytic destruction depends on the nature of the primary tumor and the response of the bone tissue to the cancer. The primary tumors showing osteogenic reaction include prostate cancer and digestive tract tumors; osteolytic lesions are commonly seen in kidney cancer, myeloma, breast cancer and lung cancer; mixed lesions are seen in breast cancer, digestive tract tumors and reproductive system tumors. 2.CT examination is better than X-ray plain film in determining bone destruction. Through the bone window and enhancement scan, the degree and scope of bone destruction, the scope of soft tissue mass and the anatomical relationship with adjacent blood vessels can be clearly evaluated. The “ring enhancement sign” of the Zengqiang scan can identify the bone destruction caused by bone infection. 3.MRI can detect metastases early and provide soft tissue and three-dimensional anatomy, which can help to determine the extent of infiltration of medullary lesions. However, because of its high sensitivity and false positives, it needs to be confirmed in combination with other examinations. 4.Bone scan is one of the best examinations for early detection of advanced bone metastases, especially when it is difficult to detect by X-ray plain film. Some reports suggest that bone scan detects bone metastases 2-18 months earlier than plain radiographs. However, because this technique is based on the identification of osteoblast activity in the involved bone rather than the actual tumor, early metastases may be missed. In addition, because of its poor specificity, it requires an experienced physician and combined with other relevant information for comprehensive judgment. 5.PET-CT can detect bone metastases earlier and more accurately, but it is expensive. Clinical diagnosis Metastatic bone tumors usually have pain as the main symptom, especially aggravated at night, and multiple sites may have symptoms at the same time. Clinical diagnosis needs to be combined with patient’s medical history, symptoms, laboratory tests, imaging tests and even biopsy. Internal medicine treatment Usually the internal medicine treatment of metastatic line bone tumor includes anti-tumor therapy (such as endocrine therapy, chemotherapy, etc.), bisphosphonate therapy, analgesic therapy, radionuclide therapy, etc. In terms of anti-tumor therapy, specific therapeutic drugs and programs should be used for different primary tumors. 2. In bisphosphonate therapy, these drugs can inhibit osteoclast-mediated bone resorption, inhibit the maturation and function of osteoclasts, inhibit tumor cell spreading, infiltration and bone matrix adhesion and other mechanisms to play a therapeutic role. Indications include: hypercalcemia; bone pain; treatment and prevention of bone-related events (SRE, including pathological fractures, bone marrow compression, hypercalcemia, bone radiotherapy for pain relief, bone surgery for prevention or treatment of spinal cord compression and pathological fractures). In clinical practice, it is recommended that bisphosphonates should be administered for at least 6 months and long-term use is advocated depending on the patient’s benefit, and sometimes the drug may become the only systemic agent for patients with advanced bone metastases. The first generation bisphosphonate is disodium clodronate, and the usage and dosage is 1600 mg/day orally. It is recommended to be swallowed whole, to avoid taking it with calcium or other divalent cationic foods or medications, and to ensure adequate water intake during treatment. Second generation bisphosphonates include pamidronate and alendronate, which are stronger than the first generation drugs in inhibiting bone resorption, and the usage is 60-90 mg of pamidronate over 2 hours intravenously once every 3-4 weeks. Third-generation bisphosphonates include zoledronic acid and ibandronate, and are administered as zoledronic acid 4 mg over 15 minutes intravenously once every 3-4 weeks and ibandronate 6 mg over 15 minutes intravenously once every 3-4 weeks. Precautions include checking the patient’s serum electrolytes and renal function before use, paying attention to oral hygiene and regular monitoring. 3.In terms of analgesic treatment, the WHO guiding principles of three-step analgesia for cancer should be followed: preferred oral and non-invasive routes of administration, administered in steps, administered on time, individualized, and with attention to details. 4. When there is no obvious efficacy by traditional analgesic drugs and local or hemi-radiotherapy, radiopharmaceuticals such as 89Sr or 153Sm should be considered for the treatment of multiple metastatic bone pain. This drug is suitable for osteogenic lesions due to metastatic breast cancer, hormone-resistant prostate cancer or lung cancer. Patient selection should take into account bone marrow function, physical status, recent use of bone marrow inhibitors (chemotherapy or radiotherapy), indications for alternating palliative interventions, and life expectancy. The choice of radiopharmaceuticals is best based on multidisciplinary (radiation oncology, nuclear medicine, drug oncology, etc.) assessment of the patient’s condition. Surgical treatment is aimed at relieving pain, re-establishing motor function and facilitating post-treatment radiotherapy and life care. This treatment is generally suitable for patients with moderate malignant primary tumors (especially prostate cancer); long tumor-free period after primary tumor treatment (kidney cancer, breast cancer, thyroid cancer); limited osteolytic lesions and increased bone density after systemic treatment; isolated bone metastases; good general condition and no contraindication to surgery.