The purpose of this study is to identify potential risk factors for and determine the rate of pathological fracture for patients which having spine metastases from breast cancer and be defined as potentially unstable (SINS 7-12) according to the Spinal Instability Neoplastic Score (SINS). The investigators' analysis will provide robust data about the development of spinal instability and help identify the optimal timing of local surgery treatment.

Considering the concept of spinal instability remains important in the clinical decision-making process for patients with spine metastases, the Spine Oncology Study Group (SOSG) devised an 18-point SINS, which proved reliable and has been widely used in clinical practice. Scores of 0-6, 7-12, 13-18 are considered stable, potentially unstable, and unstable, respectively. Lesions with a low SINS (score 0-6) do not requires surgical interventions, whereas a high SINS (score 13-18) predicts the need for surgical stabilization to restore spinal stability. However, treatment strategy of intermediate SINS (score 7-12) lesions remains ambiguous owing to the uncertainty of spinal stability. With the duration of spinal metastases, some potentially unstable lesions turn to be stable while some turn to be unstable, and several factors such as tumor involvement for vertebral body, radiotherapy may account for different outcomes. Owing to the relatively weaker growth and invasion ability of breast cancer cells compared to other solid tumors such as lung cancer and liver cancer, patients with breast cancer and spinal metastases have longer life expectancy. Reasonable and prompt local surgical intervention to restore spinal stability can achieve pain relief and better quality of life effectively. Moreover, most spinal metastases from breast cancer show lytic or mixed lytic-blastic bone lesions, which exacerbates the spinal stability and results in pathological fracture. Thus, investigators focus on patients which having spinal metastases from breast cancer and an intermediate SINS (score 7-12) to explore the rate of pathological fracture and relevant risk factors. This study will help spine surgeon to identify who could benefit from a prophylactic stabilization procedure with high risk of pathological fracture and when is the best timing of surgery.

Inclusion Criteria:

• Age 18-65 years, female
• Had a histological confirmation of breast cancer, including all pathological types
• Had a histological or radiological confirmation of spinal metastases from breast cancer
• SINS 7-12

Exclusion Criteria:

• Prior prophylactic stabilization surgery to the spine at current level of interest
• Patients with other malignancies except breast cancer
• Misdiagnosis of spinal metastases from breast cancer confirmed by pathological examination
• Patients without undergoing follow-up on schedule
• Withdraw from the study for any reason

A total of 120 patients with potentially unstable spinal metastases of breast cancer will be enrolled