(1) Main Purpose: To observe the clinical efficacy of zoledronic acid regularly in the prevention of SREs in breast cancer patients with bone metastasis (2) Secondary Objectives:~To observe whether zoledronic acid prolonged the time of first SREs in patients with bone metastasis;~The clinical efficacy and influencing factors of zoledronic acid in different subgroups were observed by subgroup analysis of population baseline, clinical characteristics (such as different types of breast cancer), past history and complications.~To observe the clinical distribution, characteristics, timing and compliance of zoledronic acid administration in Chinese breast cancer patients with first bone metastasis.
non-intervention、real world study； Effect of timing and regular treatment of zoledronic acid on the incidence of SREs in breast cancer patients