Objective  To examine the relationship of clinicopathological features and treatment strategies with the prognosis of patients with initially diagnosed stage Ⅳ breast cancer bone metastasis (IDBCBM).

  Methods  Clinical data from 74 patients with IDBCBM who were treated at Tianjin Medical University Cancer Institute and Hospital between March 2007 and November 2016 were analyzed retrospectively. A univariate analysis of prognosis was conducted using a Log-rank test, and the subsequent multivariate analysis was conducted using a Cox regression model.

  Results  The median age of the patients was 53.3 years. The median total survival duration (overall survival, OS) was 34.3 months, and the 3- and 5-year survival rates were 37.8% and 12.2%, respectively. Patients for whom the first distant metastasis was bone metastasis only had a better prognosis, with a median survival duration of 41.7 months and overall 3- and 5-year survival rates of 54.5% and 20.4%, respectively. In the univariate analysis, molecular subtype, hormonal receptor status, HER-2 expression levels, nodal status, Ki- 67 index, number of bone metastases (NBM), initial mode of metastasis, mode of therapy, and locoregional treatment showed an association with prognosis. Further, multivariate analysis demonstrated that Ki-67 index, NBM, mode of therapy, and initial mode of metastasis were independent factors affecting OS (P < 0.05).

  Conclusions  A high Ki-67 index, single mode therapy, the presence of multiple bone metastases, and accompanying visceral metastasis were associated with a poor prognosis. However, it remains unclear whether locoregional treatment, including surgery and radiotherapy treatment of the primary tumor, is beneficial.