ABSTRACT
PURPOSE: Bone is the most common site of breast cancer metastasis. The aim of this study is to identify the subgroup of patients who have high risk of bone metastasis and we evaluate the prognostic factors of overall survival after bone relapse. METHODS: A total 2,785 of primary breast cancer patients who were treated from January 1980 to December 2001 were included in this analysis. All the patients received radical surgery at the time of diagnosis. We retrospectively collected the clinico-pathologic data (age, tumor size, axillary lymph node status, histologic grade, steroid hormone receptor status, and disease-free interval after primary surgery). Definitive radiologic evidence of bone metastases by plain X-ray or whole body bone scan during follow-up was defined as bone metastases. We analyzed the relationship between the clinicopatholgic factors and the risk of bone metastases and the overall survival after bone relapse. RESULTS: During follow-up, 256 patients (9.3%) experienced bone metastasis. By multivariate analysis using Cox's model, age less than 35 years (p<0.001, risk ratio [RR]; 2.467, 95% confidence interval [CI]; 1.619-3.759), large primary tumor more than 2 cm (p=0.005, RR; 1.911, 95% CI; 1.222-2.988), positive axillary node (p<0.001, RR; 2.798, 95% CI; 1.867-4.195), and a high histologic grade (p=0.046, RR; 1.631, 95% CI; 1.008-2.640) were significantly associated with frequent bone metastases. The 10 years survival rate after bone metastasis was 26.9%. Disease free interval less than 2 years (p<0.001, RR; 3.453, 95% CI; 2.382-5.005) and hormone receptor status (p=0.003, RR; 1.791, 95% CI; 1.218-2.635) were independently associated with poor overall survival after bone relapse. CONCLUSION: We concluded that a shorter disease-free interval after definitive surgery and hormonal receptor status of the primary tumor are independent prognostic factors of overall survival after bone metastasis. These results show that a tailored strategy is needed for the treatment of patients with bone metastases.