The influence of breast cancer subtype on bone metastases development and survival in women with metastatic breast cancer

Background: Tumour metastatic disease reflects a complex interplay between tumour characteristics and local host factors. This complex relationship may have an influence on the development of metastatic disease and patient survival. Multiple factors of the primary tumour influence the development of metastases and survival in patients. Breast cancer subtype has been shown to influence patient prognosis and response to therapy. Aim: The aim of our study was to correlate breast cancer subtype with bony metastatic disease and patient survival. Methods: All women undergoing breast cancer surgery in a single institution in Ireland between January 1990 and July 2012 were included in the study. A prospectively maintained database was reviewed and expanded retrospectively. Univariate and multivariate analysis was carried out. Results: Database interrogation identified 238 patients for inclusion. Patient demographics, tumour characteristics and survival data were analyzed. Average follow-up of patients was 57.6 months (range 1–272 months). Multivariate analysis identified oestrogen receptor positivity and presence of metastatic disease elsewhere as significant factors influencing the development of bone metastases. Breast cancer subtype did not influence the bone metastases development (p = 0.99). Breast cancer subtype influenced patients’ overall survival (p < 0.001), bone disease-free survival (p < 0.001) and survival with bone disease (p < 0.001). Subtype did not influence distant disease-free survival. Conclusion: Breast cancer subtype influences patients’ overall survival, with luminal A and B subtypes associated with the best outcome. Bone metastases remain the most common form of breast cancer metastases but are not influenced by breast cancer subtype.