Post-operative breast cancer patients diagnosed with skeletal metastasis without bone pain had fewer skeletal-related events and deaths than those with bone pain

BACKGROUND: Skeletal metastases are often accompanied by bone pain. To investigate the clinical meaning of bone pain associated with skeletal metastasis in breast cancer patients after surgery, we explored whether the presence of bone pain was due to skeletal-related events (SREs) or survival (cause specific death, CSD), retrospectively. METHODS: Consecutive breast cancer patients undergoing surgery between 1988 and 1998 were examined for signs of skeletal metastasis until December 2006. Patients who were diagnosed as having skeletal metastasis were the subjects of this study. Bone scans were performed annually for 5, 7 or 10 years; they were also conducted if skeletal metastasis was suspected. Data concerning bone pain and tumor markers at the time of skeletal metastasis diagnosis, and data relating to various factors including tumors, lymph nodes and hormone receptors at the time of surgery, were investigated. The relationships between factors such as bone pain, SRE and CSD were analyzed using the Kaplan-Meier method and Cox's analysis. RESULTS: Skeletal metastasis occurred in 668 patients but the pain status of two patients was unknown, therefore 666 patients were included in the study. At the time of skeletal metastasis diagnosis 270 patients complained of pain; however, 396 patients did not. Analysis of data using Cox's and Kaplan-Meier methods demonstrated that patients without pain had fewer SREs and better survival rates than those with pain. Hazard ratios regarding SRE (base = patients without pain) were 2.331 in univariate analysis and 2.243 in multivariate analysis. Hazard ratios regarding CSD (base = patients without pain) were 1.441 in univariate analysis and 1.535 in multivariate analysis. Similar results were obtained when analyses were carried out using the date of surgery as the starting point. CONCLUSION: Bone pain at diagnosis of skeletal metastasis was an indicator of increased SRE and CSD. However, these data did not support recommendations of follow-up bone surveys in breast cancer patients.