Risk stratification for predicting symptomatic skeletal events (SSEs) in breast cancer patients with bone metastases

Background Symptomatic skeletal events (SSEs) affect many patients with bone metastases from breast cancer. However, predictive models of SSEs in patients with bone metastases from breast cancer have not been established for clinical use. The purpose of this study is to examine risk factors for SSEs in those patients and by combining these risk factors patients are classified into several groups. With this risk-stratification model, we can identify patients at higher risk of SSEs and require close follow-up to maintain ADL. Methods Participants included 189 female patients with bone metastases from breast cancer and treated in our institute between 2009 and 2012. To assess risk factors for the first SSEs, clinical data at the time of registration were assessed. To estimate the effects of covariates, we used cause-specific hazard modeling. Results Multivariate analysis revealed that a high number of metastasized vertebral bodies (≥20) (p < 0.001) and elevated carcinoembryonic antigen (CEA) level (>5 ng/mL) (p = 0.003) were risk factors for SSEs. Patients were classified into four subgroups according to the combination of the number of vertebral metastases and CEA level: patients with CEA level > 5 ng/mL and ≥20 vertebral metastases; patients with CEA level ≤ 5 ng/mL and ≥20 vertebral metastases; patients with CEA level > 5 ng/mL and <20 vertebral metastases; and patients with CEA level ≤ 5 ng/mL and <20 vertebral metastases. Cumulative incidences of SSEs in these four subgroups at 6 months were 35.6%, 15.6%, 9.3%, and 3.7%, respectively. Conclusions Patients with elevated CEA level (>5 ng/mL) and extensive vertebral metastases (≥20) should be closely monitored in routine clinical care, to allow prevention of pathological fracture or paraplegia with the intervention of orthopedists or radiologists.