BACKGROUNDThe purpose of this cross-sectional study was to evaluate the value of serum tartrate-resistant acid phosphatase 5b (TRACP 5b) and carboxyterminal telopeptide of type I collagen (ICTP) separately and in combination as markers of bone metastases compared to total alkaline phosphatase (tALP) in breast cancer.MATERIALS AND METHODSTwo groups of patients were studied, one with verfied bone metastases (N=46) and one without bone metastases (N=141). Bone marker levels were correlated with the presence or absence of bone metastases.RESULTSSerum TRACP 5b concentrations exhibited the largest area under the receiver-operating characteristics (ROC) curve (AUC=0.845), followed by ICTP (0.818) and tALP (0.814) when all patients were included in the analysis. With the combination of TRACP 5b and ICTP, the AUC increased to 0.881. In multivariate regression analysis, all three markers were significant predictors of bone metastases.CONCLUSIONSerum TRACP 5b, ICTP and tALP exhibited equal performances in the detection of bone metastases. The combination of TRACP with ICTP did not significantly improve the detection of bone metastases over tALP.