Abstract: Objective To investigate the expression of circulating tumor cells in metastatic breast cancer and its relatonship with CEA,CA153 and CA125.Methods The Cell Search system was used to detect the expressions of CTCs before new line therapy,meanwhile the electrochemiluminescence was used to detect the expression of CEA,C153 and CA125 in 93 patients with metastatic breast cancer.Results 60%(56/93)metastatic breast cancer patients with ≥1 CTC/7.5mL at baseline.The CTC positivity was not correlated with hormone receptor status,Her-2 status,lines of previous treatment and visceral metastasis.The CEA positivity was 56%(52/93).It was associated with ER or PR-positive(χ²=4.550,P=0.045),and was not correlated with Her-2 status,lines of previous treatment and visceral metastasis.CA153 positivity was 47%(44/93).It was not correlated with hormone receptor status,Her-2 status,lines of previous treatment and visceral metastasis.CA125 positivity was 41%(38/93),and it was associated with over one-line previous treatment(χ²=4.501,P=0.038),However,CA125 positivity was not correlated with hormone receptor status,Her-2′s status and visceral metastasis.The CTC was positively correlated with CEA(r=0.296,P=0.004).It was positively correlated with CA153(r=0.286,P=0.005),and not correlated with CA125(r=0.184,P=0.077).Conclusion The circulating tumor cells(CTCs)positivity was high in patients with metastatic breast cancer,but also its positivity has correlation with CEA and CA153.Our study indicated that detection of circulating tumor cells combination with CEA and CA153 in metastatic breast cancer may be helpful for therapy,meanwhile the CTC may become a potential therapy target for metastatic breast cancer.