OBJECTIVES: Circulating tumour cells (CTCs) in the blood can give important information about the prognosis and treatment options for cancer patients. Methods like cell-search are not sensitive enough because the blood samples are small (7,5 mL). Currently a technique is developed which can separate CTCs from the whole blood and is called the CTC Trap. This study addresses the potential impact of implementing the CTC Trap in addition to currently used imaging techniques in early staging of primary stage I-III breast cancer in women. METHODS: The early staging process has been identified using the Dutch breast cancer guideline. This process is displayed in a decision tree. Three points in this process have been identified as possible implementation options for the CTC Trap. A simulation model has been built in Excel to simulate the cost-effectiveness of implementing the CTC Trap at these three different points. RESULTS: Potentially relevant points for the CTC trap are: 1) following negative sentinel lymph node procedure to test for micro metastases, 2) following negative result of initial MRI to test for (micro-) metastases, 3) following negative results of further imaging. Usual care resulted in an average survival of 2,42 years, a 3-year survival of 93,71%, 1,51 QALYs and a cost of € 992,56. When implemented at all 3 implementation points simultaneously CTC Trap resulted in an average survival of 2,84 years, a 3-year survival of 97,46 %, 1,84 QALYS and a total cost of € 6.035,45. CONCLUSIONS: CTCs clearly have the potential to improve overall survival. Use of CTCs can potentially improve survival with 0,42 years and improve QALYs with 0,34. Costs do increase at all options but from a health economic perspective it is most valuable to implement CTC Trap in option 1) following negative sentinel lymph node procedure to test for (micro-) metastases.