OBJECTIVES: Research has shown that circulating tumor cells (CTCs) in the blood can give valuable information about the prognosis and treatment options in oncology.  A new approach, CTC therapeutic apheresis (CTCtrap) is being developed for use in breast and prostate cancer. At the moment it is not clear where in the diagnostic track CTCtrap could be of most value. The goal of this study is to estimate the health impact of using CTCtrap in (1) screening for breast cancer, (2) early staging of tumors and (3) therapy response monitoring. METHODS:  A systematic literature study and experts’ interviews were used to document the diagnostic track in breast cancer. Headroom analysis and early health economic modelling was used to estimate the health impact of implementing CTCtrap at the three different purposes.  RESULTS:  Dependent on the assumption of sensitivity, the CTCtrap could decrease the total screening costs. Yet, it is expected that this application only has limited clinical utility. In the early staging, the CTC trap can replace the currently used FDG-PET-CT. The CTCtrap could provide additional staging information and therapy can be selected more specifically, eliminating unnecessary costs. Finally, CTCtrap as a monitoring tool enables personalising therapy by analysing discordance in hormone receptor (HR) and Human Epidermal Growth Factor Receptor 2 (HER2) expression in CTCs compared to solid tumors in metastatic breast cancer patients. It is estimated that in total 4,41% of metastatic breast cancer patients could be treated in a more efficient way, leading to increase in progression free survival of 5,59 months. Increase in clinical utility is expected to be the most important consequence of this implementation option. CONCLUSIONS: CTCtrap as a monitoring tool is expected to be of most value. In this stage, a more appropropiate prescription of expensive therapies can be administered to patients who are sensitive for these therapies.