The assessment of circulating tumor cells (CTCs) has been shown to enable monitoring of treatment response and early detection of metastatic breast cancer (MBC) recurrence. The aim of this study was to compare a well-established CTC detection method based on immunomagnetic isolation with a new, filtration-based platform. | Filtration based assessment of CTCs and CellSearch based assessment are both powerful predictors of prognosis for metastatic breast cancer patients