Circulating tumor cells (CTCs) in patients with breast cancer can be regarded as the pre-stadium of clinically manifest distant metastases. Here we present results on CTCs determination in peripheral blood (PB) of breast cancer patients in the context of treatment.Ninety-two patients were enrolled onto a prospective, unicenter study and 71 of those subjects are the focus of our analyses. The differential prognostic and overall survival showed between patients with and without elevated CTCs before and at the end of chemotherapy, is of special interest in patients without clinical evidence of metastasis.