More recent improvement of the risk
assessment is obtained through the molecular
characterization of the tumor and identifies patients
who are predicted to obtain the most therapeutic benefit
[7-15]. These methods identify genetic phenotypes with
a higher likelihood for micrometastasis that can lead to
disease recurrence. Detection of the actual presence of
tumor cells beyond the primary tumor is preferred, but
may not be sufficient, as one cannot distinguish between
dormant tumor cells and those giving rise to recurrence
of the disease [16,17]. The presence of micrometastases
in bone marrow of breast cancer patients is associated
with an increased risk for disease recurrence and death
[18,19]. Detection of bone marrow micrometastasis has,
however, not been adapted as standard in clinical practice
[20]. A more attractive approach for the detection
of the presence of tumor cells beyond the primary
tumor is the detection of circulating tumor cells (CTC).